Algae as a Feedstock for Biofuels: An Assessment of the State of Technology and Opportunities. Final Report
- Sentech, Inc. (United States)
- Independent Consultant (France)
The pursuit of a stable, economically-sound, and environmentally-friendly source of transportation fuel has led to extensive research and development (R&D) efforts focused on the conversion of various feedstocks into biofuels. Some feedstocks, such as sugar cane, corn and woody biomass, are targeted because their structures can be broken down into sugars and fermented into alcohols. Other feedstocks, such as vegetable oils, are appealing because they contain considerable amounts of lipids, which can be extracted and converted into biodiesel or other fuels. While significant R&D and commercial strides have been made with each of these feedstocks, technical and market barriers (e.g., cost, scalability, infrastructure requirements, and 'food vs. fuel' debates) currently limit the penetration of the resultant biofuels into the mainstream. Because of algae's ability to potentially address several of these barriers, its use as a feedstock for biofuels has led to much excitement and initiative within the energy industry. Algae are highly diverse, singleor multi-cellular organisms comprised of mostly lipids, protein, and carbohydrates, which may be used to produce a wide variety of biofuels. Algae offer many competitive advantages over other feedstocks, including: 1) Higher potential lipid content than terrestrial plants, sometimes exceeding 50% of the cell's dry biomass (U.S. DOE, May '10; Tornabene et al., 1983) 2) Rapid growth rates that are 20-30 times higher than terrestrial crops (McDill, 2009) and, in some cases, capable of doubling in size with 10 hours 3) Diverse number of species that can collectively thrive in a wide range of environments throughout the world, presenting an overall high overall tolerance for climate, sunlight, nutrient levels, etc. 4) Daily harvesting potential instead of seasonal harvest periods associated with terrestrial crops 5) Potential to redirect CO2 from industry operations to algal cultivation facilities to be used in an algal biofuel cycle before it is released into the atmosphere 6) Ability to be cultivated on land that that is unsuitable for agriculture, so it does not directly compete with farmland Given microalgae's high lipid content and rapid growth rates, maximum oil yields of 20,000--115,000 L/ha/yr (2,140-13,360 gal/ac/yr) have been estimated. xiv 7) Ability to thrive in seawater, wastewater, or other non-potable sources, so it does not directly compete with fresh water resources. In fact, wastewater can provide algae with some essential nutrients, such as nitrogen, so algae may contribute to cleaning up wastewater streams. 8) Non-toxic and biodegradable 9) Co-products that may present high value in other markets, including nutriceuticals and cosmetics Given microalgae's high lipid content and rapid growth rate, maximum oil yields of 20,000 -- 115,000 liters per hectare per year (L/ha/yr) (2,140 -- 13,360 gallons per acre per year) (Baldos, 2009; Wijffels, 2008) have been estimated, which is considerably higher than any other competing feedstock. Although algae species collectively present many strong advantages (although one specific species is unlikely to possess all of the advantages listed), a sustainable algal biofuel industry is at least one or two decades away from maturity, and no commercial scale operations currently exist. Several barriers must first be overcome before algal biofuels can compete with traditional petroleum-based fuels. Production chains with net energy output need to be identified, and continued R&D is needed to reduce the cost in all segments of the production spectrum (e.g., harvesting, dewatering, extracting of oil). Further research to identify strains with high production rates and/or oil yields may also improve competitiveness within the market. Initiatives to seamlessly integrate algal biofuels into the existing transportation infrastructure may increase their convenience level.
- Research Organization:
- IEA-Advanced Motor Fuels Agreement, Annex 34, Subtask 2 (United States)
- OSTI ID:
- 21580861
- Country of Publication:
- United States
- Language:
- English
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