(226b) Development of a Sustainable Microalgal Biofuels Industry: Of Ponds, Promises and Prospects

As petroleum supplies diminish, the United States becomes increasingly dependent upon crude oil from unstable regions of the world. The United States currently imports more than 60% of its petroleum. Of that, 2/3 is used for the production of transportation fuels as amounting to 140 billion gallons per year (gal yr-1) of gasoline and 44 billion gal yr-1 of on-road diesel. Soaring energy demand in developing nations is beginning to create intense competition for the world's limited petroleum resources. In addition, the combustion of fossil fuels has created serious concern about global greenhouse gas (GHG) accumulation and its effects on world economies and human habitat. In response to these global concerns, the 2007 Energy Independence and Security Act (EISA) contains provisions designed to increase the availability of renewable energy that decreases GHG emissions while at the same time establishing a very aggressive Renewable Fuels Standard (RFS). This RFS calls for the production of 36 billion gallons of renewable fuels by 2022 of which at least 21 billion gallons must be advanced biofuels (i.e., non-corn ethanol). Cellulosic ethanol is expected to play a large role in meeting the EISA goal for advanced biofuels, but ethanol is largely designed to address the world gasoline markets. There is also an equally important need for the development of higher energy density biofuels. Although there are a number of processes under development to produce high energy density biofuels from lignocellulosic biomass, the amount of biomass that can be produced in a sustainable fashion annually is estimated to be approximately 1 billion tons which could replace at most only about 50% of our transportation fuels. Taking both the need for high energy density fuels and the limitations in terrestrial biomass production into consideration, many energy analysts are becoming increasingly interested in the promise of biofuels derived from microalgal biomass.

Oil-rich, microalgae are technically viable and attractive alternatives which could contribute significantly to our goal of energy independence. There are several aspects of algal biofuel production that have combined to capture the interest of researchers and entrepreneurs around the world. These include: 1) High per-acre productivity, 2) Algal feedstock based on non-food resource, 3) Use of otherwise non-productive, non-arable land, 4) Utilization of a wide variety of water sources (fresh, brackish, saline, and wastewater), 5) Potential to mitigate GHG release into the atmosphere; and 6) Production of both biofuels and valuable co-products.

A comprehensive research and development program for the development of algal biofuels was initiated by the US Department of Energy (DOE) more than 30 years ago. The DOE-supported Aquatic Species Program (ASP) at the National Renewable Energy Laboratory (NREL) illustrated the potential of algae to provide liquid energy. Despite the substantial progress made during the almost 18 year duration of the ASP in such areas as strain collection and screening, biochemistry and physiology of lipid accumulation, genetic engineering of algae and large-scale continuous cultivation of algae in outdoor raceway ponds, the program was discontinued in 1996 because of decreasing federal budgets and a lack of national will to pursue biofuels in the face of low petroleum costs.

Much has changed since the end of the ASP, especially the dramatic growth of the biotech industry including the development of sophisticated systems biology tools as well as opportunities for the incorporation of lower cost materials in the construction of photobioreactors. What hasn't changed until quite recently is a recognition that algal biofuels could play an important role in our energy economy. Between 1996 and 2006, a dearth of federal support for algal R&D, resulted in little growth in scientific progress as well as little growth in the algae technical community. In the last few years, however, interest in the commercialization of algal biotechnology has virtually exploded, with the appearance of nearly 200 new startup companies on the scene focused on various aspects of algal biofuels and co-products. In addition, the Department of Defense (DoD) through its Defense Advanced Research Projects Agency (DARPA) and Air Force Office of Scientific Research (AFOSR) activities has made some significant research investments in the development of algal feedstocks for biojet fuel production.

DOE's intention to explore the appropriate mechanism to support algal biofuel research and to accelerate progress towards commercialization was revealed in December, 2008 when, the DOE Office of Energy Efficiency and Renewable Energy (EERE), Office of the Biomass Program (OBP), held the first ever Algal Biofuels Technology Roadmap Workshop. This two day event involved more than 200 scientists, engineers, research managers, industry representatives, academics, lawyers, financiers and regulators in a series of breakout sessions designed to identify barriers to production of algal biofuels at a significant scale. The topics covered included: algal biology, cultivation, harvest/dewatering, extraction/fractionation, conversion to fuels, co?products, technoeconomic analysis of algal biofuel production, systems integration, siting & resources, and regulation and policy. The roadmap document based upon the output from the workshop is expected to be released during the latter part of 2009.

All of the elements for the production of lipid-based fuels from algae have been demonstrated. Algae can be grown in large outdoor cultures and harvested. The algal lipids can be extracted and converted to transportation fuels. The relevant question is not whether biofuels from algae are possible, but rather whether they can be made economically and at a scale sufficient to help contribute to U.S. fuel demand. There are, however, a number of major technical challenges that will need to be overcome to achieve this goal. Significant attention and support should be given to both basic and applied research on algae for biofuels applications and the engineering of sustainable microalgal systems. Preliminary technoeconomic analysis indicates that algal productivity is one of the primary production cost determinants and so efforts should be focused on various aspects of algal biology that can have the greatest impact on growth rate and lipid biosynthesis. However, this work cannot be done in isolation, and it would be a mistake to equate progress in productivity made at the bench scale with success in large scale cultivation, and so attention must also be paid to growth under conditions that model commercial production (including climate, and input sources), with data exchanged between biologists and process engineers. In anticipation of success of this revolutionary approach to a novel 21st century concept of agriculture, using land that has never been developed for any purpose, it will also be essential to complete a detailed life cycle analysis (LCA) and ecological impact analysis in advance of large scale deployment to ensure a smooth path to commercialization. An LCA should also include a very detailed assessment of the energy recoveries for algal biofuels production (i.e., net energy being recovered in the algal fuel compared to energy input from fossil fuels in order to produce the renewable fuels). Based on recently published energy calculations microalgal biofuels do have the potential to be produced sustainably.

This plenary lecture on algal biofuels development will provide a brief overview of the potential of microalgal biofuels production, past algal research sponsored by DOE, the current status of the technology development and a discussion of the technical and economic barriers that need to be overcome before production of microalgal-derived diesel fuel substitutes can become a large-scale commercial reality.