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Monday, February 7, 2011

All biofuels not created equal

Efforts to replace fossil fuels with renewable energy are proceeding on two parallel tracks. Solar, wind and other technologies are being deployed to generate grid-connected electricity (instead of coal or natural gas) while biofuels are being developed to replace petroleum-based transportation fuels.

In addition to concerns about (net) greenhouse gas emissions, biofuels have also attracted support from those who want to reduce U.S. imports of foreign oil.

Biofuels are thus one of the major research areas of the U.S. Department of Energy and its National Renewable Energy Laboratory. A 2006 NREL brochure summarizes the various alternatives.

Two major types of biofuels are being developed — alcohol and biodiesel — to replace petroleum-based gasoline and diesel respectively. (For safety reasons, efforts to test jet fuel replacements have so far used blends of regular jet fuel and biodiesel.)

While next-generation alcohol fuels are under development, the current generation fuels are mainly ethanol. The most widely used (and most controversial) biofuel in the US is corn-based ethanol, which is sold today at many gas stations as a 10% (soon 15%) blend with conventional gasoline.

Ethanol is a grain-based alcohol that has numerous disadvantages when compared to gasoline. It has lower heat content, is miscible with water and highly corrosive. However, for more than a decade, some “FlexFuel” cars have been designed to run with (and resist corrosion from) E85, i.e. 85% ethanol. My 2000 Ford pickup says it is compatible with E85, although I’ve never seen it for sale here in California.

Corn-based ethanol also poses economic challenges. After the U.S., the second largest producer of ethanol is Brazil, which refines its ethanol from sugar cane. Brazil’s ethanol industry is pushing for trade sanctions against the U.S. over our net 99¢ subsidy for use of domestic over imported ethanol. Because ethanol consumes one-third to 40% of American corn, some also blame it for the recent increase in food prices.

Cellulosic ethanol offers a way to overcome these food vs. fuel problems, because it uses crop residue, grasses and other organic material that do not require prime farmland. However, these feedstocks pose greater technological problems in processing to produce fermentable sugars. To overcome these challenges, cellulosic ethanol is attracting hundreds of millions of dollars in government and industry investment to develop commercial-scale bioprocessing facilities.

Broadly, there are also two categories of feedstocks for biodiesel. One category includes the existing oilseed crops — such as canola, jatropha or palm oil — which were used in some of the earliest bio-jet fuel experiments two years ago. Indigenous to the Sonoran Desert, varieties of jatropha have become a popular fuelstock for growing in arid areas such as the U.S. Southwest, Africa or India.

The second category of biodiesels are algal biofuels. Microalgae can be grown in non-arable land — or even saline or brackish water — and produce a higher concentration of oil than more the complex oilseed plants. They also can be genetically engineered (or selected) for characteristics best suited for fuel production.

Both forms of biodiesel still require manufacturing process improvements necessary to build commercial refineries of scale and efficiency comparable to decades-old petroleum-based technologies. The microalgae approach also requires additional research into developing (or screening) and then cultivating the most suitable strains.

In California, San Diego has become the state’s (if not the nation’s) hub for algae-based biofuels, with two major firms as well as the San Diego Center for Algae Biotechnology, a large university-industry research center headquartered at UCSD. Venture investors, the Federal government, and even oil companies like ExxonMobil have bet heavily on the future prospects for algal biofuels.

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