A system and method for direct carbon dioxide sequestration

Abstract

A system (100) for carbon dioxide sequestration from woody biomass comprising: a harvesting module (120) for harvesting or collecting woody biomass; a drying module (150) to which woody biomass assessed to have moisture content greater than a threshold moisture content by weight is directed from the harvesting module (120) for drying said harvested woody biomass to a dry state where the dried harvested woody biomass has less than equilibrium moisture content (EMC) by weight; and a storage module (170, 180) for storing and maintaining harvested dried woody biomass assessed to have moisture content less than EMC by weight. The storage module (170, 180) communicates with a gaseous source of carbon dioxide enabling absorption or adsorption of carbon dioxide from a carbon dioxide containing gas onto, or into, the surface of cellulose or CNC contained within the stored dried woody biomass (180) as carbon dioxide containing gas flows through the stored dried woody biomass and dehydration continues. The woody biomass may be selected as a function of its cellulose or CNC content.

Description

A SYSTEM AND METHOD FOR DIRECT CARBON DIOXIDE SEQUESTRATIONTECHNICAL FIELD

[0001] The present invention relates to a system and method for biomass-based carbon dioxide sequestration.BACKGROUND ART

[0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] Existing CO2 sequestration technologies have a number of limitations which result in high capital and / or operating costs, and / or an inability to ensure that CO2 is effectively captured and removed from the atmosphere or from man-made emissions that would otherwise enter the atmosphere, and securely stored for the long term such that the captured CO2 does not re-enter the atmosphere as CO2 or any other “Green House Gas” (“GHG”) particularly methane (CH4). The definition of key technical terms used in this invention such as: Carbon Dioxide (CO2), Carbon Sequestration, Carbon Capture, Green House Gas (GHG), among others, is that provided within the articles of the Kyoto Protocol to the United Nations Framework Convention on Climate Change (“Kyoto Protocol”).

[0004] Existing CO2 sequestration technologies can further be divided into two categories, those (a) currently commercially operational; dominantly the underground sequestration of gaseous CO2 by injection into suitable underground structures and CO2 sequestration in the living biomass of forests and similar biological systems and (b) technologies still being researched, developed, optimised and field tested that as yet display little-to-no commercial operationality. Of the former, underground CO2 sequestration technologies involve the following key steps:

[0005] concentration of CO2 from the atmosphere or an emission source flue to as close to pure (100% CO2) as is practically and economically possible,1 ) compression of high-concentration CO2 to the highest density gas as is practically and economically possible,2) pumping of the high-density gas via interconnected pipelines and drilled wells to allow for the CO2 gas injection into suitably permeable and porous geological strata,3) CO2 gas injection to maximise the volume of gas stored in the strata as far as is practically and economically possible, and4) on achievement of the strata’s gas storage capacity, sealing of the well and the strata with the objective of trapping the CO2 within the strata in perpetuity.

[0006] Underground gaseous CO2 sequestration systems are characterised by the need to have a suitably porous and permeable geological strata for practical and economic CO2 injection, sealing and storage in close proximity to the CO2 collection and / or emission site in order to minimise the construction and operating costs of transmission and delivery pipeline(s). To eliminate the possibility of CO2 contamination of underground water and / or leakage of CO2 from its storage site, the targeted underground CO2 storage strata must also be an acceptable distance below any water-bearing aquifers, which may be an existing, or future, source of potable, agricultural or industrial water.

[0007] The majority of the operating costs of underground CO2 storage is in the concentration of CO2 at or adjacent to the emission and / or collection site and the pumping of the compressed CO2 into the underground strata. If the CO2 emission gas stream has an initially high CO2 concentration and the distance to the storage site is short, and the strata is geologically and geotechnically acceptable and the CO2 gas does not leak from the storage strata, underground CO2 sequestration can be an effective CO2 sequestration technology. If any of the above conditions are not met, underground CO2 sequestration by this means will be cost ineffective and / or not achieve the primary objective of sequestering CO2 in perpetuity.

[0008] Biological CO2 sequestration systems, in contrast, primarily rely on photosynthesis for the collection and concentration of atmospheric CO2 and are characterised by the need to have suitable tracts of the land (or in some cases suitable tracts of sea or seabed) to grow plant biomass and once grown to maturity sustain that biomass such that the total quantum of grown biomass and absorbed CO2 remains constant into the future. To eliminate the possibility of large-scale return of CO2 to the atmosphere requires significant and sustained management to mitigate risks associated with (a) natural disturbances such as wildfires, pests, disease and drought and (b) anthropogenic disturbances such as harvest and deforestation for change of land use.

[0009] Systems of harvesting or collecting biomass for storage and carbon sequestration, for example as described in US Patent Publication No. 20220374912, rely upon sealed biomass storage conditions and the elimination of atmospheric oxygen to mitigate biomass decomposition, conditions more difficult to establish and maintain than those in the Applicant’s ‘Dry Stack’ system as described in International Patent Publication No. WO2024229516, the contents of which are hereby incorporated herein by reference.

[0010] The majority of the costs associated with biological CO2 sequestration systems arise from the extensive areas needed and the fact that those areas may be in competition with other uses such as food or bio-fuel production or an existing conservation purpose. There are also significant costs in the ongoing management of biological CO2 Sequestration systems during their growth phase and once they have reached maturity even long after net removal of CO2 from the atmosphere has ceased. If either effective long term management arrangements are not in place or the natural and anthropogenic risks mentioned above cannot be effectively addressed, biological CO2 sequestration systems will not meet the primary objective of sequestering CO2 in perpetuity.

[0011] There are further CO2 sequestration technologies, often used in an industrial context, including:(a) Absorption systems involving variously amine, carbonate, ammonia, hydroxide and limestone based reagents;(b) Adsorption systems involving metal organics and zeolite based reagents;(c) Membrane systems involving microporous and fibre-based components; and(d) Other technologies involving mineralisation and cold separation systems.

[0012] These CO2 sequestration technologies are not typically suitable for use in combination with sequestration of CO2 via plant-based sequestration.

[0013] It is against this background that the present invention has been developed.SUMMARY OF INVENTION

[0014] The present invention provides, in one aspect, a system for biomass carbon dioxide sequestration from woody biomass comprising:(a) a harvesting module for harvesting or collecting woody biomass;(b) a drying module to which woody biomass assessed to have moisture content greater than a threshold moisture content by weight is directed from the harvesting module for drying said harvested biomass to a dry state where the dried harvested biomass is less than the Equilibrium Moisture Content (EMC) by weight; and(c) a storage module for storing and preserving harvested woody biomass with less than EMC by weight, wherein said storage module communicates via a ventilation system with the atmosphere enabling circulation of air through the storage module and direct adsorption, or absorption of, carbon dioxide from the atmosphere onto, or into, cellulose and cellulose nanocrystals (CNC) that comprises a substantial proportion of the stored harvested biomass.

[0015] The objective of storage of biomass in the storage module, also referred to in this specification (as in the Applicant’s International Publication No. WO 2024229516 incorporated herein by reference) as a ‘dry stack’, is to preserve the biomass and minimise the rate of decomposition. This involves maintaining the biomass in a dry, dark, well-ventilated state ensuring zero or near-zero micro-macro biological decomposition of biomass. The great majority of woody biomass decomposition pathways require free water to initiate hydrolysis and biomass digestion or decomposition. For preservation, stored woody biomass must have moisture content less than EMC and the drier the biomass, the better the conditions for preservation.

[0016] In this specification, ‘Equilibrium Moisture Content’ (EMC) of biomass is defined as the moisture content of the biomass whereby no free water is present on or within the biomass, that is the biomass is in thermodynamic equilibrium with the moisture in the surrounding atmosphere at a given relative humidity, temperature and pressure.

[0017] Dried woody biomass is porous, and at a microscopic level, comprised largely of hollow cellulose tubes bound together within a hemi-cellulose and lignin matrix. The drierthe biomass the less the cellulose tubes are filled with water molecules, the greater the porosity and potential for gas ingress and interaction with surfaces of the cellulose or CNC contained within the stored woody biomass.

[0018] Because atmospheric air contains around 400ppm CO2, the system enables direct carbon dioxide capture from that atmospheric air. Such carbon dioxide capture would typically form a minor portion of carbon dioxide sequestration by the system when compared to direct atmospheric carbon dioxide sequestration in the stored biomass.

[0019] The system conveniently includes a data generation and calculation system that processes data to allow for the calculation of net CO2 removed from the atmosphere and sequestered within the dried biomass and onto, or into, the cellulose or CNC of the stored dried woody biomass where hydroxyl groups of cellulose may act as hydrogen bond carbon dioxide sites. Hydroxyl sites suitable for CO2 hydrogen bonding, also exist on the surface of hemi-cellulose and lignin components of woody biomass, however these molecules are less porous than cellulose and have less potential for gaseous CO2 interaction and thus less CO2 absorption or adsorption potential. Lignin and hemicellulose absorption or adsorption of atmospheric CO2 within dried woody biomass are included in the invention.

[0020] Where harvested woody biomass from the harvesting module is assessed to have less than the threshold moisture content by weight, it may be directed to the storage module without further drying in the drying module. However, this is not intended to preclude direction of all harvested biomass, even of harvested biomass having less than the threshold moisture content, to the drying module either to make operation of the system more practical or efficient.

[0021] Advantageously, the biomass includes above ground biomass (AGB) of woody plants and trees compositionally dominated by lignin, hemicellulose, cellulose (and non- structural carbohydrates) which may be termed “hard celled” AGB, in contrast to “soft celled” AGB typical of commonly cultivated grasses. However, the biomass may also include below ground woody biomass being roots, stumps and lignotubers and soft celled grasses with a high cellulose content. Preferably, AGB or other woody biomass is selected as a function of its cellulose nanocrystal content (CNC) with higher CNC being preferred. A Eucalyptus species may be the preferred source of woody biomass for its fast growth and high biomass yield, as well as its suitability for dry stack storage (as described in International Patent Publication No. WO2024229516 incorporated herein byreference) due to 1 ) the recalcitrance to decomposition of its woody biomass, and 2) for direct CO2 adsorption onto, or absorption into, cellulose or CNC, as described in this specification, due to the high cellulose and CNC content of its woody biomass.

[0022] The system may include a plurality of each of the harvesting module, the drying module and the storage module, each of which may have a determined capacity in weight and / or volume. All stored woody biomass is dried to moisture content below EMC, however due to the ventilation system directing air efficiently within the storage module (or dry stack), biomass dehydration continues within the storage module. Efficient ventilation enhances dehydration and the porosity of the woody biomass, enhancing the capacity of the contained cellulose or CNC to adsorb or absorb CO2, whilst providing a continual fresh supply of undepleted atmospheric CO2 for ongoing adsorption or absorption.

[0023] The harvested woody biomass is desirably processed to control particle size, desirably to a particle size that - while sufficiently large to aid preservation, allows the biomass to flow as a bulk material, and increases the surface area of woody biomass accessible to through flowing atmospheric gas within the storage module. A preferred chunker to reduce the particle size of the harvested woody biomass is described in the Applicant’s International Publication No. WO2024130340, the contents of which are incorporated herein by reference.

[0024] The system conveniently includes a transport module which allows transport of woody biomass between harvesting and drying modules and between drying modules and Dry Stack storage modules. The transport module may comprise at least one vehicle which may be configured in either a harvesting mode or a mobile storage mode, as required. In one embodiment, a vehicle configured for harvesting mode may be as described in the Applicant’s co-pending International Publication No. WO2024130340, incorporated herein by reference.

[0025] The drying module allows drying of the woody biomass. Solar drying is preferred as a cost-effective drying method. Solar drying allows for assistance of drying of biomass by wind flow and dry air. However, other forms of biomass drying are not precluded. The drying module may include one or a plurality of drying stages. Drying may continue until the target moisture content for the dried biomass is reached. Porosity may also be measured, if desired. As the pores of the woody biomass can only be filled with either air or water, a decrease in moisture content is closely correlated with an increase in porosity.During ‘dry stack’ storage in the storage module, as described here, there should be no loss of TOC and no obvious physical changes to the biomass, apart from variations in sub-EMC moisture content; a generally decreasing trend towards a minimum value, for example of around 5% H2O around 180 days from closure of the storage module or dry stack. Decreasing and low moisture levels means many and increasing air filled pores within the biomass, accessible to the atmospheric air flowing through the dry stack, and direct absorption into, or direct adsorption of atmospheric CO2 onto the surfaces of the (cellulose or CNC) pores. Density and porosity may be measured, conveniently by standard laboratory techniques.

[0026] The storage module (or “dry stack”), as described in the Applicant’s International Publication No. WO202429516 incorporated herein by reference is desirably configured for preservation of woody biomass being water proof and insect proof as well as free from light and dry. In particular, the storage module should be termite proof. Termite proofing desirably avoids use of chemical insecticides, but may include the use of chemical insecticides in the event that termites breach the termite barrier. In one embodiment, the storage module may be located on ground having a termite barrier separating the storage module from the ground. The termite barrier may comprise a contiguous saline soil layer, conveniently comprising or consisting of sodium chloride in excess of 1 % NaCI by weight. Such a saline layer is toxic to termites. The storage module is also desirably both dark (i.e with a substantial absence of light) and fireproof.

[0027] The storage module further comprises a ventilation system for circulation of atmospheric gases through the stored dry biomass to enhance and maintain biomass dryness, prevent biomass decomposition, enhance biomass porosity and improve access to, and ingress of atmospheric gases into the dried biomass. The ventilation system may comprise a system of inlet pipes extending through the stored biomass, conveniently as described in the Applicant’s International Publication No. WO2024229516 incorporated herein by reference. Pipes may open outside the storage module for ingress of atmospheric air for circulation through, and ventilation of, the storage module or dry stack. The ventilation system preferably comprises at least one ventilation exhaust stack extending beyond the stored biomass. The ventilation exhaust stack may be modular, allowing a length of the ventilation stack to be modified dependent on quantity of stored biomass.

[0028] The ventilation exhaust stack may include an extractor fan for creating a draft or the ventilation system may use passive air movement technologies, to draw air from the atmosphere and through the stored biomass. Desirably, any extractor fan is powered by renewable energy such as wind or solar power.

[0029] Air drawn from the atmosphere by the ventilation system and through the stored biomass contains a portion of carbon dioxide, about 0.04% or about 400ppm. Interaction of the atmospheric CO2 with the stored dried woody biomass allows for direct absorption into, or adsorption of CO2 onto the surface of cellulose and CNC of the woody biomass. Porosity of the biomass, ingress of atmospheric CO2 and direct absorption or adsorption of CO2 is dependent on the residual moisture level of the biomass, being as low as possible below EMC and preferably below 10 wt% to achieve effective direct absorption or adsorption of carbon dioxide. Such air preferably has as low relative humidity as possible, achieved due to site specific climatic conditions or as achieved by air dehumidification. Increases in Relative Humidity during and immediately after rainfall events have a short-lived impact and negligible impact on the moisture content of biomass stored in Dry Stack conditions and as such CO2 absorption or adsorption as described in this invention.

[0030] The storage module also desirably further comprises a measuring and monitoring system which enables biomass sampling and analysis; and exhaust gas sampling and analysis, with the objective of generating data, and the analysis thereof, to calculate net CO2 removed from the atmosphere and sequestered within the stored dried biomass and onto the surface of, or into the cellulose or CNC of the dried biomass. Net CO2 removed from the atmosphere and sequestered is eligible for verification and validation as a carbon dioxide removal credit. The biomass sampling and analysis attributes may include: the weight of all biomass stored in the Dry Stack, the biomass moisture content, Total Organic Carbon (TOC), Total Nitrogen content, ash content, cellulose, hemi-cellulose, lignin, non- structural carbohydrates among others.

[0031] Desirably, the woody biomass is representatively sampled and analysed for moisture and total organic carbon (TOC) as it is deposited onto a storage pad of the storage module or dry stack. Biomass is also sampled for moisture and TOC regularly after deposition and closure of the storage module. In concert with multi-element (desirably including carbon monoxide, carbon dioxide and methane) exhaust gas analysis, the generated data can be used to demonstrate preservation by zero or nearzero loss of TOC, and zero to near zero return of CO2 to the atmosphere over a determined time period, typically as set by a carbon accreditation agency. Corresponding carbon credits or CDRs can then be issued.

[0032] Biomass TOC and moisture content data at the point of closure of the storage module is typically required for the calculation of carbon dioxide removed from the atmosphere and sequestered within organic molecules that comprise the dried biomass as well as onto the surface of, or into, cellulose or CNC. Gross CO2 removed from the atmosphere is the weight of biomass multiplied by the average biomass TOC at the point of closure of the storage module. Regular sampling and TOC analysis of woody biomass over time is required to demonstrate that the target TOC loss (i.e zero for effective preservation and CO2 sequestration and associated carbon credits) is achieved. TOC values of the woody biomass in excess of that at the point of closure of the storage module and the commencement of storage represent CO2 absorbed into, or adsorbed onto the surface of cellulose or CNC or lignin or hemi-cellulose as the case may be.

[0033] Exhaust gas sampling and analysis may include, without limitation, monitoring relative humidity, temperature, CO2, CO and CH4 content, with minimum detection limits for each gas less than atmospheric concentrations. Monitoring demonstrates the longterm effectiveness of the Dry Stack biomass carbon dioxide sequestration system and cellulose or CNC direct adsorption or absorption of CO2 methodology as described herein. Further, each biomass sampling site and gas sensor desirably has its spatial position (e.g in x-y-z frame or polar coordinates) within the storage module recorded. The biomass and gas compositional and physical data, together with position recordal, conveniently allows defects in the storage module allowing undesirable moisture permeation to be located and addressed.

[0034] The storage module has a structure preferably being an impermeable robust plastic membrane, preventing migration of moisture into the stored biomass and which also seals the stored biomass from the atmosphere ensuring substantially all access to the atmosphere is via the ventilation system. All gases emanating from the Dy Stack are directed through the exhaust stack, or other exhaust means of the ventilation system, and as such compositional analysis of the exhaust gases reflects conditions within the storage module also referred to as a Dry Stack. Such a structure may comprise a base layer preventing upward migration of moisture into said stored biomass and a roof structure preventing downward and / or lateral migration of moisture into the stored biomass. Thebase layer may be formed from a material selected from the group consisting of clay, soil, impermeable plastic (polymer) membrane and a combination of these materials to form a water impermeable barrier. Such a barrier also excludes entry of other agents that may cause deterioration of the stored biomass and is further desirably fireproof. The roof structure may also be configured, for example by selection of material and / or material thickness, to reduce or avoid light ingress into biomass stored in the storage module.

[0035] In another aspect, the present invention provides a method for biomass carbon dioxide sequestration from woody biomass comprising:(a) harvesting or collecting biomass;(b) drying said harvested biomass where harvested biomass is assessed to have moisture content greater than a threshold moisture content by weight so that the dried harvested biomass has less than the threshold moisture content by weight;(c) storing said dried harvested biomass assessed to have moisture content less than EMC,(d) communicating said stored dried harvested biomass with a source of carbon dioxide containing gas;(e) capturing carbon dioxide from the source of carbon dioxide containing gas by absorption into, or adsorption of carbon dioxide onto the surface of cellulose and cellulose nanocrystals (CNC) contained within said stored dried harvested biomass as said carbon dioxide containing gas flows through the stored dried harvested biomass to enable carbon dioxide sequestration; and(f) generating and analysing data to calculate net CO2 removed from the source of carbon dioxide containing gas and sequestered within the dried woody biomass.

[0036] The method should also include monitoring to demonstrate that CO2 remains sequestered within the dried woody biomass over time. Desirably, determined sampling and analysis steps can be followed to demonstrate such CO2 sequestration without return of CO2 to the atmosphere.

[0037] The method may include other features as described above with reference to the system for biomass carbon dioxide sequestration. As above, the object is to store the dried harvested biomass in a substantially dry and preserved state.

[0038] Biomass is preferably harvested according to its cellulose and cellulose nanocrystal content (CNC). Thus, a Eucalyptus species with high cellulose and CNC content, may be a preferred source of woody biomass.

[0039] The current invention has a number of potential advantages including removing and sequestering extra CO2 from the atmosphere, above and beyond that removed and sequestered within the structure of the inherent organic molecules (dominantly cellulose, hemicellulose, lignin and non-structural carbohydrates) that comprise the woody biomass itself. The extra CO2 absorbed into, or adsorbed onto the surface of cellulose or CNC is a beneficial by-product of the effective construction and operation of the storage module or Dry Stack, specifically the storage of dried woody biomass (atmospherically) well- ventilated conditions.Further, the Dry Stack and direct cellulose or CNC absorption or adsorption and sequestration system of the present invention, allows for possibility for storing woody biomass on marginal agricultural land. The direct cellulose or CNC absorption or adsorption and sequestration system of the present invention is simple and relatively inexpensive of construction and operation in comparison to other systems of direct air capture of CO2 and CO2 sequestration.BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further features of the system and method for direct carbon dioxide sequestration of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

[0041] Figure 1 is a schematic diagram of a system for dried woody biomass carbon dioxide sequestration and direct absorption or adsorption of CO2 onto cellulose or CNC of woody biomass, according to one embodiment of the present invention.

[0042] Figure 2 is a schematic plan view of a biomass plantation showing relative positioning of harvesting and drying modules of the system of Figure 1 .

[0043] Figure 3 is a schematic plan view of the site of a biomass storage module showing a biomass storage pad for a biomass storage facility and associated earthworks.

[0044] Figure 4 is a schematic end view of the site of the biomass storage pad as shown in Figure 3.

[0045] Figure 5 is a partial end view of the biomass storage pad as shown in Figures 3 and 4 and showing a biomass stack including its ventilation system.

[0046] Figure 6 is a partial side view along the short axis of biomass storage pad of the same construction as shown in Figures 3 to 5 and showing the stacking arrangement.

[0047] Figure 7 is a schematic side view of a stacking system for a biomass stack such as that shown in Figure 5.

[0048] Figure 8 is a graph showing dried biomass total organic carbon (TOC) over storage time in the biomass stack of Figure 5.

[0049] Figure 9 provides scanning electronic microscope images of natural Eucalyptus grandis samples in the cases of a) sapwood, b) heartwood, c) pith and d) showing a typical cross section of E. grandis wood.

[0050] Figure 10 is a graph showing dried biomass moisture content (wt%, y axis) over storage time (days, x-axis) in the biomass stack of Figure 5.

[0051] Figure 11 is a flow diagram showing operation of the system of Figure 1 .

[0052] Figure 12 is a schematic showing bonding of carbon dioxide to hydroxyl groups of cellulose.DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] Referring now to Figs. 1 and 2, there are shown the component modules of a system 100 for biomass carbon dioxide sequestration, for example the system described in the Applicant’s International Patent Publication No. WO2024229516, also referred to in this specification as a ‘dry stack’ carbon dioxide sequestration system and further description of which is incorporated herein by reference. In preferred embodiments, thebiomass includes above ground biomass (AGB), i.e. woody biomass, of woody plants and trees compositionally dominated by lignin, hemicellulose, and cellulose, which may be termed “hard celled” AGB, in contrast to “soft celled” AGB typical of commonly cultivated grasses. However, the biomass may also include soft celled grasses with a high cellulose content Further description of candidate woody plants as a source of AGB is provided below.

[0054] System 100 includes a harvesting module 120, a drying module 150 and a storage module 170.

[0055] Harvesting module 120 allows for harvesting or collecting biomass assessed to have a substantial proportion of moisture. A ‘substantial proportion of moisture’, in the embodiments, is a moisture content in excess of a threshold, pertinently in preferred embodiments the equilibrium moisture content (EMC) as understood in the art of wood processing and use. A “minor proportion of moisture” in the embodiments may be used to describe a moisture content below EMC. EMC of biomass may be defined as the moisture content which is in thermodynamic equilibrium with the moisture in the surrounding atmosphere at a given relative humidity, temperature and pressure.

[0056] Drying module 150 allows initial drying of the harvested biomass, where necessitated by its moisture content being assessed as above EMC, to a dry state in which said biomass has a minor proportion of moisture, i.e. a moisture content below a threshold level. A ‘minor proportion of moisture’, in the preferred embodiments, is a moisture content of less than about 20%, for example between 10% and 15% by weight. Without wishing to be bound by theory, this moisture content, or the equivalent water activity, is below EMC eliminating any available free moisture required for microbial metabolism and growth and consequential biomass decomposition. Thus the dried biomass is able to be stored in an inert state, permanently sequestering photosynthetically captured CO2 out of the atmosphere.

[0057] To achieve such required low moisture content, or water activity, drying module 150 comprises a biomass drying facility. In the event of harvesting or collecting biomass assessed to already be dried to below EMC, this step can be skipped and dried biomass can be transported directly to the storage module 170.

[0058] Biomass moisture content may be assessed in a number of ways. A simple methodology based on weight involves first weighing the biomass (termed the greenweight), dehydrating the biomass in a heater or oven at a selected temperature for selected duration to enable water to evaporate and then weighing the biomass again (this being the ‘dry’ weight). The difference between the two weight measurements is the assessed moisture content. In one embodiment, the selected temperature may be 50°C and the selected duration 5 hours. Other methods of moisture assessment, for example employing moisture meters or sensors, could be used.

[0059] Storage module 170 allows for storage and maintenance of harvested biomass in a substantially preserved and dry state. Storage module 170 comprises a biomass storage facility 172 with at least one biomass dry stack 180.

[0060] System 100 also includes a transport module 200 which allows transport of biomass between harvesting module 120 and drying module 150 and between drying module 150 and storage module 170. The transport module 200 here comprises a range of vehicles which may be configured in a harvesting mode and stacking mode as described below. In one embodiment, a vehicle 1100 configured for harvesting mode may be as described in the Applicant’s International Publication No. WO2024130340, incorporated herein by reference. Vehicle 1100 has a chunker to cut biomass into a selected particle size suitable for direction to the drying module 150 however unprocessed woody biomass or woody biomass processed in any other way, may also be suitable for drying and storage.Biomass Drying Facility (BDF)

[0061] Fresh AGB biomass, AGB biomass being as above described and described in further detail below, is deposited from a biomass transportation vehicle onto biomass drying facility (BDF) 152 which comprises a drying pad 154 and a dedicated biomass recovery machine 210, these items being shown in the Applicant’s International Patent Publication No. WO2024229516, incorporated herein by reference.

[0062] BDF 152 is located adjacent biomass storage facility (BSF) 172 as shown in Fig. 2. In this embodiment, both BDF 152 and BSF 172 are located close to the geographic centre of a biomass production plantation 300 from which the AGB biomass is sourced to minimise the biomass transportation distance.

[0063] The BDF 152 and BSF 172 may, in embodiments, be located within an area of sufficient surface area to construct a number of similar purpose-built BSF facilities to accommodate future biomass production. The BDF 152 can be used for repeated harvestand storage events occurring, for example, approximately every two years. It will be understood that, in other embodiments, harvest events can occur at different frequency.

[0064] Advantageously, the BDF 152 and BSF 172 are located on the margin of natural or human-induced salt flats or salt lakes, land with no vegetation (other than the biomass production plantation 300) and usually having a variable thickness crust of salt in a climatic zone where evaporation greatly exceeds precipitation. Similarly degraded or low production land including salinated, hardpanned or wind-blow or rocky land or irregularly shaped cultivated land that is difficult to economically cultivate, would also be suitable for the BDF 152 and BSF 172. While other embodiments may enable other forms of land to be used, land as above described is plentiful across the Australian continent.

[0065] The BDF drying pad 154 is a flat area of land, conveniently as above described, with little to no preparation required. Drying pad 154 has high direct exposure to sunlight and heat to enable biomass drying by solar or sun drying.

[0066] Fresh woody biomass may have a moisture content between 35% and 55% by weight, typically around 45% by weight as assessed by a method such as that described above. The chunked fresh biomass is dumped from a mobile transport vehicle conveniently a truck-based tipper, or a similar mobile bulk handling cart capable of transporting an economically viable weight of low density biomass, onto the BDF drying pad 154 in rows. The rows may in such case be, for example, around 3m wide and 2.5m high. A front end loader with a large biomass push rake may be used to level the rows into as flat, even and continuous layer as is practical. The layer of chunked fresh biomass has thickness to optimise drying time with available surface area and available labour for operating the mobile transport vehicle and front end loader.

[0067] The layer of chunked woody biomass is allowed to dry undisturbed on the BDF drying pad 154 until it is assessed to have a moisture content of less than EMC, preferably below about 20% by weight and preferably between 5 and 15% by weight, for example 10% by weight.

[0068] During drying, the biomass is sampled and analysed for moisture content, moisture content being assessed for example by the method described above. When a determined minor proportion of moisture is present, the biomass is recovered from the BDF drying pad 154 for transport and delivery to the BSF 172.Recovery of Dried Biomass

[0069] Dried biomass 156 is recovered from the BDF drying pad 154 and loaded into a biomass transport vehicle, conveniently a truck based tipper or a similar mobile bulk handling cart capable of transporting an economically viable weight of low density biomass, with a front end loader equipped with a low tare weight, large capacity, biomass bucket. Suitable buckets are known in the art of front end loaders and truck based tippers. The operational capacity of the front end loader is matched to that of the biomass transport machine(s) and the biomass stacker to ensure an optimal biomass material flow rate.

[0070] Alternatively, the dried biomass may be recovered from the BDF drying pad 154 and loaded into a biomass transport vehicle, conveniently a truck-based tipper, tipper or a similar mobile bulk handling cart capable of transporting an economically viable weight of low density biomass, with a mobile biomass recovery machine (BRM), that continuously picks up the dried biomass, temporarily stores it on board and then delivers it to the biomass transport vehicle. The BRM has common features with the harvester machine of the Applicant’s International Publication No. WO2024130340, the contents of which are incorporated herein by reference.Biomass Storage Facility

[0071] In a preferred embodiment, as indicated in Figures 3 and 4, biomass storage facility 172 and a storage pad 174 accommodating it is located on the margin of natural or human-induced salt flats or salt lakes 173 in one example characterised by a thick, high clay content salinated soil 173E. The soil layer may be > 2m thick with >30% clay with electrical conductivity >16ds / s and TDS >10000ppm (mostly as NaCI). The clay content of the soil is sufficient to ensure that, upon optimal compaction, the soil has hydraulic conductivity less than 10’9ms-1. There is an abundance of such land in Western Australia and other parts of the globe.

[0072] Often, such soils have a saline (e.g. 10000ppm TDS typically as NaCI) to hypersaline (e.g. 250000ppm TDS typically as NaCI) ground water table 179 which may, for example, be located 500mm to 1500mm below natural ground level and usually around 700mm below natural ground level. A halite dominated salt crust is often present on the soil surface as well. The halite crust may, for example, have a thickness of 1 -20mm.

[0073] Advantage is obtained where the salinated soil at the site contains greater than 1 % NaCI, particularly where there is a continuous soil horizon of determined thickness, for example no less than 50mm thick and conveniently about 1 m thick.

[0074] Although not as advantageous, if naturally salinated soils are not available, any relatively flat, high clay content soil site may be used to construct the BSF 172. In such cases, a salt (most conveniently NaCI for reasons that will become apparent below) may be added to and incorporated into a top layer of the soil where the BSF 172 is to be located. In the event that high clay content soil is not readily available, any soil can be utilised, with appropriate attention to compaction to mitigate moisture ingress and soil erosion.

[0075] The BSF storage pad 174 may be constructed with earthmoving machinery, typically involving a bulldozer, motor grader or front end loader. The soil is excavated or graded, to form a spoon drain or shallow trench 176 adjacent to, and surrounding, the BSF storage pad 174. The soil from the spoon drain or shallow trench is pushed up to form the BSF storage pad 174 (as shown in Figures 3 and 4). In an exemplary embodiment, the BSF storage pad 174 is between 200mm and 1500mm above, for example about 500mm above, the natural ground level at the centre.

[0076] Woody biomass storage pad 174 has a low angle (1 :100) slope down from the centre to the edge. The storage pad 174 may be any desired size though for benefit, in terms of economies of scale, exemplary dimensions would be at least 10m wide and preferably about 50m wide, with length at least 50m and preferably about 200m.

[0077] The excavated spoon drain or shallow trench 176 around the BSF storage pad 174 forms a shallow drain or sump, lower than the natural ground level enveloping the storage pad, being salt lake or salt flat or any other low productivity or suitable soil 173. The trench 176 thus provides an evaporation sump for rainfall that falls on the BSF storage pad 174. Surface water collects in the trench 176 and is evaporated.

[0078] On the outer edge of trench or drain 176, a bund 177 is constructed encircling the biomass storage facility 172. The bund 177 does not have to be circular in shape and could, for example, be rectangular as shown. Soil to construct bund 177 is conveniently sourced from a shallow trench adjacent to the bund 177. The soil is pushed up with earthmoving machinery, conveniently a bulldozer or front end loader.

[0079] The bund 177 should have height greater than anticipated floodwater level over a substantial timeframe. For example, the height is preferably higher than the level for a rainfall and flooding event that the site would experience in at least 1 in 100 years, more preferably a 1 in 1000 year rainfall and flooding event to provide great security of biomass carbon dioxide sequestration. For the site shown in Figures 3 and 4, bund 177 has height greater than 500mm, more preferably greater than 1000mm and, for example, 1500mm. It will be appreciated that such height varies with location and flood risk.

[0080] Once the natural or created salinated soil is pushed into place to form the shape of the BSF storage pad 174, the surface is scraped or bladed with an earthmoving machine, ideally a motor grader, to be as even as practical with a slope (for example of about 1 in 100), down away from the centre line, C, of the long axis of the BSF storage pad 174.

[0081] For the site shown in Figures 3 and 4, the salinated soil 173E of the salt lake 173 is naturally moist, typically having a moisture level conducive to compaction of soil 173E. Such moisture level may be in the range 12 to 18 wt% moisture, for example about 14 wt% moisture as assessed, for example, by a soil moisture meter. If the salinated soil 173E moisture is below the desired range, water may be sprayed on the surface, prior to compaction, to achieve that level in the uppermost soil horizon of the BSF storage pad 154. The uppermost soil horizon layer is preferably at least 50mm thick, more preferably about 100mm thick.

[0082] Where water is sprayed over the soil surface, care is to be taken not to over water the soil and, desirably, no water run-off should occur. Once the target soil moisture is achieved, the BSF storage pad 154 is compacted with a mobile compactor designed to efficiently compact the surface and construct a surface hard pan with very low hydraulic conductivity as described above.

[0083] Where a soil is not salinated, the soil is pushed up and scraped or bladed as flat as practical, in the same manner and in the same dimensions as described for the salinated soil. A similar encircling bund 177 is provided to mitigate flooding from at least a 1 in 100 year rainfall or flood event for the site.

[0084] Once the non salinated pad is even and of the design slope, and prior to compaction, it is cultivated to a selected depth with an agricultural tillage implement. Selected depth is preferably at least 35mm, more preferably about 75mm. Theagricultural tillage implement conveniently comprises tines, preferably spaced up to about 150mm apart. In embodiments, the agricultural tillage implement forms harrows in a configuration typical for cereal crop seed preparation. NaCI is then evenly applied to the harrows in the surface at an application rate desirably greater than 10kg / m2, for example about 13 kg / m2The prepared BSF storage pad 174 surface is then again cultivated with the same tillage equipment to incorporate the NaCI into the prepared surface horizon of nature as above described. The surface of the BSF storage pad 174 is then scraped or bladed with the motor grader or other earthmoving machinery to be as flat and even as practical.

[0085] The volume of material above the natural ground surface, S, that comprises the BSF storage pad 174 acts to reduce upward moisture migration towards the biomass stack 180, hereon referred to as dry stack 180. The surface hardpan of the BSF storage pad 174 acts as an additional dampcourse to further inhibit upward migration of moisture into the dry stack 180. Such moisture creates a risk of biomass decomposition and loss of carbon dioxide sequestration. Further, dry stack 180 is provided with a roof structure 182, for example of plastic membrane or compacted clay soil cover, as described below, acts to eliminate downward and lateral migration of moisture from rainfall events into the dry stack 180. In this way, the biomass within the dry stack 180 is kept dry and dark, both factors that are important to preservation and effective biomass carbon dioxide sequestration.

[0086] The greater than 1 % NaCI content of the salinated soil is also selected to create a hostile, toxic environment for termites which would digest the biomass, ultimately release carbon dioxide or other greenhouse gases, and defeat the purpose of sequestration. Termites cannot survive in the saline conditions described. The saline environment of the salt lake or salt flat and the saline soil horizon of the storage pad whether natural or created, 174 act as biological termite barriers. The salt remains in place in the salinated soil 173E and is not removed being protected by the biomass stack 180 covering the storage pad 154. The dry nature of the biomass stack 180 is a further deterrent to termites which prefer wood with moisture above EMC.

[0087] In some embodiments, at the completion of the dry stack 180 and the cessation of earthmoving and heavy machinery movements, termite traps comprised of untreated termite-friendly woody biomass baits, conveniently inside an accessible container around 150mm in diameter, are buried with the top of the trap just below surface level and eachtrap being around 2m outside the edge of the stack and spaced apart, for example 2m apart, so that the traps form a continuous chain of traps enveloping the dry stack 180. Termite traps are regularly monitored for termite activity adjacent to the dry stack 180. In the event of termite activity being detected, conventional chemical termiticides are applied to the stack’s ventilation system 184 inlet pipes in accordance with product handling and specifications for use. Termite traps are re-baited with woody biomass and regular monitoring resumes for subsequent termite treatment as necessary. Other termite mitigation strategies may be employed in other embodiments, the foregoing being merely illustrative of one strategy.

[0088] At this point, the BSF storage pad 174 is ready for installation of a ventilation system 184 prior to the deposition, stacking and covering of the dried biomass.

[0089] Ventilation system 184 is provided to ensure efficient air ventilation of the dry stack 180 by an at least adequate throughflow of air from the outside through the dry stack 180. Given that the climate for the biomass carbon dioxide sequestration system 100 is characterised by annual pan evaporation greatly exceeding annual rainfall, ambient air is substantially of low moisture content such that the overall effect of air flow from ventilation system 184 is drying such that the biomass stack 180 is kept dry, a key element assisting in preservation of the biomass (and effective carbon dioxide sequestration) within dry stack 180. Further dehydration also occurs during dry stack storage being enhanced by air ventilation.

[0090] In an embodiment, for example as shown in Figure 5, the ventilation system 184 comprises a network of inlet and exhaust pipes 185 which allow for atmospheric air to be drawn into the dry stack 180, uniformly distributed throughout the the biomass stack and exhausted from the dry stack 180. The atmospheric air, contains about 0.4 wt% carbon dioxide and is therefore a source of carbon dioxide gas which can also be captured by direct absorption into, or adsorption onto the surface of cellulose and cellulose nanocrystals (CNC) of the dry stack 180 as described below.

[0091] In exemplary embodiments, a plurality of spaced inlet ventilation pipes 185 are laid on the surface of the storage pad 154, for example with their long axis directed towards and at right angles to the edge 154a of the storage pad 174. The inlet ventilation pipes 185A extend a distance beyond the edge of the storage pad 174. Once stacked biomass is covered by roof structure 182, the inlet ventilation pipes 185A facilitate the flow of air from outside to inside a storage chamber 181 of dry stack 180.

[0092] Dry stack 180 further includes one or more exhaust ventilation stacks 187, one of which is centrally located and shown in Figure 5. The exhaust ventilation stack 187 desirably extends vertically and is, like the ventilation pipes 185, desirably perforated along its length. If a plurality of exhaust ventilation stacks 187 are provided, they are spaced apart, for example 5m, 10m, 15m or 20m apart. Each exhaust ventilation stack 187 must extend beyond the uppermost height of the dry stack 180 a distance not less than 1 ,0m, optionally 1 ,5m, optionally 2m and, for example, around 2.5m. As air flowing through ventilation stack(s) 187 is not expected to contain more than atmospheric concentrations of greenhouse gases, such as methane, carbon monoxide andcarbon dioxide. This air would typically have a low average annual relative humidity (37%) in the preferred high evaporation and low rainfall locations of the dry stack 180.

[0093] If required, in particular whilst the dry stack 180 is being stacked with biomass, exhaust ventilation stack(s) 187 may be held in place in a vertical position by support means selected from the group consisting of guy wires, ropes or fixtures fixing the exhaust ventilation stack(s) 187 to the storage pad 154. Such support means may be removed once the dry stack 180 is sufficient to hold ventilation stack(s) 187 in place.

[0094] Alternatively, or additionally, exhaust ventilation stack 187 may be conveniently modular and may comprise a plurality of sections, conveniently of defined length though it is not necessary for each ventilation section to have the same length. Such sections may be connected together to form the or each ventilation stack 187.

[0095] Each of the vertical exhaust ventilation shaft(s) 187 may be equipped on the top end with an extractor fan 186 which is desirably operated with renewable energy, for example the extractor fan 186 is wind powered. The extractor fan 186 creates an airflow through ventilation pipes 185A and an upward draft inside each ventilation shaft 187. Alternatively the exhaust ventilation shaft(s) may rely upon passive wind venturi type extraction of exhaust gases and not utilise an exhaust fan. As shown in Figure 4, exhaust ventilation shaft 187 may have a plurality of branching smaller diameter pipes 185 connected to the exhaust ventilation shaft 187. The arrangement of inlet pipes 185, 185A, exhaust ventilation shaft 187 and extractor fan 186, or passive wind venturi effect, allows air to be drawn into the biomass stack 180 via the inlet pipes 185, circulated through the dry stack 180 and exhausted via the uppermost opening of the exhaust ventilation shaft(s) 187.

[0096] As indicated in Figures 6 and 7, dried biomass 156 recovered from the BDF drying pad 154, or if the dried biomass is below EMC at the point of harvest transported direct from the field, is delivered to the BSF storage pad 174 by biomass transport machine, i.e. truck tipper or similar bulk handling mobile cart, 330, as described above.

[0097] Upon arrival at the BSF storage pad 174, all dried biomass loads (or loads having harvested biomass with moisture content assessed already below EMC without drying) are weighed to determine the biomass payload of each load and cumulatively the total weight of dried biomass that is deposited, stacked and stored on the storage pad 174.

[0098] Weighing can be achieved by any appropriate payload weighing technology including electronic load cells mounted within the biomass transport vehicle 330, or portable electronic weighpads or a portable or fixed weighbridge. All individual payload weights are recorded and summed together to determine the total weight of biomass stored on the Storage Pad.

[0099] Data may also be gathered to measure: density, via standard laboratory techniques including air or water displacement to measure the volume and weight, of a biomass sample; density being weight I volume (kg / m2). Porosity being pore volume I surface volume may be measured via fluid displacement (water-saturated and dry weight and sample volume data), mercury intrusion porosimetry, X-ray computed tomography, or nitrogen absorption.

[0100] The gathered data is critical for the calculation of net CO2 removed from the atmosphere and sequestered within the dried biomass and on the surface of cellulose and CNC of the biomass by monitoring and measurement system 400 as shown in Figs. 1 and 11. The other critical data for the calculation of net CO2 removed from the atmosphere is the average TOC of the stored biomass from biomass sampling and analysis described above and below. The biomass weight is multiplied by the statistically valid average TOC (on a bone dry basis) of the sampled biomass to determine the total quantum of carbon sequestered within the dry stack 180. Gross CO2 removed from the atmosphere and sequestered in the dry stack 180 is the total carbon stored within the dry stack 180, multiplied by the molecular weight of CO2 (44) divided by the molecular weight of carbon (12).

[0101] Net CO2 removed from the atmosphere is effectively gross CO2 minus emissions from the construction and operation of the dry stack 180, via an industry standard Life Cycle Analysis (LCA).

[0102] Biomass stacker 175 then allows stacking of the biomass in dry stack 180 of selected height, here 20m, though this can be selected depending on costs of equipment required to perform the stacking operation and biomass throughput to BSF 172. Alternatively, the biomass may be stacked by a number of different mobile machines including Front End Loader, wheeled or tracked dozer, excavator with hydraulic grab or log loader.

[0103] In a stacking operation, dried biomass 156 may be unloaded from the truck tipper or similar bulk handling mobile cart 330 into a biomass unloader unit 190 located adjacent to a mobile biomass stacker 175. The biomass unloader unit 190 receives the dried biomass and loads the dried biomass into the hopper 175A of the biomass stacker 175 as shown in Figures 6 and 7. Biomass stacker 175, in the embodiment shown, includes a frame 175B supporting a belt conveyor 176, a hydraulic ram system 1177 to raise frame 175B to a height required for stacking. The biomass stacker is driven by an operator located in operator cabin 175C.

[0104] Biomass unloader unit 190 may be provided in a range of configurations. In some embodiments, it may not be required. In the embodiments described here, mobile biomass unloader unit 190 allows biomass to be tipped from truck tipper or similar bulk handling mobile cart 330 on to a conveyor 192 that feeds hopper 175A of the biomass stacker 175. In the embodiment shown in Figure 7, biomass unloader unit 190 has a platform 193 on to which the truck tipper or similar bulk handling mobile cart 330 can be reversed over a ramp 191 for delivery of biomass to the hopper 175A.

[0105] Alternatively, the dried biomass could be unloaded from the truck tipper or similar bulk handling mobile cart 330 into a pile adjacent to a mobile biomass stacker 175 and loaded into the hopper of biomass stacker 175 with a front end loader equipped with a low tare weight, large capacity, biomass bucket 1120, as described above. The hopper forms the materials entry point for mobile biomass stacker 175, materials here including biomass and some soil.

[0106] In embodiments, the mobile biomass stacker 175 is located on the centre line of the long axis of the BSF storage pad 174. The capacity of biomass stacker 175 tomove the biomass and soil (as described below) from the biomass (and soil) hopper to the top of the biomass stack 180 (for example 20m in height), and to efficiently fill the BSF storage pad 174 with stacked biomass and soil covering, is matched to:• the height and width of biomass stack 180;• the size of the BSF storage pad 174; and• the capacity of the BRM 320 and biomass transport machine(s) 330.

[0107] The hopper of stacker 175 conveniently holds at least a single bucket load of biomass from biomass bucket 1120 allowing the biomass transport machine 330 to return for loading at the BDF 150 while the dumped load of biomass is loaded and stacked. Multiple biomass transport machines 330, conveniently truck based tippers or similar bulk handling mobile carts, may be deployed and in operation dependent on the capacity of the biomass carbon dioxide sequestration system 100.

[0108] Dry stack 180 construction conveniently starts at one end 174a of the BSF storage pad 174. Dry stack 180 grows longitudinally in a direction parallel to the long axis of the BSF storage pad 174 as the biomass stacker 175 incrementally moves, in direction shown by arrow ST, toward the other end 174b of the BSF storage pad 174 as indicated in Figure 7.

[0109] Mobile biomass stacker 175 is able to move biomass from the hopper 175A by conveyor 176 onto the top of the dry stack 180, biomass falling onto the dry stack 180 in direction B. Fresh dried biomass is continuously added to the top of the dry stack 180 growing the stack at its natural angle of repose, until the base of the dry stack 180 extends to a determined relatively short distance, for example 1 m, short of the short-axis edge of the BSF storage pad 174 which corresponds with end 174b of storage pad 174.

[0100] Dry stack 180 can be constructed in various ways, the following being illustrative of just one method of construction. In one alternative embodiment, the biomass stack 180 is built as follows: after the payload of transported dried biomass has been weighed, the biomass transport machine(s) 330 dump the dried biomass load directly onto the BSF storage pad 174, with each subsequent load adjacent to the previous load forming a mostly continuous flat stack of biomass around 2m thick.

[0101] A Front End Loader (FEL) or equivalent tractor, with an push up rake blade extending between 5 and 15m beyond the front wheels of the FEL or tractor (similar to that used to push up silage or grain stacks), is positioned at right angles to the stack edge. The push up rake blade is lowered to ground level at edge of the biomass stack 180.

[0102] The FEL I tractor is driven forward with the rake blade rising at the same rate as forward motion of the FEL I tractor to move the outermost biomass towards the centre of the stack and create as steep as possible angled outside edge to the biomass stack 180. The rake blade is repositioned adjacent to the previous position of pushing up and the operation is repeated, until the entire stack edge has been pushed up. The pushing up of the biomass is continued until the stack footprint is as small as possible and the outside walls are as steep as possible. Advantageously, the outside walls of the dry stack form a continuous flat surface to the centre ridge of the biomass stack. Alternatively, the dry stack could be constructed by pushing the biomass into a stack with a wheeled or tracked dozer, or lifted and placed into the stack with an excavator equipped with a hydraulic grab or a log loader.

[0103] Once the dry stack 180 reaches design height and basal width, the mobile stacker 175 is moved a short distance, for example about 1 m, in a direction parallel to the long axis 174L of the BSF storage pad 174 and in a reverse direction towards end 174a of BSF storage pad 174. The object is to ensure that the biomass stack 180 grows evenly and longitudinally in a direction parallel with the long axis 174L of BSF storage pad 174 until filled to capacity with stacked biomass.

[0104] Once the stacking of the dried biomass is complete, the dry stack 180 is ready for the installation of a protective roof structure including the use of an impermeable plastic membrane 182 to keep the stacked dried biomass dry and dark and to eliminate the impact of rain ingress into the dried biomass within dry stack 180.

[0105] Once the entire BSF storage pad 174 is filled with stacked biomass, the mobile biomass stacker 175 is moved from the storage pad 174 to a location adjacent to the storage pad 174. The top of stacker 175 outload is directed towards the centre of the dry stack 180 and at right angles to the edge of the BSF storage pad 174. The hopper of the biomass stacker 175 is filled with relatively dry, high clay content soil, but if an impermeable membrane 182 is used as a roof structure, then the soil cover layer can be any soil type but conveniently the same as that used to construct the BSF storage pad174. The soil cover layer, typically being of incombustible material, also ensures fire proofing.

[0106] The soil is transferred to the hopper by a mobile transport machine, conveniently a truck-based tipper 330. The mobile biomass stacker 175 moves the soil from the hopper onto the top of dry stack 180, continuously adding fresh soil to the top of the stack, growing the soil cover at the soil’s natural angle of repose, until the base of the soil cover on top of the dry stack 180 extends between the edges or ends 174a and 174b of the BSF storage pad 174. The soil cover is sufficiently thick and continuous to cover all of the material - in particular chunked and dried logs, twigs and branches etc. - of the dry stack 180. The soil cover is built up to a desired thickness, conveniently between about 300mm and about 1000mm, for example 500m. The soil cover thickness selected is preferably based on the soil properties in terms of hydraulic conductivity etc. That is, the selected thickness should be sufficient to prevent moisture permeation into the dry stack 180.

[0107] Biomass stacker 175 moves laterally around the dry stack 180, directing soil towards the centre of the dry stack 180 incrementally from all sides until all of the stacked biomass is covered in soil and the biomass is not visible.

[0108] An alternative method of depositing soil cover layer 182 onto the stack is to use a FEL to dump the soil onto the biomass and a FEL I tractor / push up blade similar to that described above to push and spread the soil cover layer 182. Alternatively, an excavator equipped with a hydraulic grab could be used to place and smooth the soil cover on top of the dry stack 180.

[0109] An alternative to using a soil cover layer 182 to cover the woody biomass prior to the installation of the impermeable plastic membrane is to deposit and spread chipped biomass onto the dry stack 180. The chipped biomass is desirably comprised of 5mm and 25mm pieces and ideally around 15mm pieces, and is conveniently sourced from the smaller pieces of the same dried biomass that is deposited onto the BSF storage pad 174. A conventional industrial scale wood chipper may be directed at right angles towards the dry stack 180 so that a stream of biomass chips hits the dry stack 180 more or less at right angles. The wood chipper is moved, as necessary, to ensure that the layer of biomass chips builds up evenly to cover protruding large pieces of biomass that could damage the impermeable plastic membrane.

[0110] In one embodiment, the soil cover layer 182, is covered with a plastic membrane 182. In this embodiment, once the dry stack 180 is covered in soil, the biomass stack 180 can either be covered in a strong plastic (HDPE, PPE, PVC or similar) membrane cover to provide roof protection of the dry stack 180 from rainfall. Alternatively, the dry stack 180 could be covered in another layer of soil, compactable to form a low hydraulic conductivity soil horizon capable of providing protection of the dry stack 180 from rainfall.

[0111] Once the plastic cover is installed, more soil is stacked in a further soil layer on top of the plastic membrane 182 - as described above - to ensure that the plastic membrane 182 is not exposed to sunlight which would cause deterioration of the plastic over time. The further soil layer is prepared to prevent erosion over time. The further soil layer can be compacted, as described below, or planted with suitable plants. One suitable class of plants includes hardy, relatively shallow rooted locally adapted plants such as saltbush or other locally adapted hardy grasses to mitigate soil erosion.

[0112] Another embodiment does not utilise a plastic membrane. In this embodiment, another layer of soil is added to the dry stack 180 similar to the further soil layer described above. This further soil layer is again of selected thickness to cover and protect biomass held within dry stack 180. For example, the soil layer may have about twice the average thickness of the earlier described layer, for example about 1 m in thickness, a thickness selected to avoid moisture permeation into the dry stack 180. In selecting thickness, regard may be had to the hydraulic conductivity of the soil.

[0113] In either embodiment, once the BSF storage pad 174 is covered in stacked biomass and the stacked biomass is in turn covered in soil, the soil is compacted to as close to optimal compaction as possible via achieving an optimal soil moisture content - as close to 14 wt% moisture as practical for the soils described above and application of mechanical forces to achieve optimal compaction. Exemplary modes of compaction are described in the Applicant’s International Publication No. WO 2024229516 incorporated herein by reference.

[0114] In this manner, the whole of soil cover layer 182 of the dry stack 180 is optimally compacted as indicated in Figure 5. The compacted soil cover layer 182 may then be further covered in another layer of soil which may be planted with hardly relatively shallow rooted locally adapted plants such as saltbush or other locally adapted hardy grasses to mitigate soil erosion.

[0115] At this point, the construction of the BSF storage pad 174 and dried dry stack 180 and cover 182 is complete and is ready for the operation of ongoing, long term monitoring including biomass sampling and analysis, exhaust gas sampling and analysis, and visual inspections as required to demonstrate that zero or near zero captured and sequestered CO2 returns to the atmosphere, and thus verify the effectiveness of the carbon dioxide sequestration system 100 in long term capture and sequestration of atmospheric carbon dioxide desirably as recognised by carbon accreditation agencies.

[0116] Long term monitoring of the condition of the sequestered dried biomass and the identification of early warning signs of biomass degradation or decomposition, by monitoring and measurement system 400, allowing for prompt and efficient remedial action is necessary and beneficial, directly contributing to an independent verification and validation that the biomass captured CO2 is effectively sequestered in accordance with accepted carbon accounting principles. Long term monitoring also evidences direct capture of carbon dioxide from atmospheric air as described below.

[0117] The monitoring and measurement system 400 desirably includes multielement gas and moisture sensors capable of measuring the concentration of O2, CO2, CO (with desirable minimum detection limits of 0.5%) and CH4 (with a minimum detection limit of 2 ppm) temperature and relative humidity. Such sensors are installed to sample exhaust gases from within the dry stack 180 prior to their exit from the vertical exhaust ventilation shaft(s) 187. The 3D position (x-y-z coordinates or polar coordinates) within the dry stack 180 of each gas and moisture sensor is recorded. Anomalous concentrations of any organic gases, temperature or humidity readings indicate that the dried biomass is not being preserved as anticipated or is at risk of degrading or decomposing. The most likely root cause of organic gas emanations will be moist biomass. Spatially registered gas analysis data as described above is used and crosschecked with temperature and humidity readings to target and find any breaches in the protective roof structure or other causes of biomass decomposition, and to implement remedial actions to address the root cause of biomass decomposition.

[0118] The monitoring and measurement system 400 including long-run biomass sampling and TOC analysis data (required for issue of carbon credits or CDRs) also allows measurement of direct capture of carbon dioxide from atmospheric air, drawn into dry stack 180 by ventilation system 184, due to its absorption into, or adsorption onto the surface of cellulose or CNC within the stored dried woody biomass. Cellulose is a linearpolysaccharide molecule having a chain structure consisting of repeating glucose units rich in hydroxyl groups as shown below:

[0119] Without wishing to be bound by theory, carbon dioxide is absorbed into, or adsorbed onto the surface of, woody cellulose at the hydroxyl sites within the above cellulose chain of woody biomass stored in dry stack 180. The stronger electronegativity of the central carbon atom of the linear CO2 molecule creates two dipoles within the molecule, with the oxygen ends of the molecule being positive, when the CO2 molecule is in close proximity to the negative hydrogen end dipole of the hydroxyl group located on the margin of the cellulose chain, the positive oxygen end of the CO2 molecule is attracted to an ultimately bound to the hydroxyl group. The CO2 to hydroxyl bond is called a Hydrogen Bond (Fig. 12) The ball and stick cellulose molecular structure of cellulose 113 has been described, for example, in Nishiyama et al., Crystal Structure and Hydrogen- Bonding System in Cellulose 1 [3 from Synchrotron X-ray and Neutron Fiber Diffraction,the contents of which are hereby incorporated herein by reference.

[0120] The ability of free CO2 molecules to permeate cellulose pores, and macrofibrils and microfibrils thererof, and to interact with, and bond to, the hydroxyl groups on the margins of the cellulose chains of the microfibrils, and to be effectively absorbed or adsorbed is related to the effective gas porosity of the woody biomass material. A very low moisture content, achieved by drying as described above, creates cellulose (and CNC) pores which are not filled in part or in whole by water molecules, and are open to atmospheric gas ingress, allowing for CO2 absorption or adsorption, and CO2 removal from the atmosphere and sequestration, as described above. Increasing the porosity of woody biomass (and cellulose) with further dehydration during storage exposes more hydroxyl bearing cellulose (and CNC) surface area increasing carbon dioxide absorption or adsorption. Lignin and hemicellulose also have hydroxyl groups on their margins capable of hydrogen bonding free CO2 molecules, in the same way asdescribed for cellulose, and may also adsorb or absorb some CO2 but to a lesser extent than cellulose and CNC due to their lower porosity.

[0121] Statistical analyses were conducted to identify any trend in dried biomass TOC over time of Dry Stack storage. The following statistical test was used to test the hypothesis:• Test 1 : A test of the TOC data for (i) dried and stored Eucalyptus wood from dried biomass stack 180 for first half of trial period and (ii) dried and stored Eucalyptus wood from dried biomass stack 180 for second half of trial period.

[0122] The test was conducted to determine if there is a significant difference between the datasets or if each dataset could be considered as being from the same population. In each test, a standard two-tailed T-test of the relevant data for the TOC sample mean (with unpaired data and with a critical p-value of 0.05). Following conventional practice in statistics, the null hypothesis in each case was taken to be that the two populations from which the samples are drawn have the same mean.

[0123] Test 1 TOC data of dried wood was separately pooled for the first half and second half of the trial period to ascertain if there was any statistical difference in wood TOC solely during biomass storage in dry stack 180.

[0124] Test results are set out in Table 1 below:Table 1 : Statistical analysis summary of Demonstration Dry Stack biomass TOC dataTOC being measured as wt% of the biomass.

[0125] Test 1 tested the behaviour of dried wood solely during the biomass stack 180 (‘Dry Stack’) storage process. The mean TOC of the longer stored dried wood is greater than the TOC mean of the shorter stored dried wood, thus the data including p values less than 0.05, supports rejection of the null hypothesis. The two dried wood TOC populations cannot be treated as being the same, there being a statistically significant difference in the sample means. Statistically, duration of biomass stack 180 storage duration increases Eucalyptus wood TOC as shown in Figure 8 showing dried biomassTOC results over time (TOC wt% on y axis and days since stack closure on x axis) showing a statistically valid (r2=0.48) trend to higher TOC values over time.

[0126] The above test shows that carbon sequestered in the stored biomass is not being lost. Analytical error being excluded as a cause of the variation, the cause of the variation was hypothesised to be due to direct capture of carbon dioxide from the atmospheric air drawn through dry stack 180 by the ventilation system 184. The atmospheric air drawn through dry stack 180 contained 420 ppm carbon dioxide.

[0127] Studies of natural wood based cellulose have identified relatively low carbon dioxide absorption or adsorption capacity and limited carbon dioxide absorption or adsorption efficiency. However, wood based cellulose has a porous structure providing a large surface area which allows for carbon dioxide migration, absorption or adsorption and capture as illustrated in the scanning electronic microscope images (a) to (d) of Figure 9 for Eucalyptus grandis, also exemplary of other Eucalyptus species.

[0128] Without wishing to be bound by theory, the hydroxyl groups act as hydrogen bond carbon dioxide absorption or adsorption sites. In particular, cellulose Nano Crystals (CNC) within the cellulose are characterised by extremely large surface areas and high density of hydroxyl groups (Ho, N and Leo, C, A review on the emerging applications of cellulose, cellulose derivatives and nanocellulose in carbon capture, Environmental Research, 197, June 2021 , 111100) and play an important role in carbon dioxide absorption or adsorption. Eucalyptus cellulose is a rich source of CNC. For example, hydrolysed pinewood pulp (treated with 62 wt% H2SO4, 44°C, 90 min) yields 2.3 wt% CNC whereas hydrolysed Eucalyptus pulp (treated with 58 wt% H2SO4, 56°C, 180 min) yields 68 wt% CNC (Kumar, P et al, Nanocrystalline cellulose derived from spruce wood: Influence of process parameters, International Journal of Biological Macromolecules, 221 , 425-434, (2022). It seems probable that the relative abundance of CNC in Eucalyptus cellulose contributes to its carbon dioxide absorption or adsorption ability.

[0129] The potential of the wood based cellulose or CNC to absorb or adsorb and capture carbon dioxide is ultimately related to its effective gas porosity. The higher the moisture content of the wood, the more water molecules fill the cellulose pores and the less gas - here atmospheric air - is able to enter the pores and react with the cellulose or CNC surface. Where, as in preferred embodiments, dryland woody biomass is dried and stored in biomass stack(s) 180 located in climate zones where annual evaporationgreatly exceeds annual precipitation, harvested woody biomass may be naturally dehydrated to very low moisture levels (and consequential higher porosities) as shown in Figure 10 (r2=0.29).

[0130] Woody biomass that enters the system 100 should be weighed and representatively sampled and analysed for moisture content and Total Organic Carbon (TOC). This is conveniently done as biomass is deposited on the storage pad 174. Further, biomass that is dried and stored in the system 100 is representatively sampled and analysed over time for moisture content and TOC. Sampling of biomass within the dry stack 180 after deposition and dry stack 180 closure to further storage of woody biomass is conducted on a regular basis, desirably around every 30 days and for a sufficient period of time, for example at least around 1 year, to demonstrate woody biomass preservation (also referred to as ‘biomass inert’ conditions) has been established and maintained with little to no loss of total organic carbon (TOC) and little to no return of CO2 to the atmosphere. The selected sampling time interval and period of the sampling campaign will vary according to TOC results, greater variability requiring shorter time intervals and a longer sampling campaign to demonstrate woody biomass preservation as a basis for issue of carbon credits or CDRs on the basis of inert, stable, permanent bonding of CO2 to the cellulose and CNC of the woody biomass. In this regard, 1 tonne of captured and sequestered CO2 equates to 1 Carbon Dioxide Removal (CDR) carbon credit.

[0131] All TOC analyses are on a bone dry basis by the Dumas process or similar. In embodiments, the total amount of carbon captured from the atmosphere in the fresh biomass is determined by multiplying the weight of the fresh biomass by its TOC content (on a bone dry basis). The total amount of carbon sequestered in the dried biomass may be determined by multiplying the weight of the fresh biomass by the TOC content (on a bone dry basis) of the dried biomass. The dried biomass is desirably multiply sampled: (i) spatially, in that each ventilation shaft is randomly and systematically sampled and (ii) temporally, in that there are a number of rounds of sampling over time.

[0132] Each load of dried biomass delivered to the BSF is conveniently weighed via on board load cells or a drive on weighbridge. The weight of the load is recorded and matched to a sample of the load. Each load of dried biomass delivered to the BSF is representatively sampled, in a fashion similar to that employed for the delivery of grain to a commercial storage facility. Each load is independently sampled, labelled anddespatched for laboratory analysis. Load sampling density may vary, but should be sufficient to ensure an adequate sampling density for statistically significant measurement and analysis of the sample population.

[0133] Dried biomass is representatively sampled as it is deposited and stacked onto the BSF storage pad 174. This sampling may be continuous sampling of the flow of biomass being moved and stacked (as described above) and / or it could be sampling of the dry stack 180 as it grows. The dried biomass sampling density may vary but should be sufficient to ensure an adequate sampling density and acceptable statistical significance for measurement and analysis of the sample population.

[0134] In preferred embodiments, dried and stacked biomass is representatively sampled once it is stacked via sampling doors of the ventilation shaft(s) 187 as described in the Applicant’s International Publication No. WO 202429516, incorporated herein by reference. The dried and stacked biomass spatial sampling density may vary but should be sufficient to ensure an adequate sampling density and acceptable statistical significance for measurement and analysis of the sampled dry stack 180. The stacked biomass is also desirably sampled via a series of sampling rounds over time after the stack is established. Early sampling rounds are relatively closely spaced, no more than 30 days apart and ideally around 14 days apart. Later sampling rounds are further spaced apart no more than 5 years apart and ideally around 12 months apart. The dried and stacked biomass temporal sampling density may vary but should be sufficient to ensure an adequate sampling density and acceptable statistical significance for measurement and analysis of the sampled biomass stack and ultimately determination of long term carbon preservation within the dried stacked biomass.

[0135] The simplicity of the biomass delivery, drying, moving and stacking system and the efficient access to the stack for on-going sampling allows for ready, independent sampling analysis and verification and validation of the atmospheric CO2 effectively sequestered in the dried stacked biomass, in accordance with established carbon accounting principles.

[0136] Key advantages of the direct absorption into, or adsorption of CO2 onto the surface of cellulose or CNC or woody biomass is that it removes and sequesters extra CO2 from the atmosphere, on top of the CO2 captured and sequestered via photosynthesis during the growth of the source tree, as organic molecules forming the key components of woody biomass’ cellulose, hemi cellulose, lignin and non-structuralcarbohydrates. The system for direct CO2 absorption or adsorption and sequestration described herein effectively delivers simple, cost-effective, large-scale, readily-monitored and verified, direct from the atmosphere Carbon Dioxide Removal (CDR) and carbon sequestration from stored biomass including through absorption / adsorption onto, or into, cellulose and CNC as indicated by Fig. 11 and the above description.

[0137] The system advantageously increases the affordability, availability, and measurability of CDR certificates, allowing for an increase in uptake of CDR, lower atmospheric CO2 levels and a correspondingly decreased atmospheric warming. Further, the system for biomass carbon dioxide sequestration described herein may utilise marginal land unable or difficult to support agriculture or natural biodiversity and / or low- productivity farming land.

[0138] Those skilled in the art will appreciate that the system and method for direct biomass carbon dioxide sequestration described herein is susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps, features, formulations and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

[0139] The invention described herein may include one or more range of values (e.g moisture composition below EMC, dimensions, concentrations etc). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range which lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range.

[0140] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

[0141] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

CLAIMS1. A system for biomass carbon dioxide sequestration from woody biomass comprising:(a) a harvesting module for harvesting or collecting woody biomass;(b) a drying module to which woody biomass assessed to have moisture content greater than a threshold moisture content by weight, is directed from the harvesting module for drying said harvested woody biomass to a dry state where the dried harvested biomass has less than EMC by weight; and(c) a storage module for storing and maintaining harvested dried woody biomass at moisture content by weight less than EMC, wherein said storage module communicates with a gaseous source of carbon dioxide enabling absorption or adsorption of carbon dioxide from the gaseous source onto, or into, the surface of cellulose or CNC contained within the stored harvested woody biomass as said carbon dioxide bearing gas flows through the stored dried, woody biomass.

2. The system of claim 1 , wherein said source of carbon dioxide containing gas is atmospheric air.

3. The system of claim 2, further comprising a ventilation system for circulation of said atmospheric air through the stored dried woody biomass.

4. The system of any one of the preceding claims, further comprising a monitoring system for the generation of biomass and exhaust gas compositional data to measure direct capture of carbon dioxide due to absorption into, or adsorption onto the surface of cellulose or CNC5. The system of any one of the preceding claims, wherein carbon dioxide absorption into, or adsorption onto cellulose or CNC contained within the stored dried woody biomass increases as its porosity increases as a function of dehydration.

6. The system of any one of the preceding claims, wherein hydroxyl groups of cellulose or CNC act as hydrogen bonding carbon dioxide absorption or adsorption sites.

7. The system of any one of the preceding claims, wherein biomass is harvested according to its cellulose or CNC content for use as feedstock.

8. The system of claim 7, wherein said biomass is a Eucalyptus species.

9. A method for carbon dioxide sequestration from woody biomass comprising:(a) harvesting or collecting woody biomass for carbon sequestration purposes(b) drying said harvested woody biomass where harvested woody biomass prior to drying, is assessed to have moisture content greater than EMC by weight so that the dried harvested biomass has less than EMC by weight;(c) storing and maintaining said dried harvested biomass at less than EMC by weight;(d) communicating said stored dried harvested biomass with a gaseous source of carbon dioxide;(e) capturing carbon dioxide from the gaseous source of carbon dioxide by absorption into, or adsorption of carbon dioxide onto, the surface of cellulose or CNC contained within said stored dried woody biomass as said gaseous source of carbon dioxide flows through the stored dried woody biomass; and(f) generating and analysing data to calculate net CO2 removed from the source of carbon dioxide containing gas and sequestered within the dried woody biomass.

10. The method of claim 9, further comprising data generation and analysis thereof, for measuring and quantifying direct capture of carbon dioxide due to absorption or adsorption onto cellulose.11 . The method of claim 9 or 10, wherein carbon dioxide absorption into, or adsorption onto, the surface of cellulose or CNC contained within the stored dried woody biomass increases as its porosity increases as a function of dehydration.

12. The method of any one of claims 9 to 11 , wherein hydroxyl groups of cellulose or CNC act as hydrogen bond sites for carbon dioxide absorption or adsorption.

13. The method of any one of claims 9 to 12, wherein woody biomass is harvested according to its cellulose or CNC content to allow for its utilisation within the invention.

14. The method of claim 13, wherein said harvested biomass is a Eucalyptus species.

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