Verifiable and remediable dry-tomb biolandfills and construction methods for biological carbon sequestration

Abstract

The present invention relates to a dry tomb-type landfill for biological carbon sequestration, and more particularly to a dry tomb-type biolandfill having a biomass enclosed by top and bottom seals containing at least one barrier to water transport, a cover layer that functions to protect the enclosed biomass from atmospheric disturbances, one or more accessible pipes or conduits connected to the enclosed biomass, and a means for monitoring biomass decomposition of the enclosed biomass.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Provisional Patent Application No. 63 / 432,031 (filed December 12, 2022) and Utility Nonprovisional Patent Application No. 18 / 316,103 (filed May 11, 2023). [Background technology]

[0002] Climate science scenarios that limit global temperature rise to less than 2°C by the end of this generation require carbon-negative options that remove CO2 from the atmosphere. One approach to carbon negativity is to capture and store organic carbon, which is photosynthetically converted from atmospheric CO2 in growing plants and trees. It has long been recognized that the amount of carbon that can be captured from agriculture and forestry is sufficient to offset global warming ("Can We Control The Carbon Dioxide In The Atmosphere?", Freeman J. Dyson, Energy Vol. 2 PP 217-291. Pergamon Press 1977).

[0003] Schemes involve growing ephemeral plants that turn into humus or accumulate in artificial peat bogs ("Can We Control The Carbon Dioxide In The Atmosphere?", Freeman J. Dyson, Energy Vol. 2 PP 217-291. Pergamon Press 1977), or harvesting woody biomass and burying it in trenches beneath a layer of soil ("Carbon sequestration via wood burial", Ning Zeng, Carbon Balance Management 3, 1 2008, https: / / doi.org / 10.1186 / 1750-0680-3-1). In both of these approaches, the harvested biomass is stored in a moist, anaerobic environment (due to intrusion of groundwater) where part of the biomass decomposes anaerobically, releasing CO2 and methane. The IPCC estimates that 50% of wood decomposes in a moist, buried environment, releasing large amounts of methane, making storage a net greenhouse gas emitter rather than an offsetting technology. Lower estimates of greenhouse gas emissions have been published for the wet anaerobic decomposition of wood, estimating that wet anaerobic storage is greenhouse gas neutral ("Anaerobic biodegradability of wood: a preliminary review," M. Milke, Y. Fang, S. John, 2010 Water New Zealand Annual Conference, 22–24 September 2010, Christchurch, New Zealand). In all cases, due to methane emissions, simple anaerobic storage of woody biomass in a moist, anaerobic environment is not a realistic solution to global warming. However, solutions that store biomass and prevent rapid decomposition have the potential to offset a significant portion of global CO2 emissions. Almost equally important is finding a solution that allows the decomposition of stored biomass to be monitored, verifiable, and, if necessary, repairable. This invention provides unexpected solutions to both problems.

[0004] To give some perspective, with harvested biomass having a carbon content of 50% by weight and an annual crop yield of 10 dry metric tons per acre, a successful technology to offset about one-quarter of global greenhouse gas emissions (roughly equivalent to 10 gigatonnes of CO2 equivalent per year) would require approximately 6-10 8 acres, or about 2.5 10 6 kilometers 2 Significant agricultural production would be required. In this hypothetical scenario, about 17% of the land used to grow row crops (wheat, corn, etc.), or about 5% of the Earth's forest land, or 7% of the Earth's plantations and pastures. By comparison, many integrated assessment models presented by the IPCC estimate a net loss of about 12% of the land used to grow row crops (wheat, corn, etc.), distributed between forests and bioenergy crops by about 2100. 6 kilometers 2 This would require an increase in the amount of land used for biofuel production. Integrated assessment models reported by the IPCC suggest that such large acreage numbers would come primarily from reductions in pasture and cropland, with only minor reductions in a category called "natural land," which roughly corresponds to shrubland in other inventories of global land use. While the amount of land required to offset one-quarter of global greenhouse gas emissions is substantial, deployment on this scale is feasible if significant atmospheric carbon reductions are desired by the international community. Summary of the Invention

[0005] The present invention relates to a verifiable dry tomb biolandfill having biomass enclosed by top and bottom seals containing at least one barrier to water transport forming a dry tomb structure, a cover layer comprising soil that functions to protect the enclosed biomass from atmospheric disturbances, one or more accessible and sealable true-wall pipes or conduits connected to the enclosed biomass, and a means for monitoring biomass decomposition of the enclosed biomass.

[0006] The following figures are included to illustrate certain aspects of the embodiments and should not be construed as limiting the embodiments. [Brief explanation of the drawings]

[0007] [Figure 1] Shown are elements of a verifiable and repairable dry tomb biolandfill constructed at the surface, containing a dry tomb structure formed by top and bottom seals containing a single water transport barrier that encloses the dry biomass, with a sealable coaxial pipe structure connecting the dry tomb to the surface of the biolandfill. [Figure 2] Illustrated are elements of a verifiable and remediable dry tomb biolandfill constructed at surface containing dry tomb structures and biomass, with top and bottom seals containing two nested water transport barriers separated by a sealable coaxial pipe structure and a spacer structure that encloses the dry biomass. [Figure 3] Elements of a verifiable and remediable dry tomb biolandfill constructed on a dry tomb structure and biomass-containing surface are shown, with top and bottom seals containing two nested water transport barriers separated by two spatially separated sealable pipe and spacer structures. [Figure 4] A detailed view of the configuration of the layers covering the top of a verifiable and repairable dry tomb-type biolandfill with top and bottom seals containing two nested water transport barriers separated by a spacer structure is shown. [Figure 5] A detailed view of the configuration of layers near the bottom of a verifiable and repairable dry tomb-type biolandfill with top and bottom seals containing two nested water transport barriers separated by a spacer structure is shown. [Figure 6] Elements of a verifiable and remediable dry tomb biolandfill are shown, including a dry tomb structure and biomass containing biomass constructed at the base below ground surface with two nested water transport barriers separated by spacers and multiple sealable pipes connecting the dry tomb structure to the surface. [Figure 7] A graph showing the water adsorption branching isotherms at 25°C for average values ​​of Miscanthus sinensis, prairie cordgrass, and 10 species of broad-leaved trees. [Figure 8] 1 shows graphs of the isotherms of the water adsorption branch of Miscanthus at 20°C, 25°C, and 4°C. [Figure 9] 1 shows a graph of how water activity is affected by rain weight fraction and water weight fraction in dry biomass. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention relates to the sequestration of biogenic carbon, which is produced and stored by plants on Earth as a natural result of their photosynthetic life cycle. For purposes of the present invention, the biogenic carbon is harvested as biomass when the plant reaches the end of its carbon life cycle and before it decomposes. In some embodiments, the biomass is processed to produce other products, such as gaseous and liquid fuels, and a portion of the biogenic carbon remains unconverted but may be chemically modified. This fraction of biogenic carbon is also referred to as biomass, or in some cases, chemically modified biomass.

[0009] The present invention is a biolandfill composition that provides a means to safely, verifiably, efficiently, and economically store carbon in biomass without significant decomposition for hundreds of thousands of years, helping to offset CO2 emissions and mitigating climate change. The biolandfill composition allows for the storage of biomass in a dry environment that mitigates the decomposition process, along with a means to verify whether water has entered the biolandfill and whether there is significant generation of CO2 and / or methane greenhouse gases from biomass decomposition. In a preferred embodiment, if unacceptable water content or greenhouse gas generation is detected, a means is provided to restore the tomb environment necessary for biomass storage and further dry the biolandfill.

[0010] The biolandfill contains a dry tomb structure containing biomass with top and bottom seals containing at least one barrier to water transport that completely surrounds the biomass. This dry tomb structure is also referred to as a dry tomb. The level of dryness can be quantified by the water activity of the gas contained within the dry tomb structure. In a preferred embodiment, the biomass within the dry tomb has a low moisture content. The biolandfill has one or more sealable pipes or conduits with solid walls that connect the interior of the dry tomb with the Earth's atmosphere. In a preferred embodiment, the pipe or conduit seal is a valve that can be opened but remains closed most of the time, isolating the environment within the dry tomb from the Earth's atmosphere. In some cases, the sealable pipe or conduit is referred to as a pipe or conduit. If a design using top and bottom seals containing a single water barrier surrounding the dry biomass is adopted, considerable care must be taken in the construction of the barrier to ensure it remains impermeable. There is a small probability of a small defect in a single water barrier structure, so in a preferred embodiment, an additional element is incorporated into the biolandfill to allow for the purging of water vapor and any other unwanted gas species from the dry tomb structure. To provide purging, at least two sealable pipes or conduits are incorporated into the biolandfill design, open for purging in such a way that gas can enter one pipe or conduit and exit the other, purging some of the gas within the dry tomb structure. Purging with relatively dry gas allows the biolandfill to dry out as the wet gas leaves. This addition of two or more sealable pipes or conduits provides a means to dry out and therefore repair (if necessary) the storage conditions of the biomass in the biolandfill; this type of biolandfill is referred to as a "verifiable and repairable biolandfill." A biolandfill constructed with a single pipe or conduit connecting the interior of the dry tomb with the Earth's atmosphere is referred to as a "verifiable biolandfill."In one embodiment of a verifiable and repairable biolandfill, the sealable pipes or conduits connecting to the surface run coaxially, and when opened for purging, the purge between them flows primarily vertically. In another embodiment of a verifiable and repairable biolandfill, two or more sealable pipes or conduits are spatially separated, and when opened for purging, the purge direction has a significant horizontal component. This type of dry purge is not characteristic of public landfills that store all wet waste. Gas component measurements should ideally be performed in a verifiable and repairable biolandfill during purging and designed to assess CO2, methane, and water vapor concentrations in the gas exiting the biolandfill. In a verifiable biolandfill without purging, gas components can most easily be measured as gas pressure builds within the dry tomb and some gas escapes the open pipe or conduit. For gas component measurements performed with flowing gas, at least one gas analyzer should be temporarily connected or permanently installed to at least one of the pipes or conduits. The connections can be such that all or a portion of the gases exiting the pipe or conduit flow through the analyzer. A wide variety of gas analyzers are commercially available, and in some cases, analyzers that measure a subset of CO2, methane, and water vapor can be used. When using an analyzer that measures a subset of CO2, methane, and water vapor, it is preferable to utilize an additional analyzer that completes the entire measurement set (i.e., CO2, methane, and water vapor). Furthermore, it is advantageous to measure the gas flow rate from any pipe or conduit, as well as the gas purge flow rate into any pipe or conduit. When gas purging or sampling is not occurring, the pipe or conduit can be closed off from the Earth's atmosphere. In this simplest embodiment, the environment within the biolandfill is aerobic after construction and transitions to a mostly anaerobic environment over a period of time. In a verifiable and remediable biolandfill, a portion will cycle between aerobic, anoxic, and anaerobic conditions due to air intrusion during gas sampling, purging, or potential remediation operations.In one embodiment, which may be a feature of both verifiable biolandfills and verifiable and repairable biolandfills, pressure within closed, sealable pipes or conduits is measured to assess whether gas is dissipating from the buried biomass. In this embodiment, a readable analog or digital pressure gauge is installed in at least one of the sealable pipes or conduits. The pressure gauge's accuracy is preferably 0.01 bar, more preferably 0.001 bar. The pressure gauge's range should be at least 1-1.2 bar, more preferably 0.75-2 bar. In another embodiment, the biomass within the dry tomb structure is compartmentalized with a secondary or tertiary water barrier that contains the partitioned biomass. This arrangement provides additional protection to keep the biomass dry during construction of the biolandfill and throughout the life of the dry tomb structure. In another embodiment, which may be a feature of both verifiable biolandfills and verifiable and remediable biolandfills, if excessive unwanted decomposition of buried biomass occurs, the biogas produced is bled out of the biolandfill and utilized in a combustion process or treated so that at least a portion of the evolved greenhouse gases are captured and sequestered. An optional embodiment has a pipe running to the base of the dry tomb structure that can be used to pump out small amounts of liquid water that may accumulate if there are unexpected defects in the biolandfill construction.

[0011] A preferred embodiment has multiple nested water transport barriers that contain multiple water transport barriers nested within each other to isolate biomass. This reduces the probability of random defect alignment and significantly reduces net water permeation through the defects into the dry tomb structure. In a preferred embodiment, there is an isolation structure, which is a layer or region between the nested water transport barriers. This isolation structure (layer or region) can improve mechanical stability and mass transfer resistance to water intrusion through the defects. The top and bottom seals form the outermost boundaries of the dry tomb structure, and therefore the dimensions of the dry tomb structure are defined by the outermost dimensions of the top and bottom seals.

[0012] A notable aspect of the present invention is the storage of biomass in a dry environment in a biolandfill that prevents rapid decomposition and greenhouse gas generation. As noted above, the prior art does not adequately address greenhouse gas generation and monitoring. Proposals for simple ground storage of biomass have been shown to be a net greenhouse gas emitter rather than a carbon-negative solution. Ground water supports the growth of microorganisms that invade and decompose biomass, generating greenhouse gases. A measure of the moisture conditions that support microbial growth is water activity. Water activity (a w ) is defined as the ratio of the water vapor pressure in the gas equilibrated with the biomass to the saturated vapor pressure of pure water at the temperature of the stored biomass. Expressed as a percentage, this is approximately the relative humidity. Therefore, a water activity (a w ) is approximately equal to 80% relative humidity, which means that the partial pressure of water vapor in atmospheric gas is 80% of that of pure water. In an aerobic environment, a water activity above 0.95 provides enough moisture to support the growth of bacteria, yeast, and mold. w A reduction in water activity (a) inhibits the growth of such organisms. For foods stored in an aerobic environment, if the water activity of the finished product is controlled at or below 0.85, biological growth is sufficiently reduced that it is not subject to the U.S. Food and Drug Administration's 21 CFR parts 108, 113, and 114. As the water activity is further reduced, fewer and fewer organisms are able to grow. wIt has been shown that organisms disappear when the water activity falls below approximately 0.61 (A. Stevenson et al., "Is there a common water-activity limit for the three domains of life?" The ISME Journal 9, 1333-1351, 2015). As water activity decreases, metabolic rate also decreases. The reason organisms' viability declines as water activity decreases is because, to sustain life, cells must move water-solubilized nutrients inward through their cell walls and water-solubilized waste products outward through their cell walls. Water tightly bound to specific sites cannot function as a solvent; only water sorbed to free or flowing surfaces can solubilize nutrients and waste products. As water activity decreases, water resides only in strongly bound sites, such as hydroxyl groups on polysaccharides, carbonyl and amino groups on proteins, and other sites that can retain water through hydrogen bonds, ion-dipole bonds, or other strong interactions. This binding behavior is called sorption behavior and can be quantified by measuring water sorption isotherms. This same basic behavior occurs in anoxic and anaerobic environments. Microorganisms living in anoxic and anaerobic environments may differ from those living in aerobic environments, but they still require the transport of water-solubilized nutrients and waste products across the cell wall. Thus, the definition of a dry environment is the same for aerobic, anoxic, and anaerobic environments. A more detailed description of dry tomb biolandfills for biological carbon sequestration is provided in co-pending applications Ser. Nos. 63 / 432,031 (filed 12 / 12 / 2022) and 18 / 316,103 (filed May 11, 2023), which are incorporated herein by reference.

[0013] Over time, water activity thermodynamically equilibrates across the bulk of a sealed dry tomb structure. This equilibration results in the same activity for water sorbed on the biomass and water vapor in the gas space. Thus, sampling the gas space from a dry tomb structure that has been allowed time to equilibrate provides a means of measuring water activity. Equilibration times are typically six months, preferably one year, and more preferably two years. A dry environment is defined herein as a water activity in the gas sampled from the biolandfill that is less than 0.85, preferably less than 0.775, more preferably less than 0.75, highly preferably less than 0.65, and most preferably less than 0.6. If sampling is performed during purging, a representative sample should be taken after the volume of gas purged into the biolandfill exceeds 0.0001 of the dry tomb volume and is less than one-tenth of the dry tomb volume. The lower limit is set to ensure sufficient gas flow through the pipe or conduit being sampled. The upper limit is set by the desire for the purge to displace gas from the biolandfill without breaking through the pipe or conduit being sampled. In a more advanced protocol, purge gas breakthrough is assessed using molecular marker species introduced into the purge gas that can be detected by a gas analyzer. Another advanced protocol involves sampling the gas components before they have time to equilibrate (i.e., less than six months after the previous sample) and assessing water activity using a molecular transport model. In another embodiment, the time dependence of water vapor concentration escaping from the biolandfill is used with a model to assess any spatial dependence of water activity within the dry tomb structure. Even without purging, gas components can be easily measured if pressure builds and gas escapes from an open pipe or conduit. Alternatively, a single pipe or conduit can be used to pressurize the biolandfill. Water activity measurements can be performed by allowing the injected gas to equilibrate with the gas in the dry tomb structure and then allowing the gas to escape from the pipe or conduit.

[0014] Organisms living in aerobic, anoxic, and anaerobic environments have metabolic differences. The result of these metabolic differences is that CO2 is released as a greenhouse gas from the decomposition of aerobic biomass, while anaerobic and anoxic environments produce a mixture of CO2 and methane, which is approximately 25 times more potent as a greenhouse gas. Therefore, maintaining a dry environment in the anoxic and anaerobic portions of the biolandfill is important. To keep the biomass dry, the top and bottom seals have at least one water transport barrier that surrounds the biomass contained in the dry tomb structure. This barrier, which completely surrounds the biomass, substantially prevents groundwater from entering. Its function is the opposite of the water transport barriers in conventional municipal and toxic waste landfills. Conventional municipal and toxic waste landfills use a water transport barrier to prevent groundwater contamination by permeating outward from contaminated water contained in the landfill, as opposed to preventing groundwater from permeating inward into the dry biomass.

[0015] In a preferred embodiment, the top and bottom seals contain at least one additional water transport barrier surrounding the biomass. In this embodiment, the top and bottom seals contain nested water transport barriers, with one transport barrier conformally nested inside the other. The advantage of this nested double-barrier structure is that it reduces and / or eliminates the effects of pinholes or defects in the outermost water transport barrier. The occurrence of pinholes and / or defects is extremely rare, and the probability of pinholes or defects lining up in this nested structure is very low. In an even more preferred embodiment, three or more water transport barriers are nested to separate the ground and groundwater from the biomass. For all nested water transport barriers, a spacer structure (layer or region) can be used to separate (i.e., separate) the nested water transport barriers. The spacer or separating structure can include soil, compacted soil, clay, geosynthetic clay, geotextile, geonet, or geosynthetic fabric. In some cases, a high-capacity water adsorbent is incorporated into the spacer structure. In other embodiments, multiple high-capacity water sorbent materials are incorporated into the spacer structure. A high-capacity water sorbent is considered a sorbent that, when exposed to fresh liquid water, has a sorbent loading of greater than 0.5 grams of water per gram of dry sorbent material. An example of a high-capacity water sorbent is a highly adsorbent polymer. The thickness of the spacer structure between the water transport barriers can range from 0.1 centimeters to 3 meters, more preferably from 10 centimeters to 1 meter.

[0016] The only way water can cross a flawless water transport barrier to keep biomass dry for a substantially long period of time, e.g., hundreds to thousands of years, is by slow diffusion (i.e., not convective transport). The rate at which water diffuses through a material or membrane can be quantified by measuring the water (or moisture) vapor transmission rate. The water vapor transmission rate is the amount of water per unit time that passes through a given surface area from one side of the material with high water activity (saturated or nearly saturated) to the other side with low water activity (dry or nearly dry). The units of water (or moisture) vapor transmission rate are g / m 2 / day, and this measure of moisture is used in many industries where moisture control is important, such as food and pharmaceutical packaging. In the United States, g / 100 in2 / day is also used, which is g / m 2 The water (or moisture) vapor transmission rate is 0.064516 (approximately 1 / 15) of the value in units of 1 / day. Water (or moisture) vapor transmission rate is dependent on temperature and water activity. For the metric system, we refer to the measurement at 38°C that a material with a water activity in the range of 0.9 to 1.0 on one side diffusely transmits to the opposite side where the water activity is 0.05 or less. The water (or moisture) vapor transmission rate of a water transport barrier under these test conditions is 0.0 to 0.5 g / m 2 / day, more preferably in the range of 0.0001 to 0.2 g / m 2 / day, more preferably 0.001 to 0.1 g / m 2 / day, most preferably 0.002 to 0.05 g / m 2 / day. Under these measurement (i.e., test) conditions, the water (or moisture) vapor transmission rate is in the range of 0.05 g / m 2A water transport barrier per day would deliver the equivalent of an 18-micron-thick film of water covering the surface of the barrier material over a one-year period. During use, the temperature of the biolandfill is lower than the test conditions, and the difference in water activity across the barrier would significantly reduce the amount of water delivered by a factor ranging from 2 to 200 when comparing the delivery rate at the test conditions with that of a dry tomb structure. Under the test conditions, the water (or moisture) vapor transmission rate is inversely proportional to the thickness of the barrier material (i.e., a doubling of the thickness results in a two-fold decrease in the water (or moisture) vapor transmission rate). If two nested barriers, each with the same permeability as a single barrier, were present, the water delivery rate would decrease by a factor of two if there was no mass transfer resistance in the region between them. In a preferred embodiment within the seal structure, a spacer structure is present that separates the nested water transport barriers, providing significant mass transfer resistance. Depending on the design, this would result in an additional reduction in water transport rate of 1.5 to 4 times. Materials having a water (or moisture) vapor transmission rate within a preferred range for practicing the present invention are plastics including low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, polyester, and oriented polyester sheets with thicknesses of 1 to 300 mils (1 mil = 0.001 inches). Preferred materials are plastic sheets formed from low-density polyethylene resins with densities of 0.91 to 0.94 g / cc and high-density polyethylene resins with densities of 0.94 g / cc or greater. These materials are widely used in public landfills and can be easily joined by plastic welding processes to prevent leakage between sheets.

[0017] Currently, the GM-13 public landfill specification targets products made from low-density polyethylene resins, typically between 0.91 and 0.94 g / cc, while the GM-17 specification targets products made from high-density polyethylene resins, typically with densities of 0.94 g / cc or greater. Historically, higher-density polyethylene (GM-17) has the advantage of greater chemical resistance, while lower-density polyethylene (GM-13) has superior environmental stress cracking performance. Preferred thicknesses for sheets made from low-density and high-density polyethylene resins range from 10 to 300 mils, more preferably from 20 to 150 mils, and even more preferably from 40 to 80 mils. Clay layers (especially bentonite) with thicknesses of 0.2 to 2 meters have water (or moisture) vapor transmission rates within the target range, but are not preferred as water transport barriers. In field settings, significant performance degradation of clay layers has been observed. Deterioration of clay barrier properties is attributed to several factors, including the exchange of sodium ions for calcium ions within the clay structure and the cyclical hydration and dehydration of the clay cap due to weather and other events, which cause cracking. Thin (0.01–0.4 m thick) clay or geosynthetic clay layers have advantageous applications when incorporated as layers separating water transport barriers or between the innermost water transport barrier and biomass. In this role, the clay layer acts as a water adsorbent to remove small amounts of water that pass through the water transport barrier, a weak diffusion barrier to inhibit water transport, and a swelling agent to seal any pinholes in the water transport barrier. Clays can also be used to seal overlapping plastic sheets that are not sealed in the thermal welding process. Highly adsorbent polymers can be used in spacer structures separating nested water transport barriers to prevent water transport. Highly adsorbent polymers can adsorb 100–300 times their dry weight in water. An example of a highly adsorbent polymer is sodium polyacrylate. Other examples are crosslinked polyacrylates and polyacrylamides; cellulose- or starch-acrylonitrile graft copolymers; and crosslinked maleic anhydride copolymers.

[0018] The base of a dry tomb structure in a biolandfill is considered to be approximately the lowest point of any water transport barriers. This base can be located below the ground surface, as in public landfills, or near or at the ground surface. The top surface of a dry tomb structure in a biolandfill is taken to be the top surface of any water transport barriers, and this surface is typically above ground surface. The maximum vertical thickness of biomass between the innermost water transport barriers in a dry tomb structure is at least 2 feet, preferably greater than 10 feet, more preferably greater than 50 feet, and most preferably greater than 100 feet and less than 2,500 feet. The maximum lateral extent of biomass between the innermost water transport barriers in a dry tomb structure, measured in a plane perpendicular to the vertical, is greater than 10 feet, preferably greater than 100 feet, and more preferably greater than 1,000 feet and less than 10,000 feet. Thus, the volume of biomass enclosed in the dry tomb is greater than 355 ft³ (or 10 m³), ​​preferably greater than 3,550 ft³ (or 100 m³), ​​and more preferably greater than 35,550 ft³ (or 1,000 m³). In a preferred embodiment, the base of the dry tomb structure is sloped so that liquid water that accumulates within the structure can be drained at one end, or more preferably, at a point where a pipe or conduit can be used to remove the liquid water. To aid in drainage, a laterally running perforated or porous pipe or conduit can be placed at the bottom of the dry tomb structure near the surface of the innermost water transport barrier. Ideally, the laterally running pipe or conduit discharges the water to a location where it can be collected or accessed by a vertical pipe running to the surface of the biolandfill.

[0019] The top surface of the dry tomb structure within the biolandfill is preferably covered with a thick layer of soil to protect the dry tomb and isolate it from damage caused by the Earth's environment (oxidation by air, wind gusts, roots from plants and trees, lightning, etc.). The thickness of the soil layer covering the dry tomb is preferably at least 2 meters, more preferably greater than 5 meters, and most preferably greater than 10 meters. In a preferred embodiment, the top surface of the dry tomb structure is covered with geonet, geomembrane, geotextile, geocomposite, or other protective sheeting to drain water and provide mechanical protection for the outermost water transport barrier. It is also preferred that the first meter of soil covering the top surface of the dry tomb be free of large stones or boulders. In a preferred embodiment, the top surface of the soil covering the dry tomb, which is exposed to the Earth's atmosphere, has plants, grasses, or shallow-rooted trees growing on it to prevent erosion.

[0020] At least one sealable solid-walled pipe or conduit extends from the interior of the dry tomb structure through the layer of soil covering the tomb to the Earth's atmosphere. In some cases, the sealable solid-walled pipe or conduit is referred to as a sealable pipe or conduit, and in all instances, some means of opening and closing it exists. Preferred embodiments seal these pipes or conduits with openable and closable valves. However, several other removable sealing methods can be used, including threaded caps, flange-mounted caps, and other means of mechanically attaching removable caps. For each pipe or conduit, there is at least one waterproof seal to the water transport barrier, preventing groundwater intrusion. In preferred embodiments, wherever the pipe or conduit contacts the water transport barrier, there is a waterproof seal to the water transport barrier that prevents water intrusion. This sealing keeps the integrity of the water transport barrier intact. Sealing can be achieved by processes such as heat welding, gaskets, or adhesive bonding. The sealable solid-walled pipe or conduit that passes from the interior of the dry tomb structure through the soil layer overlying the tomb to the Earth's atmosphere must have low permeability to water, good corrosion resistance, and good mechanical properties. An example of a material that meets these requirements is PVC pipe. The sealable pipe or conduit must protrude into the dry tomb and be in contact with gases within its interior. Preferably, the sealable pipe or conduit extends into the dry tomb structure at least 2 inches below the top of the innermost water transport barrier, more preferably 1 foot below the top of the innermost water transport barrier. In another preferred embodiment, at least one of the sealable pipes or conduits extends within 4 feet of the innermost water transport barrier near the bottom of the dry tomb structure, more preferably within 2 feet of the innermost water transport barrier near the bottom of the dry tomb structure, and most preferably within 1 foot of the innermost water transport barrier near the bottom of the dry tomb structure.The sealable pipe or conduit has an end that protrudes above the soil layer covering the dry tomb structure and has an atmospheric seal that can be released occasionally to allow gas sampling from the interior of the dry tomb and / or purging with flowing gas introduced into the pipe. An example of a preferred atmospheric seal is a valve. When open, a sealable pipe or conduit connected to the surface atmosphere will supply oxygen to the pipe or conduit, causing a portion of the biolandfill to cycle between anaerobic, anoxic, and oxidative conditions unless oxygen is strictly excluded from the pipe or conduit. Strictly excluding oxygen is very difficult. In principle, this can be done by installing a valve that purges dry nitrogen into the sealable pipe or conduit. This would increase operational costs, and in most situations, it is preferable to use dry air or low-humidity air to purge the pipes or conduits running into the dry tomb structure from the Earth's atmosphere. Atmospheric air can be used as long as the water activity (i.e., relative humidity at the temperature of the landfill) during the air purge is less than 60%, preferably less than 40%, even more preferably less than 20%, and most preferably less than 10%. If an atmospheric purge is used, a portion of the biolandfill will become oxidative and cycle through anoxic and potentially anaerobic conditions over time.

[0021] Within a dry tomb structure, pipes or conduits may be perforated or porous to collect gas from different depths or zones. In most cases, these perforated or porous pipes or conduits are connected (or spliced) to a sealable, solid-walled pipe or conduit that extends from the interior of the dry tomb through the overlying protective soil layer to the Earth's atmosphere. The perforations or porosity may be zoned or over long, continuous lengths. A non-limiting example of perforation is a hole or groove in the pipe that runs through the dry tomb structure. Porosity can be imparted by fabricating lengths of pipe or conduit from a mesh or screen structure. It is also possible to have one or more pipes coaxially running within the outermost pipe, in a manner similar to multiple-completion oil and gas wells. Multiple-completion oil and gas wells can separate production from multiple oil or gas bearing zones (different depths) using parallel tubing strings within a single wellbore casing string. In biolandfills, this type of technology allows a single pipe or conduit with one or more coaxially contained pipes or conduits to purge the dry tomb structure's sweep gas to the surface. It can also be used to measure gas production from different zones (or depths) within the dry tomb structure or to remove liquid water that may accumulate in the dry tomb structure. This is particularly advantageous when the biomass in the dry tomb biolandfill is compartmentalized with secondary or tertiary water barriers that contain the partitioned biomass. In a more preferred embodiment, there are multiple, spatially separated, sealable, solid-walled pipes or conduits extending from the interior of the dry tomb structure through the water barrier(s) and soil layers overlying the tomb to the Earth's atmosphere. This arrangement allows gas to be injected into the dry tomb structure when one or more sealable pipes or conduits are opened, and allows the one or more sealable pipes or conduits used to collect or sample gas that flows primarily horizontally through a portion of the dry tomb.This arrangement can be used to purge selected areas within the dry tomb structure, as well as to create an approximate map of where any biogas is being generated. By placing sealable pipes or conduits far apart, large volumes within the structure can be purged. This allows for effective restoration and repair of the atmospheric conditions of most of the dry tomb structure. Restoration and repair is achieved by purging with low-humidity gas, which is released into the atmosphere as wet gas, reducing the moisture content within the dry tomb structure. To reduce gas pressure drop during purging, it is possible to have perforated or porous pipes or conduits running laterally through the dry tomb structure. Multiple pipes or conduits can also be configured to access different depths (or zones). This is particularly advantageous when the biomass within the dry tomb structure is compartmentalized with secondary or tertiary water barriers to accommodate separate biomass.

[0022] To measure gas composition in a biolandfill, gas is preferably released through an open, sealable pipe or conduit leading to the surface where it can be sampled by analytical equipment. This analytical equipment is connected to the pipe or conduit to measure the composition of CO2, methane, and water vapor. Purging the pipe or conduit allows for a representative measurement of the gas composition within the dry tomb structure. If the biolandfill is properly constructed and operated, the gas pressure increase due to biomass decomposition is small, so little gas flows when the sealable pipe or conduit is open, making purging necessary to accurately measure the composition within the biolandfill. To provide a more continuous measurement of gas evolution, the pressure within the sealable pipe or conduit can be recorded while the biolandfill is sealed from the Earth's atmosphere. For verifiable and remediable biolandfills, if the isolated biomass begins to decompose, purging can be initiated to remediate the atmospheric environment within the dry tomb, and in some extreme cases, liquid water can be pumped from the base of the biolandfill to the surface. Both verifiable and verifiable and remediable biolandfills use sealable pipes or conduits to collect and transport biogas to a treatment facility where it is separated and / or combusted. Ideally, the separation process captures and sequesteres CO2 from the unwanted biogas stream.

[0023] The biomass sequestered in biolandfills can be harvested plants or trees, or chemically altered biomass left as waste from chemical conversion processes. Chemical conversion techniques that produce biomass-derived "waste" include torrefaction, carbonization, anaerobic digestion, and biofuel production. All of these chemically altered materials, along with the harvested plants or trees, are referred to as biomass.

[0024] From an economic perspective, it is preferable to produce feedstock harvested from highly productive plants and trees (often referred to as energy crops) with dry biomass yields ranging from 1 to over 20 metric tons per acre per year. It is also preferable that the sequestered biomass is not a food crop, such as corn, wheat, or other similar plant material. A partial list of crops suitable for producing biomass for the present invention is shown in Table 1. The broad range of crops listed in Table 1 broadens the range of applicability, as these feedstocks can be grown in diverse climates around the world. Furthermore, many of these crops can be grown on marginal or degraded land with reduced yields. Because food crops are not preferably the biomass of choice, impaired soil and irrigation can be used in biomass production. The weight fraction of carbon in the dry biomass of the plants listed in Table 1 ranges from about 40% to about 55% by weight. If the biomass were simply harvested and sequestered in a biolandfill, this would offset about 1.3 to about 1.8 metric tons of CO2 per metric ton of dry biomass sequestered.

[0025] [Table 1-1] [Table 1-2]

[0026] Algae is an additional high-yield biomass that can be used, but due to its composition, it requires special growth and harvesting techniques, as well as very high levels of dryness for storage, making it less preferred, although it falls within the range of potential biomass sources if the aforementioned obstacles are overcome.

[0027] To ensure dryness, biomass (either harvested or chemically altered) should be dry when loaded into the landfill. If there is too much free or sorbed water in the biomass, the water activity of the sealed biolandfill will be too high, leading to biomass decomposition. To meet this requirement, the moisture content of the finished dry tomb structure is preferably less than 20% by weight of the dry weight of the biomass contained within the tomb; in preferred embodiments, the moisture content of the dry tomb structure is less than 15% by weight of the dry weight of the biomass contained within the tomb; in more preferred embodiments, the moisture content of the dry tomb structure is less than 10% by weight of the dry weight of the biomass contained within the tomb; in even more preferred embodiments, the moisture content of the dry tomb structure is less than 8% by weight of the dry weight of the biomass contained within the tomb; and in the most preferred embodiment, the moisture content of the dry tomb structure is less than 4% by weight of the dry weight of the biomass contained within the tomb. Low moisture content leads to low water activity in the biolandfill, and in either case, it is preferable to dry the biomass as much as possible before loading it into the biolandfill. Harvested or chemically altered biomass can have moisture contents much higher than the preferred range, and a drying process is often required. For example, harvested live wood (such as loblolly pine) can have a moisture content ranging from 40% to 60% by weight. Approximately two-thirds of this water resides in the macropores and larger mesopores, which can be removed by air drying, leaving 15% to 20% sorbed water after the air drying process. Many other biomasses have water in the macropores that can be easily removed by air drying. It is preferable to remove as much water as possible by sun drying, air drying, or a combination of both. The more strongly sorbed water remaining after sun drying or air drying of different biomasses is generally in the range of 7% to 25% by weight. Generally, to meet biolandfill dryness specifications, it is preferred to use thermal drying techniques to remove some of the more strongly sorbed water.Thermal drying methods include heated shed dryers, belt dryers, tunnel dryers, trough dryers, conveyor dryers, rotary drum dryers, screw conveyor dryers, hearth dryers, moving bed dryers, and fluidized bed dryers. Thermal drying techniques can reduce moisture content to less than 1% by weight, but require capital and energy investments. Therefore, for any thermal drying process, there is an optimization between the cost of thermal drying (capital and operating costs) and the amount of water sorbed into the dried product. Reducing the amount of water in the sorbed product provides a safety margin below the level at which degradation occurs. In preferred embodiments, optimization of the sun drying, air drying, and / or thermal drying process produces biomass products with moisture contents of 1% to 20% by weight, preferably 2% to 15% by weight, and more preferably 3% to 10% by weight. Additionally, it may be preferable to chop the biomass into smaller pieces before drying. Chopping into pieces ranging in size from millimeters to several centimeters can facilitate handling and drying. A preferred method for drying chopped biomass is with a rotary dryer, which preferably produces a product with 2% to 10% water by weight in the biomass, which corresponds to a life-sustaining water activity (or dryness level) for most biomass isotherms.

[0028] To improve the economic viability of biolandfills, it is preferable to locate biolandfills within 5–200 miles of agricultural or forestry sites and sequester 10–100,000 kilotons of dry biomass per year in each biolandfill. This highly distributed sequestration saves the cost of transporting biomass long distances. It is also envisioned that any processing, such as drying, torrefaction, carbonization, anaerobic digestion, or liquid biofuel production, can be co-located with the biolandfill. These distributed biolandfills should be constructed to occupy a small fraction of the land area used for crop production. To minimize the biolandfill footprint, stored biomass should be compressed. Compaction has the added benefit of improving the biolandfill's mechanical stability, minimizing the volume that can hold free water, and improving economic viability. Furthermore, compaction limits the mass transfer of water and water vapor to the biomass, slowing its decomposition rate. The metric for compaction is the bulk density of the biomass, which excludes mass contributions from foreign materials, such as soil, earth, or plastic, that may be intentionally placed in the biolandfill. In a preferred embodiment, the bulk density of the compressed biomass components in the dry tomb is greater than 0.2 g / cc. In a more preferred embodiment, the bulk density of the compressed biomass components in the dry tomb is greater than 0.5 g / cc. In an even more preferred embodiment, the bulk density of the compressed biomass components in the dry tomb is greater than 0.75 g / cc. In a most preferred embodiment, the bulk density of the compressed biomass components in the dry tomb is greater than 1.0 g / cc. By comparison, uncompacted biomass has a bulk density in the range of approximately 0.02 to 0.15 g / cc. With biomass compression in the range of 0.7 to 1.4 g / cc, a 100-foot vertical height of the dry tomb structure can store approximately 86,000 to 170,000 metric tons of biomass per acre. If harvested energy crops or wood are sequestered in the dry tomb structure, this requires approximately 0.005% to 0.01% of the land area used for agriculture or forestry annually.

[0029] Compacted biomass can be in the form of compacted bales or briquettes (bricks, sheets, pellets, or extrusions) that are dumped into the biolandfill, or the biomass can be dumped into the biolandfill and compacted in situ. When compacting biomass in situ, it is preferable to dump a 0.1- to 4-meter-thick layer of biomass into a section of the landfill, compact the layer, and repeat this process multiple times to produce a compacted fill. Methods used to compact biomass in situ include soil compaction techniques such as dynamic compaction, vibrocompaction, and quasi-static compaction. Dynamic compaction is a ground improvement technique that densifies soil and fill material by using drop weights. Weights typically range from 6 to 30 tons (up to 40 tons), and drop heights typically range from 10 to 30 meters (30 to 100 feet), sometimes even exceeding that. Vibrocompaction repeatedly and rapidly applies stress to the soil or fill material via mechanically driven plates or hammers. This is often combined with quasi-static compaction methods such as rolling compaction. Quasi-static compaction techniques, commonly used in public landfills, apply stress to soil or fill material at low speeds by rolling a heavy cylinder across the surface or by the kneading action of a device such as a "sheep's foot" roller. For all methods used to compact biomass in situ, it is preferable to perform multiple passes of compaction equipment over the exposed surface in a manner similar to that used in compacting soil and municipal waste. The density of the compacted bale is typically lower than that produced by dynamic compaction, vibration compaction, and quasi-static compaction. Baling machines are commonly used in agricultural production to compress biomass into blocks (bales) secured in place with plastic wrap or wire straps. The bulk density of compacted agricultural bales varies depending on the type of machine used and can range from approximately 0.15 g / cc to 0.35 g / cc. Higher density compaction can be achieved using reciprocating ram / piston presses, screw presses, roll presses, and extruders that produce briquettes in the form of bricks, sheets, pellets, or extrudates.This type of machine can generate compaction pressures of 5,000 psi to 50,000 psi, resulting in compressed biomass briquettes with bulk densities ranging from 0.5 to 1.5 g / cc. For example, measured compaction curves for small-grained miscanthus and switchgrass require pressures ranging from 10,000 psi to 35,000 psi to achieve briquette densities ranging from 0.6 g / cc to 1.1 g / cc. In a preferred embodiment, briquettes in the form of compressed biomass bricks, sheets, pellets, or extrudates are stacked in bundles and placed in plastic bags or wrapped in plastic. The purpose of the bags or wraps is to aid in handling the compressed biomass and to help keep the biomass dry during construction of the biolandfill. Therefore, in a preferred embodiment, the plastic bags or wrapping are sealed to prevent liquid water from entering the enclosed biomass. The sealed plastic bags or wrapping form either a secondary or tertiary barrier to water transport. In the absence of a secondary water transport barrier, such as a sealed plastic sheet, a sealed plastic bag or sealed plastic wrapping forms a secondary water transport barrier. In the presence of a secondary water transport barrier, such as a sealed plastic sheet, a sealed plastic bag or sealed plastic wrapping forms a tertiary water transport barrier. The sealed plastic bag or plastic wrapping provides resistance to water vapor mass transfer and resists mechanical tearing or puncture. Plastic resins that can be molded into bags or sheets that meet these requirements include low-density polyethylene, linear low-density polyethylene, metallocene-catalyzed polyethylene resins, high-density polyethylene, polypropylene, and resin blends of these materials. The preferred thickness of the bag or sheet is determined by mechanical and economic considerations and ranges from 1 mil to 20 mils, preferably 2 mils to 8 mils. Sealing to prevent moisture ingress is accomplished by either adhesive or a thermal sealing process, such as heat sealing or plastic welding.The mass of compressed biomass briquettes (bricks, sheets, pellets, or extrusions) enclosed in bags or plastic wrapping can range from 10 to 2,000 pounds, more preferably from 20 to 500 pounds, and even more preferably from 40 to 200 pounds. Heat-sealed trash bags, commonly used in sizes 5 to 100 gallons, provide examples of plastic bags that can be used to enclose and protect compressed biomass briquettes. Such biomass briquette-filled bags or plastic wrapping are available as commercial products sold to consumers to hold fuel for fireplaces.

[0030] There are various methods that can be used to construct biolandfills with the described compositions and characteristics. Construction techniques involve a wide variety of engineering and scientific practices, including construction engineering, environmental engineering, geotechnical engineering, materials science and engineering, site development and planning, structural engineering, surveying, water resources engineering, chemical and process engineering, analytical chemistry, botany, agronomy, biology, and civil systems engineering. All of these disciplines are necessary to construct the described biolandfill compositions and characteristics. From a description of a biolandfill's composition and properties, those skilled in the relevant scientific and engineering techniques can devise a wide variety of construction methods, so only a brief, high-level description touching on a few of the myriad possible construction methods will be presented. Methods used to construct biolandfills with bases above or near the ground surface differ from construction methods with bases far below the ground surface. Biolandfill construction begins with preparing the surface onto which the bottom water transport barrier(s) will be installed. If the biolandfill is below ground surface, this involves excavating an open-air structure, while for surface construction, this primarily involves grading the land surface. Provisions are also made to drain stormwater from excavated or leveled structures and from biolandfills when filled. Sloping the newly exposed soil surface and draining to a spot where the water can be pumped or directed to a location where it can be disposed of are just a few examples of such provisions. Others are diverters, gutters, plastic sheeting, or tarp systems designed to direct stormwater away from the biomass during construction of the dry tomb structure. Various types of diverters or gutters are used throughout construction and can be made from earthen structures, plastic, tarps, or sandbags.

[0031] In a preferred embodiment, a high-capacity sorbent is used during construction to prevent rainwater or dew from seeping into the biomass composite being filled. The high-capacity sorbent is used to form a temporary barrier to reduce the effects of rain or dew, or as part of a flow-through barrier. In the most preferred embodiment, the high-capacity sorbent is renewable. The sorbent can be spread on the exposed surface of the biomass and mechanically collected before more biomass is added. Alternatively, it can be placed in a water-permeable bag, such as a burlap bag, which is placed on top of the biomass to prevent water intrusion and incorporated before adding more biomass. Alternatively, it can be composited with geotextile, which is placed on the exposed surface of the biomass and incorporated before adding more biomass. In another embodiment, the material is placed in areas adjacent to a tarp, temporary geomembrane, or other covering material to prevent water intrusion through gaps, overlaps, or seams. In this embodiment, it can be placed either above or below gaps, overlaps, or seams in the tarp, temporary geomembrane, or other covering material. In all examples, the high-capacity sorbent blocks the flow of liquid water through gaps, overlaps, or seams into the dry biomass during filling. In all cases, economic considerations favor the use of renewable, high-capacity adsorbents that can be reused during construction. To reuse the high-capacity adsorbents, they are regenerated thermally, by exposure to dry air, or by exposure to wind and solar radiation outdoors. A high-capacity, renewable adsorbent for this application must have a working capacity of at least 0.5 grams of water per gram of dry sorbent. An example of a renewable, high-capacity adsorbent is a highly adsorbent polymer capable of adsorbing 50 to 400 times its dry weight in water when exposed to fresh water. An example of a highly adsorbent polymer is sodium polyacrylate. Other examples are crosslinked polyacrylates and polyacrylamides; cellulose- or starch-acrylonitrile graft copolymers; and crosslinked maleic anhydride copolymers.

[0032] To construct the biolandfill, the land surface is excavated and leveled. Next, construction of the bottom seal protective layer begins on what will become the bottom of the dry tomb structure. Once the protective layer is in place, construction of the bottom seal begins with the installation of at least one water transport barrier. Additional water transport barriers may be installed at this point, along with any optional protective and spacer structures that will become part of the bottom seal. Following this step, biomass can be added to the biolandfill. It is envisioned that the biomass will be stored at or near the biolandfill site. Ideally, storage occurs in relatively dry conditions, such as under a tarp or in a warehouse or shed, and, if necessary, is dried and optionally chopped before being added to the biolandfill under construction. The method by which it is added depends largely on how the biomass was compressed. If it is compressed using equipment that cuts, dries, and produces biomass briquettes (which may be plastic-wrapped or bagged), it can be physically stacked within the biolandfill. Similarly, compressed, dry bales of biomass, optionally plastic-wrapped, can be physically stacked within the biolandfill. When compressed biomass is stacked as briquettes or bales, earthworks may be constructed to secure them, provide anchoring points for temporary tarp systems, provide stormwater drainage, or provide a base for a temporary canopy structure used to protect the fill area from rain. Potentially, these earthworks could account for 25% of the volume of the completed dry tomb structure, increasing as the height of the stacked biomass increases. One form of earthwork structure is a dike structure or causeway that forms a channel in which the compressed biomass is stacked. Additionally, these earthworks can be used to compartmentalize areas of biolandfill with sealed plastic sheeting, which acts as a secondary water transport barrier. If a secondary water transport barrier is installed, optional plastic wrapping or bagging of the compressed biomass provides a tertiary water transport barrier.In the absence of plastic sheeting compartmentalization, plastic wrapping or bagging of the compressed biomass provides a secondary water transport barrier.

[0033] For mechanical compaction, biomass may be included in a portion of the biolandfill, and densified by multiple passes through a mechanical compactor. In some cases, the biomass is shredded before dumping. Construction using this type of compaction can be done with or without earthworks. A temporary tarp system and / or canopy can be constructed to keep the biomass dry. Additionally, plastic sheeting can be installed to seal the fully compacted area. Such sealing plastic sheeting compartmentalizes the biolandfill and provides a secondary water transport barrier. In all cases, the biolandfill is built gradually from the base up, and as it rises, desired piping structures can be constructed or installed later, for example, by drilling. Once it rises from above ground level to its filled height, the top seal is completed. This involves the installation of at least one water transport barrier and any spacer structures, or additional water transport barriers, or additional layers used to protect the top seal. The completed water transport barrier is covered when the water transport barrier is constructed using soil, or after the tomb construction is complete. Sealable piping rising above the finished biolandfill surface can be terminated with valves and provisions for connection to analytical equipment. Provisions can also be made to allow for purge gas flow for a verifiable and repairable biolandfill design.

[0034] Biomass sequestration using the biolandfill compositions described herein can be used as a means to obtain CO2 offset credits. Such credits can be issued by private companies, charities, charitable trusts, governments, or quasi-governmental organizations. The credits can be in the form of payments, some form of compensation, or tax credits. The credits are based on the amount of biomass sequestered or the amount of biomass sequestered in the future. The value of the credit for the sequestered biomass can be based on a value assigned to the amount of carbon in the biomass, the amount of CO2 offset by the sequestered biomass, or simply the amount of biomass sequestered. Credits can be paid immediately or over a period of time. Credits may have provisions based on sequestration performance and verification of sequestration performance. The scope of the present invention includes any credits issued for sequestration of biomass in a verifiable dry tomb biolandfill, where the verifiable dry tomb biolandfill includes: a. a biomass surrounded by top and bottom seals containing at least one barrier to water transport forming a dry tomb structure; b. a soil-containing cover layer that serves to protect the enclosed biomass from atmospheric disturbances; c. One or more accessible, sealable, true-wall pipes or conduits connected to the enclosed biomass; d. A means of monitoring biomass decomposition of enclosed biomass.

[0035] The following examples illustrate aspects of the present invention.

[0036] Example 1: This example illustrates a simple form of verifiable and modifiable biolandfill. A cross-section showing the components of a verifiable and remediable biolandfill is shown in Figure 1. It is a dry storage biolandfill containing dry biomass [1] formed by top and bottom seals containing a single barrier to water transport [2] surrounding the dry biomass-containing area, two coaxial, sealable solid-walled pipes (or conduits) [4, 9] connecting the biolandfill surface to the interior of the dry tomb, and an atmospheric isolation valve [5, 8] that can be opened to sample gas components or purge with gas. The top and bottom seals, including the water transport barrier [2], define the boundaries of the dry tomb. The dry tomb structure is constructed on the earth's surface

[10] but is subsurface because it is covered with a thick layer of soil [3] that protects it from environmental disturbances. In other potential embodiments, the earth's surface

[10] is excavated, and the base of the dry tomb structure is located below the Earth's surface at a depth similar to that of a public landfill or mining operation. Features [1, 2, 3, 4, 5, 8, and 9] comprise the elements of a verifiable and repairable dry tomb biolandfill capable of isolating biomass. Additionally, a hermetic seal must be present to prevent water leakage through the water transport barrier. In this embodiment, there is only one hermetic seal [6], as one sealable pipe (or conduit) [9] runs coaxially inside the other [4]. Embodiments 3 and 6 identify a non-coaxial piping arrangement that provides the essential elements of a verifiable and repairable dry tomb biolandfill capable of isolating biomass. In this embodiment, a smaller diameter sealable pipe [9] is coaxially sealed to a larger diameter sealable pipe [4], which mechanically supports the coaxial piping and prevents atmospheric moisture from entering the coaxial piping structure [7]. As shown in the figure, a second, smaller diameter sealable pipe [9] extends to approximately the base

[12] of the dry tomb structure. This smaller diameter sealable pipe [9] has a valve [8] that seals the pipe from the atmosphere.This valve [8], when opened, can be used in conjunction with a valve [5] on a larger diameter sealable pipe [4] to allow purge and sample gas to flow from the biolandfill, or simply to purge water and moisture from the biolandfill, or to address unexpected biogas generation. Depending on preference, the purge can flow from the top of the dry tomb to the bottom, or from the bottom to the top of the dry tomb. Note that such a purge is not a feature of public landfills. Furthermore, the base

[11] of the dry tomb structure is preferably sloped to drain water to a spot where it can be collected. As shown, the spot

[12] from which the water drains is near the lateral midpoint of the biolandfill. By modifying the grading, this spot

[12] can be moved laterally anywhere across the base of the biolandfill. It is also possible to excavate a depression at this spot, providing the option to accumulate larger volumes of water. Also, note that Figure 1 is a schematic diagram and is not to scale. In the embodiment shown in Figure 1, the lateral extent of the biomass near the bottom of the landfill ranges from 100 to 1,000 feet. The height of the biomass-containing area (approximately locations

[12] to [6]) is 30 to 400 feet. In this example, the water transport barrier [2] is made of a heat-welded sheet of polyethylene 80 to 160 mils thick. Optionally, a clay layer, geonet, geomembrane, geotextile, geocomposite, or combinations thereof may be placed on one or both sides of the polyethylene sheet to mechanically protect the water transport barrier [2]. This mechanical protection constitutes the top and bottom seals. In this embodiment, the larger sealable pipe [4] has a diameter of 4 to 8 inches, and the inner sealable pipe [9] has a diameter of 1 to 3 inches. Both sealable pipes [4, 9] have solid walls and are made of PVC plastic. The soil layer that covers and protects the top surface of a dry tomb structure [3] ranges in thickness from 20 to 60 feet.The isolated region [1] of the dry tomb structure has a biomass volume fraction of at least 40%, more preferably, this region [1] has a biomass volume fraction of greater than 60%, and most preferably, this region [1] has a biomass volume fraction of greater than 80%. Many other materials can be included in this region, including gas voids, soil, clay, and secondary or tertiary water transport barriers. This region [1] may also be compartmentalized with water transport barriers, soil structures, earthworks, or clay structures. In all cases, the biomass within this region [1] is compacted to a bulk density greater than 0.2 g / cc, and the dry tomb has an average water activity of less than 0.85.

[0037] The biolandfill described in this embodiment is verifiable and repairable. Verification can be performed by installing a pressure gauge on one side of the sealable pipe [4 or 9] connecting the interior of the dry tomb to the atmosphere. As long as the valves [5, 8] remain closed, the pressure in this sealable pipe [4 or 9] increases as the biomass decays. Monitoring the pressure gauge allows for assessment of biomass decomposition. More preferably, verification is performed using an analytical instrument connected to one side of the sealable pipe [4 or 9] to measure the composition of the gas vented from the purge flowing into the sealable pipe [9 or 4] on the other side of the open valves [5 and 8]. If significant biomass decomposition is detected, the biolandfill can be purged with dry gas to remove water. This type of dry purge provides a means of repairing the isolation conditions in the dry tomb biolandfill. When the biolandfill described in this example is constructed, it is not necessary to introduce (i.e., flow) purge gas into the biolandfill. In this case, the biolandfill is still verifiable because biomass decomposition can be measured by monitoring the increase in pressure due to biogas generation. Alternatively, if pressure increases, the gas components can be measured by flushing enough gas from the dry tomb to obtain a representative gas sample. Thus, the biolandfill as constructed is an example of a "verifiable dry tomb biolandfill for biological carbon sequestration." Once a device for flushing purge gas is added, the biolandfill becomes a "verifiable and remediable dry tomb biolandfill for biological carbon sequestration."

[0038] Without the coaxial pipe [9], there would be only one pipe [4] running from the Earth's surface to the interior of the dry tomb structure. This makes the biolandfill formed from elements [1, 2, 3, 4, 5, 6, 10, 11, and 12] (without the second pipe) an example of a "verifiable dry tomb biolandfill for biological carbon sequestration."

[0039] Example 2: Example 2 relates to improvements to the top and bottom seal structure utilized in Example 1, and a cross-section of the improved biolandfill is shown in Figure 2. This example has top and bottom seals containing two water transport barriers [22, 34], while Example 1 has only one water transport barrier [2]. Figure 2 shows a cross-section of a dry tomb structure [22, 33, 34] containing dry biomass. There are two barriers to water transport [22, 34] surrounding the area containing dry biomass

[21] . In addition, there are two sealable solid-walled pipes (or conduits) [24, 29] connecting the surface of the biolandfill to the interior of the dry tomb, and atmospheric isolation valves [25, 28] that can be opened when sampling gas components or purging with gas. The water transport barriers [22, 34] are nested with a spacer structure (or layer)

[33] that separates them. The spacer structure (or layer)

[33] can include soil, compacted soil, clay, geosynthetic clay, geotextile, geonet, geosynthetic fabric, high-capacity sorbent, and combinations thereof. This layer serves to mitigate defects in the outer water transport barrier

[22] . The thickness of this separation layer (or spacer structure)

[33] ranges from 0.05 to 1 meter. In some additional embodiments, the composition of the separation layer (or spacer structure) can be different at the top, bottom, and sides of the biolandfill. In some additional embodiments, the top and bottom seals have additional layers to mechanically protect them from ground disturbances or provide additional protection against water intrusion (such as a clay layer or a geonet that drains water from the biolandfill). In some embodiments, the top and bottom seals have another layer(s) inside the internal transport barrier

[34] to provide mechanical protection from mechanical disturbances from machinery used to place biomass in the landfill or to provide additional protection from water ingress (such as a clay layer). Nested water transport barriers [22, 24] and spacer structures

[33] form the top and bottom seals of the biolandfill. These seals define the boundaries of the dry tomb structure.

[0040] A top- and bottom-sealed dual water transport barrier structure [22, 33, 34] requires a sealable pipe

[24] running from the interior of the dry tomb structure to the surface and two water seals [26, 35] between the water transport barriers [22, 34]. In a different embodiment, the sealable pipe

[24] is sealed to only one of the water transport barriers. Other aspects of this embodiment are similar to the embodiment shown in Figure 1. The base

[31] of the dry tomb structure is sloped to drain to a water collection spot

[32] . Running coaxially inside the sealable pipe

[24] is a second, smaller-diameter sealable pipe

[29] that connects the interior of the dry tomb through the water transport barrier to the surface of the biolandfill. This smaller-diameter sealable pipe

[29] is coaxially sealed to a larger-diameter sealable pipe

[24] that provides mechanical support for the coaxial piping and prevents atmospheric moisture from entering the coaxial piping structure.

[27] A second, smaller diameter sealable pipe

[29] extends to approximately the base

[32] of the dry tomb structure. This smaller diameter sealable pipe

[29] also has a valve

[28] that seals the pipe from the atmosphere. When opened, this valve

[28] can be used in conjunction with the valve

[25] on the larger diameter sealable pipe

[24] to flow purge and sample gas from the biolandfill, or simply to purge water and moisture from the biolandfill, or to deal with unexpected amounts of biogas generation. Depending on preference, the purge can flow from the top of the dry tomb to the bottom, or from the bottom to the top of the dry tomb. The base of the biolandfill is slightly above the Earth's surface

[30] and is protected from the Earth's environment by a thick layer of soil

[33] . Similarly, Figures 1 and 2 are schematic and not to scale.

[0041] This embodiment provides another example of a verifiable and repairable biolandfill for biological carbon sequestration. When the biolandfill described in this example is constructed, a means for introducing (i.e., flowing) purge gas into the biolandfill is not necessarily required. In this case, the biolandfill is still verifiable because biomass decomposition can be measured by monitoring the increase in pressure due to biogas generation. Alternatively, if pressure increases, gas components can be measured by allowing enough gas to flow from the dry tomb to obtain a representative gas sample. Thus, the as-constructed biolandfill is an example of a verifiable dry tomb biolandfill for biological carbon sequestration. With the addition of a device for flowing purge gas, the biolandfill becomes a verifiable and repairable dry tomb biolandfill for biological carbon sequestration.

[0042] Without the coaxial pipe

[29] , there would be only one pipe

[24] running from the Earth's surface to the interior of the dry tomb structure. This makes the biolandfill formed from elements [21, 22, 23, 24, 25, 26, 30, 31, 32, 33, 34, and 36] (without the second pipe) an example of a verifiable dry tomb biolandfill for biological carbon sequestration.

[0043] Example 3: A cross section of this embodiment, showing different methods of purging (flowing gas) through the biolandfill, is illustrated in Figure 3. In Example 2 (illustrated in Figure 2), the purge gas would flow vertically (top to bottom or bottom to top). In this embodiment, the purge flows primarily horizontally between two grooved (or porous) pipes [55, 56]. These pipes are mechanically joined to two sealable solid-walled pipes [44, 46] that run from the interior of the dry tomb to the surface. The top and bottom seal structures in this example are similar to those in Example 2, including nested water transport barriers [42, 54] and a spacer structure

[53] , and the top and bottom seals define the boundaries of the dry tomb. Sealable solid-walled pipes [44, 46] are hermetically sealed [48, 49, 58, 59] to both the inner

[54] and outer

[42] water transport barriers to prevent water intrusion into the dry tomb structure [42, 53, 54] containing the dry biomass

[41] . In another embodiment, the pipe is sealed to only one of the water transport barriers. To purge the biolandfill, a relatively dry gas, such as low-humidity air, is injected by opening valves [45, 47] that seal the solid-walled pipes [44, 46]; the gas is injected into one side of the solid-walled pipe and exits the other. Within the dry tomb, grooved (or porous) piping [55, 56] mechanically connected to the sealable solid-walled pipes [44, 46] injects and collects gas from the area containing the biomass

[41] . The gas flows primarily horizontally and can be used to sample gas components from the bulk of the dry tomb, purge excess water vapor, purge unwanted amounts of biogas, or control the degree of anoxic and anaerobic conditions within the dry tomb. By studying the time dependence of the effluent composition, an approximate map of the gas components within the dry tomb can be constructed. The base of the dry tomb structure is not sloped as shown in Figure 2, although it is possible to implement this embodiment with a sloped base. In most other respects, the structure of the biolandfill is similar to that shown in Figure 2 (Example 2). The dry tomb is constructed on the surface

[50] and covered with a layer of soil

[43] .Low water activity within the biolandfill is maintained using top and bottom seals containing double water barriers [42, 54] separated by a spacer structure

[53] . Again, please note that Figure 3 is a schematic diagram and not to scale, and that this is an example of a verifiable, repairable, and conservative biolandfill for biological carbon sequestration. When the biolandfill described in this example is constructed, a means for introducing (i.e., flowing) purge gas into the biolandfill is not necessarily required. In this case, the biolandfill is still verifiable because biomass decomposition can be measured by monitoring the increase in pressure due to biogas generation. Alternatively, if pressure increases, gas components can be measured by flowing enough gas from the dry tomb to obtain a representative gas sample. Thus, the as-constructed biolandfill is an example of a verifiable, dry-tomb biolandfill for biological carbon sequestration. With the addition of a device for flowing purge gas, the biolandfill becomes a verifiable, repairable, and conservative dry-tomb biolandfill for biological carbon sequestration.

[0044] Without the secondary plumbing [46, 55], there is only one plumbing [44, 55] running from the Earth's surface to the interior of the dry tomb. This makes the biolandfill formed from elements [41, 42, 43, 44, 45, 49, 50, 53, 54, 56, and 59] (without the secondary plumbing) an example of a verifiable dry tomb biolandfill for biological carbon sequestration.

[0045] Example 4: This embodiment is shown in Figure 4 and illustrates an alternative configuration of the upper seal structure containing dual water transport barriers separated by a spacer structure. A protective layer of thick soil

[63] with vegetation growing on the surface

[72] covers the layer

[78] protecting the outermost water transport barrier

[62] . The thickness of the soil layer

[63] ranges from 10 to 100 feet, and the first 3 feet (approximately 1 meter) above the layer

[78] protecting the outermost water transport barrier

[62] is substantially free of boulders and stones. In this embodiment, the layer

[78] protecting the outermost water transport barrier

[62] is a water-draining geonet. In other embodiments, it may be a clay layer, a synthetic clay layer, a geocomposite, a geotextile, a geomembrane, or other similar material. Additionally, the protective layer

[78] may be a combination of such protective materials. The outermost water transport barrier

[62] is made from a 40- to 160-mil-thick polyethylene sheet thermally bonded with welded seams to prevent hydraulic flow of groundwater. The outermost water transport barrier

[62] is separated from the innermost water transport barrier

[74] by a spacer structure consisting of three layers [75, 76, 77]. The upper and lower layers of the spacer structure [77, 75] are composed of layers of geosynthetic clay 0.05 to 1 ft thick, while the middle layer of the spacer structure

[76] is composed of a layer of compacted stone-free soil 0.1 to 2 ft thick. This is the simplest composition for the middle layer; a wide variety of other options exist, including those incorporating high-capacity sorbents into this layer

[76] . The spacer structure [75, 76, 77] mechanically protects the water transport barrier [62, 74] and also provides mass transport resistance to water ingress. Furthermore, water penetrating into the geosynthetic clay layers [75, 77] causes them to expand, helping to seal imperfections in the water transport barrier [62, 74]. There are many other possible embodiments of spacer structures [75, 76, 77], some with additional layers and others with fewer or different layers. An additional protective layer

[79] is located between the area containing the compacted buried biomass

[61] and the innermost water transport barrier

[74] . When incorporated into a biolandfill design, this layer can provide additional mechanical protection for the water transport barrier [62, 74] or additional mass transfer resistance against water intrusion.In this embodiment, it is a 0.2-1 ft thick layer of bentonite clay. Note that Figure 4 shows only the top layer of the biolandfill and the top portion of the biomass-containing area. In this embodiment, the upper seal structure [62, 74, 75, 76, 77, 78, 79] consists of the water transport barrier, spacer structure, and all mechanical protection layers.

[0046] Example 5: This example is shown in Figure 5 and illustrates an alternative embodiment of the configuration of a bottom seal structure [82, 94, 95, 96, 97, 98, 99] with double water transport barriers [82, 94] separated by spacer structures [95, 96, 97]. The biolandfill is constructed using a leveled or excavated surface

[91] from the ground

[90] . A layer of compacted, stone-free soil

[92] is installed on the leveled or excavated surface

[91] above the base of the biolandfill

[89] . This provides some protection to the bottom seal structure [82, 94, 95, 96, 97, 98, 99]. The bottom of the bottom seal structure has a protective layer

[99] , which in this embodiment is a 1-4 mm thick geotextile. A wide variety of other protective layers can be used, including layers of bentonite clay, geocomposite, geotextile, or geonet. Alternative embodiments do not include these protective layers, and other embodiments have additional protective layers. What becomes the outermost water transport barrier

[82] is installed on top of the top protective layer

[99] . This water transport barrier

[82] , along with the inner water transport barrier

[94] , is made from 40-160 mil thick polyethylene sheets thermally bonded with welded seams to prevent hydraulic flow of groundwater. A three-layer spacer structure [95, 96, 97] is installed on top of the outermost water transport barrier

[82] . The top and bottom layers of the spacer structure [97, 95] are composed of layers of geosynthetic clay 0.05-1 ft thick, and the middle layer of the spacer structure

[96] is composed of a layer of compacted stone-free soil 0.1-2 ft thick. This is the simplest composition of the middle layer; there are a wide variety of other options, including those incorporating a high-capacity sorbent into this layer

[96] . Similar to Example 4, the spacer structure [95, 96, 97] mechanically protects the water transport barrier [82, 94] and also provides mass transport resistance to water ingress. The clay layers [95, 97] repair water transport defects by expanding and blocking hydraulic flow. Other possible embodiments of the spacer structure [95, 96, 97] may have additional layers, and other embodiments may have fewer or different layers.On top of the spacer structure, an inner water transport barrier

[94] is installed and covered with a layer

[98] that protects it from the machinery used to form the area containing the compressed biomass

[81] . In this embodiment, the protective layer

[98] is a geotextile, although a wide variety of other materials may be used. In this embodiment, the bottom sealing structure [82, 94, 95, 96, 97, 98, 99] is made up of the water transport barrier, the spacer structure, and all mechanical protective layers.

[0047] Example 6 This embodiment is shown in Figure 6, which illustrates elements of a verifiable and repairable dry tomb biolandfill constructed with a base

[0129] well below the ground surface

[0100] . The cross-section in Figure 6 shows a schematic (not to scale) of two water transport barriers [102, 106] separated by a spacer structure

[0113] that forms top and bottom seals [102, 106, 113]. These seals [102, 106, 113] define the boundary of the dry tomb structure, which contains an area with dry biomass

[0101] extending from well below to well above the ground surface. The base of the dry tomb structure can range from 20 to 80 feet below the ground surface, and the top of the dry tomb structure can range from 30 to 300 feet above the ground surface. The lateral extent of the dry tomb structure can range from 100 to 1,000 feet. The top of the biolandfill extends 20–100 ft above the dry tomb structure, where a thick layer of soil

[0103] is installed to protect the dry tomb structure [102, 106, 113]. Six solid-walled sealable pipes [124, 104, 109, 114, 120, 134] extend from the surface into the dry tomb structure. All have valves [125, 105, 108, 115, 118, 135] that allow for the flow of purge gas and / or gas sampling. To prevent groundwater intrusion, the solid-walled sealable pipes [124, 104, 114, and 134] are hermetically sealed to the outer water transport barrier

[0102] [228, 208, 218, 238]. Furthermore, these pipes [124, 104, 114, 134, and 134] are hermetically sealed [226, 206, 216, 236] to the inner water vapor transport barrier

[0106] . In an alternative embodiment, these solid-walled sealable pipes [124, 104, 114, and 134] are hermetically sealed to only one of the water transport barriers. One of the sealable pipes

[0109] is coaxially positioned inside another sealable pipe

[0104] and runs to approximately the base

[0129] of the dry tomb structure, which is sloped to collect any unexpected (unwanted) liquid water that drains to the base. It is supported and sealed to the sealable pipe

[0104] by a flange

[0107] .The sealable pipe

[0109] , which runs almost to the base of the dry tomb structure

[0129] , has an inner diameter ranging from 2 to 8 inches and allows a pump to be inserted downhole, if necessary, to bring any potential unexpected (unwanted) water accumulation to the surface. The valve

[0108] installed on this pipe

[0109] is either removable or has clearance when opened, allowing the pump to be inserted downhole. A wide variety of downhole pumps are available, and many are used in oil and gas wells. Furthermore, these coaxially routed pipes [109, 104] can be used to flow gas primarily vertically through a portion of the dry tomb structure. Figure 6 shows another coaxial piping arrangement [120, 114]. A flange

[0117] seals the inner pipe

[0120] to the outer pipe and serves to support the inner pipe and the porous pipe

[0119] to which the solid-walled sealable pipe

[0120] joins the interior of the dry tomb structure. This porous pipe

[0119] can be used to distribute purge gas throughout most of the height of the dry tomb structure. Towards the perimeter of the landfill, two additional solid-walled sealable pipes [124, 134] are surfaced. Both of these solid-walled sealable pipes [124, 134] are joined to grooved pipes [229, 239] within the dry tomb structure. These grooved pipes can be used to distribute purge gas from near the perimeter of the dry tomb structure. Used in combination, the solid-walled sealable piping [124, 104, 109, 114, 120, 134] can be used at the surface to purge and sample gas from most of the volume of the dry tomb structure.

[0048] If significant biomass decomposition is detected, there are several ways to purge the dry tomb structure with dry gas to remove water and / or pump liquid water out of the dry tomb. These types of water vapor and liquid water removal provide a means to repair the sequestration conditions in the biolandfill. When the biolandfill described in this example is constructed, a means to introduce (i.e., flow) purge gas into the biolandfill is not necessarily required. In this case, the biolandfill is still verifiable because biomass decomposition can be measured by monitoring the increase in pressure due to biogas generation. Alternatively, if pressure increases, gas components can be measured by flowing enough gas from the dry tomb to obtain a representative gas sample. Thus, the as-constructed biolandfill serves as an example of a verifiable dry tomb biolandfill for biological carbon sequestration. With the addition of a device to flow purge gas, the biolandfill becomes a verifiable and repairable dry tomb biolandfill for biological carbon sequestration.

[0049] Example 7 This example illustrates a method for quantitatively predicting water activity within a biomass-filled dry tomb structure and provides a method for determining how dry the biomass needs to be before being filled into the dry tomb structure.

[0050] Biomass acts as a water adsorbent, and exemplary isotherms are shown in Figure 7. The isotherms in Figure 7 show HO uptake at 25°C in various biomasses as the water activity increases in units of: Weight fraction of sorbed HO = mass of sorbed HO / {mass of sorbed HO + mass of dry biomass}) Equation 3

[0051] This type of isotherm is often called an adsorption branch isotherm and is slightly different from a desorption branch isotherm, which is measured as the water activity decreases. Adsorption isotherms for Miscanthus sinensis (a highly productive energy crop) are shown over the full range of water activity.w <0.02), water loading increases sharply as water populates the strongly bound sites. w ), the amount of sorbed water gradually increases from about 5% to about 20% by weight. w At pH >0.85, the water loading rises much more rapidly due to the filling of mesopores and macropores in Miscanthus. Figure 7 also shows water sorption isotherms covering the region of interest for long-term sequestration of prairie cordgrass and hardwoods. The hardwood isotherm is an average of 10 different hardwood species (red oak, white oak, yellow poplar, sweet bay, white ash, green ash, and American elm). In the region of interest for water activity for biomass storage, the isotherms are seen to be qualitatively similar to Miscanthus. This qualitative similarity partially extends to most other forms of biomass, since the isotherms in this region are set by the adsorption of water into mesopores and some macropores. The thermodynamics of adsorption into mesopores and micropores have a moderate temperature dependence, and Figure 8 shows this for Miscanthus water sorption isotherms at 20°C, 25°C, and 40°C. Most of the difference between them is due to the low water activity (a w The temperature dependence of the isotherm at temperatures <0.02 (Fig. 1) is due to the strongly adsorbed water content, which dominates the shape of the isotherm. Therefore, a limited number of isotherms can quantitatively estimate the required level of biomass drying.

[0052] To illustrate this, consider the drying requirements for sequestration of Miscanthus as an exemplary case. The amount of water ultimately contained in sequestrated Miscanthus within a biolandfill is the sum of the amount of water accumulated from precipitation and the amount of water introduced when the dried biomass (Miscanthus) is placed in the biolandfill. Using this fact, along with the graph shown in Figure 7, we can calculate the relationship between the allowable water fraction in the dried biomass placed in the dry tomb and the grams (or tons) of rainwater incorporated during construction per gram (or ton) of completely dried biomass for water activities of 0.85, 0.75, and 0.6. This relationship is graphically depicted in Figure 9, where the drying requirements to achieve water activities of 0.85, 0.75, and 0.6 are shown. The vertical axis is the dimensionless ratio of the mass of water in the dried biomass placed in the dry tomb to the weight of the completely dried Miscanthus placed in the dry tomb. This mass ratio of water in the dry biomass to the completely dried miscanthus is called the water weight fraction in the dry biomass (or miscanthus), sometimes expressed as a weight percent. The horizontal axis is the dimensionless ratio of the mass of rainwater incorporated during construction to the weight of the completely dried miscanthus in the dry tomb. This is called the weight fraction of rainwater incorporated in the completely dried biomass (or miscanthus), sometimes expressed as a weight percent. Examination of Figure 9 reveals that if the miscanthus is dried until the water weight fraction in the dry biomass is 0.12 (or 12 wt%) and the fraction of rainwater incorporated in the completely dried biomass averages 0.093 (or 9.3 wt%), a water activity of 0.85 is achieved. To illustrate what this means, consider the amount of rainwater that must be uniformly distributed throughout the dry tomb to achieve 9.3 wt%. For a dry tomb structure with an average thickness of 100 feet containing miscanthus compacted to a bulk density of 0.85 g / cc, this equates to a 94-inch rainfall load being uniformly incorporated across the entire surface of the filled dry tomb. This is a very high rainfall load, and with protection from a tarp or other temporary water barrier, less than 2 inches of incorporation is expected.If miscanthus is dried until the weight fraction of water in the dried biomass is 0.12 (or 12 wt%), and the fraction of rainwater incorporated into the completely dried biomass averages 0.045 (or 4.5 wt%), a water activity of 0.75 is achieved. For the same dry tomb structure, averaging 100 feet thick and containing miscanthus compressed to a bulk density of 0.85 g / cc, this corresponds to 46 inches of rainfall being uniformly incorporated across the entire surface of the filled dry tomb. If miscanthus is dried until the weight fraction of water in the dried biomass is 0.12 (or 12 wt%), and the fraction of rainwater incorporated into the completely dried biomass averages 0.009 (or 0.9 wt%), a water activity of 0.6 is achieved. For the same dry tomb structure, averaging 100 feet thick and containing miscanthus compressed to a bulk density of 0.85 g / cc, this corresponds to 9.2 inches of rainfall being uniformly incorporated across the entire surface of the filled dry tomb. If the biomass in the dry tomb were 50 feet thick instead of 100 feet, the maximum amount of precipitation that could be uniformly incorporated into miscanthus dried to a moisture content of 12% by weight would be 47 inches for a water activity of 0.85, or 23 inches for a water activity of 0.75, or 4.6 inches for a water activity of 0.6. These examples provide a method for scaling to other dry tomb thicknesses, such as 25 feet and 150 feet.

[0053] Figure 9 also shows that if miscanthus is dried until the water weight fraction in the dried biomass is 0.08 (or 8 wt%) and the fraction of rainwater incorporated into the completely dried biomass averages 0.13 (or 13 wt%), a water activity of 0.85 is achieved. For a 100-foot-thick dry tomb structure containing miscanthus compressed to a bulk density of 0.85 g / cc, this corresponds to 132 inches of rainfall being uniformly incorporated across the entire surface of the filled dry tomb. If miscanthus is dried until the water weight fraction in the dried biomass is 0.08 (or 8 wt%) and the fraction of rainwater incorporated into the completely dried biomass averages 0.085 (or 8.5 wt%), a water activity of 0.75 is achieved. For the same 100-foot-thick dry tomb structure containing miscanthus compressed to a bulk density of 0.85 g / cc, this corresponds to 86 inches of rainfall being uniformly incorporated across the entire surface of the filled dry tomb. If the miscanthus is dried until the water weight fraction in the dry biomass is 0.08 (or 8 wt%), and the fraction of rainwater incorporated into the completely dried biomass averages 0.048 (or 4.8 wt%), a water activity of 0.6 is achieved. For the same dry tomb structure with an average thickness of 100 feet containing miscanthus compressed to a bulk density of 0.85 g / cc, this corresponds to 49 inches of rainfall being incorporated uniformly across the entire surface of the filled dry tomb. These results can also be scaled to other dry tomb thicknesses, such as 25 feet and 150 feet.

[0054] Example 8 This example discusses a preferred method for excluding rainfall during construction of a dry tomb biolandfill and achieving a water activity of less than 0.85 in the sequestered biomass. It describes the construction of a biolandfill design that is not directly verifiable, mitigable, or remediable. While this is the simplest design for a biolandfill, the described method applies to all verifiable, mitigable, or remediable biolandfills. This simplest biolandfill design includes a dry tomb structure formed by top and bottom seal structures containing at least one water transport barrier that encloses the compacted biomass. In this design, there is no piping structure extending from the dry tomb through the soil cover to the surface. During construction, it is very important to mitigate rainwater inflow to the biomass located within the area that will become the dry tomb. The dryness requirements in Example 7 are exemplified by the amount of rainwater that needs to be evenly distributed throughout the dry tomb. Storms are intermittent events, and therefore precipitation fluctuates dramatically. Although stormwater incorporated into biolandfills distributes evenly over time, biomass decomposition occurs as it is redistributed throughout the biomass filling the dry tomb structure. To mitigate this, it is preferred to limit the amount of stormwater incorporated into the biomass sequestered in the dry tomb structure to less than 2% by weight of the mass of the dried biomass, preferably less than 1% by weight of the mass of the dried biomass, more preferably less than 0.5% by weight of the mass of the dried biomass, and most preferably less than 0.2% by weight of the mass of the dried biomass. For a 100-foot-thick dry tomb structure filled with biomass compressed to an average bulk density of 0.85 g / cc, these weight percentages correspond to the uniform incorporation of 20 inches of precipitation across the surface of the filled dry tomb, 10 inches of precipitation across the surface of the filled dry tomb, 5 inches of precipitation across the surface of the filled dry tomb, and 2 inches of precipitation across the surface of the filled dry tomb.

[0055] Construction of a simple biolandfill design begins with the construction of a base and preparation of the surface onto which the bottom seal structure will be installed. Provisions are made to drain stormwater from the excavated or leveled structure and from the biolandfill when filled. Once a portion of the bottom seal is installed, the filling of dry biomass can begin. If the dry biomass is compacted and contained in plastic bags or plastic wrapping, it can be placed directly into the dry tomb. Otherwise, the dry biomass is spread across the constructed portion of the dry tomb and compacted using methods such as dynamic, vibration, and quasi-static compaction. The dynamic, vibration, and quasi-static compaction of the dry biomass spread across the portion of the dry tomb densifies the biomass and creates hydraulic resistance, thereby limiting the inflow of stormwater into the biomass. Hydraulic resistance is due, in part, to the closure of gaps and large pore structures in the spread biomass. If a storm with more than 0.5 inches of precipitation is forecast, biomass filling operations are suspended and stormwater mitigation procedures are completed before the precipitation event occurs. In a more preferred embodiment, if a storm with precipitation greater than 0.1 inches is forecast, biomass filling operations are suspended and stormwater mitigation procedures are completed before the precipitation event occurs. Once biomass filling operations are suspended, stormwater mitigation procedures are employed. In one embodiment, stormwater mitigation procedures deploy precipitation protection devices over exposed areas of the dry tomb structure under construction. This may involve the installation of temporary plastic sheeting or tarp systems, geomembranes, geotextiles, or canopies. In another embodiment, renewable high-capacity sorbent(s) are used to provide protection from stormwater. If the biomass is spread and compacted, precipitation mitigation procedures may involve excavating the wet biomass from the dry tomb structure being constructed after the storm has passed. Once excavated, the biomass may be dried outside the construction area. After the storm has passed and precipitation mitigation procedures have been completed, biomass filling operations can resume.

[0056] In a preferred embodiment, the biolandfill is covered on nights when significant condensation is expected. If the dry biomass is spread and compacted, the covering can be omitted and the wet biomass excavated from the top the following morning. This excavated wet biomass is allowed to dry outside the construction area.

[0057] In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrative embodiments are only examples of the invention and should not be construed as limiting the scope of the invention.

Claims

1. A verifiable dry tomb-type biolandfill, comprising: a. a biomass surrounded by top and bottom seals containing at least one barrier to water transport forming a dry tomb structure; b. a cover layer comprising soil that serves to protect the enclosed biomass from atmospheric disturbances; c. one or more accessible, sealable, true-wall pipes or conduits connected to said enclosed biomass; d. The verifiable dry tomb biolandfill, comprising a means for monitoring biomass decomposition of the enclosed biomass.

2. The composition of claim 1 , wherein the top and bottom seals comprise two or more nested water transport barriers.

3. The composition of claim 2 wherein there is a spacer structure between the nested water transport barriers.

4. The composition of claim 3 , wherein the spacer structure contains a high capacity adsorbent.

5. 10. The composition of claim 1, wherein the biomass is compressed to a bulk density of greater than about 0.2 grams per cubic centimeter.

6. 6. The method of claim 5, wherein the biomass is compressed using dynamic compression, or vibration compression, or quasi-static compression, or a combination thereof.

7. 10. The composition of claim 1, wherein the biomass has a moisture content ranging from about 2% to about 15% by weight.

8. 8. The composition of claim 7, wherein stormwater infiltration into the biomass isolated in the dry tomb structure is maintained at less than about 2% by weight of the mass of the completely dried biomass.

9. 10. The composition of claim 1, wherein the water activity of the gas in the dry tomb structure is less than 0.

85.

10. The barrier to water transport has a water activity in the range of about 0.9 to 1.0 on one side of the barrier being tested and 0.05 or less on the other side, measured at about 38°C, and about 0.00 to 0.5 g / m ２ 10. The composition of claim 1, wherein the composition provides a water vapor transmission rate in the range of 1000 psi / day.

11. The composition of claim 1 , wherein at least one secondary water transport barrier is present.

12. The composition of claim 11 , wherein at least one tertiary water barrier is present.

13. 10. The composition of claim 1, further comprising means for removing biogas produced in said enclosed biomass, said means for biogas removal comprising at least one of said sealable pipes or conduits.

14. 10. The composition of claim 1, comprising two or more sealable solid-walled pipes or conduits connected to the enclosed biomass and means for flowing a gas purge through the pipes or conduits, making the dry tomb biolandfill verifiable and repairable.

15. 15. The composition of claim 14, wherein means are provided for purging a portion of said dry tomb structure with flowing air having a relative humidity of less than about 60%.

16. 15. The composition of claim 14, wherein within said dry tomb at least one perforated or porous pipe or conduit is connected to at least one of said sealable solid-walled pipes or conduits.

17. 16. The composition of claim 15, wherein at least a portion of the verifiable and repairable dry tomb biolandfill cycles between aerobic, anoxic, and anaerobic conditions.

18. 1. A means for obtaining carbon credits for biomass sequestration, comprising: a. isolating the biomass in a verifiable dry tomb biolandfill surrounded by top and bottom seals containing at least one barrier to water transport forming a dry tomb structure; b. providing a cover layer comprising soil that serves to protect the enclosed biomass from atmospheric disturbances; c. providing one or more accessible, sealable, true-wall pipes or conduits connected to said enclosed biomass; d. providing a means for monitoring biomass decomposition of said enclosed biomass.

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