Method and system for processing a biomass for producing biofuels and other products

Abstract

The present invention provides methods of processing a biomass, e.g., for producing lipid and non-lipid materials, by inducing autolysis of a biomass. The biomass may be generated using any species of microorganism and any available biodegradable substrate, including waste materials. The lipid and non-lipid materials are present in two separate layers of the autolysate, and they can be used to generate valuable products such as biofuels and nutritional supplements. The present invention further provides a processing apparatus useful for practicing the methods of the present invention.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61 / 223,995 filed Jul. 8, 2009, where this provisional application is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to methods of processing a biomass to obtain useful lipid and non-lipid materials, including intermediates for producing biodiesel and ethanol. In particular embodiments, a microorganism is grown on a biodegradable substrate and the resulting biomass is induced to undergo autolysis, thus releasing the lipid and non-lipid materials from the biomass. The present invention is also directed to a processing system useful for practicing the methods of the present invention.[0004]2. Description of the Related Art[0005]The global energy crisis is continuing to grow as fossil fuels are facing their inevitable depletion. At the sa...

AI Technical Summary

Benefits of technology

[0058]As described above, one advantage of the present invention is that the microorganisms used to produce lipid and non-lipid materials may be grown on a wide variety of inexpensive and readily available biodegradable substrates. A “biodegradable substrate” or “substrate” as used herein refers to any material that can be consumed and / or degraded (e.g., aerobic or anaerobic degradation) by a microorganism. The biodegradable substrate may be inanimate or living (e.g., parasites). The biodegradable substrate may be a liquid or a solid, and it may be inorganic or organic. In certain preferred embodiments, the biodegradable substrate is waste or a byproduct. Preferably, but not necessarily, the substrate possesses a high energy density.

[0059]Examples of solid biodegradable substrates include, but are not limited to, cellulosic waste materials, farming, agricultural, and landscaping waste (e.g., non-edible portions of plants, leaves, stems, branches, flowers, seeds, clippings, husks, mulch, and manure), solid municipal waste (e.g., household and commercial waste, such as paper, cardboard, yard and food waste), calcium carbonate (e.g., limestone, eggshells, and shells of marine organisms), coal (e.g., peat, anthracite, and graphite), and parasites (e.g., nematodes, cestodes, trematodes, and protozoa).

[0060]Examples of liquid biodegradable substrates include, but are not limited to, liquid municipal waste (e.g., household and commercial waste, such as wastewater and sewage), non-potable water, urine, blood and other bodily fluids (e.g., slaughterhouse waste), silage, industrial organic waste, dairy farming waste, fruit and vegetable washing water, cooling water (e.g., water used in iron and steel production), mining slurry, sludge, and crude oil and derivatives (e.g., petroleum, motor oil, and lubricants). Aqueous substrates may contain saltwater or freshwater.

[0061]Since any available biodegradable substrate may be used, the substrate does not need to be transported long distances, if at all. Unlike the production of first and second generation biofuels, the feedstock material, i.e., the biodegradable substrate, can be utilized at or near its source. Furthermore, the final products, the lipid and non-lipid materials obtained from the autolysate, can be generated in close proximity to or at the site of the substrate to reduce costs for transportation and distribution of the newly obtained materials.

[0062]In addition, new feedstock sources, such as crops, do not need to be generated and harvested to begin the process, e.g., when the substrate is a waste material. Furthermore, the generation of fuel and other valuable products from waste material reduces the global need for waste removal and storage, such as municipal landfills. Since there are biodegradable materials and microorganisms all over the world, the wide availability of alternative fuels will not be a problem using the present methods as is the case with first and second generation biofuels. Furthermore, the present invention will eliminate problems associated with the reliance on fossil fuel sources. Using the methods of the present invention, the dependency will shift to a reliance on globally available and abundant materials to produce biofuels.Microorganisms

[0063]A wide variety of different microorganisms may be used according to the methods of the present invention. In particular embodiments, the microorganism used may be selected based upon its ability to degrade a desired substrate. For example, brown rot fungi are capable of consuming cellulose and hemicellulose; white rot fungi are capable of consuming lignocellulose; and Saccharomyces cerevisiae and Zymomonas mobilis are capable of consuming glucose. Information regarding the ability of various microorganisms to consume or degrade particular biodegradable substrates is available in the art.

Problems solved by technology

The global energy crisis is continuing to grow as fossil fuels are facing their inevitable depletion.

Substituting biofuels for fossil fuels will decrease the greenhouse effect, and with a steady, sustainable, and uninterrupted supply, biofuels will not be a finite fuel source.

However, liquid biofuels generated thus far have their own difficulties and concerns that need to be addressed and overcome.

Therefore, first generation biofuels compete with human and animal nutrition for agricultural crops, because these crops are produced on a limited amount of land.

This limited amount of farm land cannot satisfy both global food and fuel needs, thereby generating the food vs. fuel conflict.

Accordingly, first generation biofuels are limited by competition with food crops for land and cannot be abundant enough to become widely available, thus preventing the adoption of alternative fuels.

In addition, algae consume the greenhouse gas carbon dioxide and produce the globally needed oxygen as a metabolic waste product.

However, the selection of lignocellulose and algae as starting materials introduced a new set of problems.

In particular, generating ethanol from lignocellulose has a number of technical problems.

Delignification of lignocellulose to liberate cellulose and hemicellulose from their complex with lignin is the rate-limiting and most challenging step in the production of ethanol from lignocellulose (Lin and Tanaka.

In addition, depolymerization of the carbohydrate polymers (e.g., acid hydrolysis of the cellulose from wood) destroys most of the desired materials, simple fermentable sugars, in the process.

Also, the fermentation of hexose and pentose sugars together generates a low ethanol yield.

Hydrolysis of lignocellulose feedstock via high temperatures, acid treatment, and / or high pressure is also a complex energy consuming process.

In addition to, and due in part to, the technical problems of generating lignocellulosic ethanol, its production cost is high despite the fact that lignocellulose is an inexpensive agricultural residue when compared to the starch-based agricultural products used in the production of first generation biofuels.

Also, the costly initial investment to convert or build a lignocellulose refinery would result in a small number of lignocellulose refineries, high freight costs for delivering bulky cellulose long distances to the limited number of refineries, very large and costly storage areas to contain the biomass, and a large output of residual waste.

The high cost of lignocellulosic ethanol, the drastic drop in oil prices at the end of 2008, and the global economic crisis contributed in putting many lignocellulosic ethanol projects on hold and leading to a reluctance to invest in ethanol projects.

Additionally, since the mid-1970s, extensive research has been carried out in the field of lignocellulosic ethanol production; however, the first lignocellulosic ethanol fuel plant was not operational until 2004 in Canada.

Although the lipids derived from algae are readily converted to biodiesel by known methods, and lipid extraction via oilseed extraction is available (see, e.g., U.S. Pat. No. 4,456,556), the cultivation of algae is challenging.

For example, growing algae in an open-pond system is much less expensive than growing algae in a closed photobioreactor system; however, the open-pond system is open to contaminants, and it is more difficult to provide optimal amounts of carbon dioxide and light while maintaining the temperature and pH to achieve maximum growth of the algae in an open-pond.

Thus, stimulating exponential growth of algae in a closed or open system is costly, and cultivating algae on a commercial scale is exceedingly difficult.

Bioreactors have proven to be most effective in producing high quality algae at the greatest rate, but they are expensive, and it has yet to be shown that algae are economically feasible for commercial scale production (see, e.g., Benemann, Opportunities and Challenges in Algae Biofuels Production [online], [Retrieved on Jun. 22, 2009].

Images