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April 23, 2014  |  Login
Biofuel Salad Bar
By John Rubino

Assuming at least one of the many experimental processes works-and indications are that several will-the next step is to choose a biomass to turn into tomorrow's black gold. There are several leading contenders:

Switchgrass Here's a bit of irony: When Europeans arrived in the United States and began migrating westward, they eventually came to the Great Plains, hundreds of miles of rolling hills and tall grasses. Deeming the grasses useless, they proceeded to plow them under to plant corn, wheat, and soy and paved the rest for highways and subdivisions. The grasses were relegated to the periphery of the farm economy or pockets of wild land. But now, as factory farms and suburbs drain the world of oil and natural gas, those grasses are getting a second look, and they're turning out to be one of the things that might save the factory farm and suburban lifestyle from extinction.

Take switchgrass, a big ugly plant that gets prettier the more you learn about it. One of the dominant grasses on the old Great Plains, it grows fast, can reach 10 feet in height, needs relatively little water, and can thrive in a wide range of environments and soils. A few farmers already grow it, either as forage for livestock or as ground cover to control erosion (its roots extend nearly as far below ground as its stalks grow above, which holds soil in place). It can be cut and bailed like hay using existing combines. And it's a hardy, adaptable perennial, so once established in a field, it can be harvested annually or semiannually for 10 years or more before replanting is needed. And because it has multiple uses-as ethanol feedstock, forage, and ground cover-a farmer who plants switchgrass knows he'll find a use for it.

Experimental switchgrass plots are yielding enough to make 1,000 gallons of ethanol annually per acre. And what isn't used to make ethanol can be burned to generate energy to run the process. Early results indicate that switchgrass can produce ethanol equal to about five times the energy required to obtain it. That's far better than corn. Switchgrass also removes considerably more CO2 from the air than corn, sequestering it in its roots. In short, switchgrass has a lot of theoretical promise as an energy crop, and we'll soon find out if reality matches theory. Massachusetts-based Mascoma, a start-up formed to commercialize the research of Dartmouth professor and biofuel pioneer Lee Lynd, recently raised $60 million to build several plants, including one in Tennessee that will use specially designed microorganisms to covert switchgrass to ethanol. Production is slated to begin in 2009.

Forest Waste The lumber business doesn't use anything close to the whole tree. Branches and bark are left on the forest floor during logging and sawdust and wood chips on the sawmill floor during processing. Figure out how to turn this wood into energy, and you've got a free feedstock that doesn't require synthetic fertilizer, usurps no farmland, and doesn't disturb the price of any other commodity. That's the rationale behind a Georgia biomass-to-fuel plant being built by Colorado-based Range Fuels. Range employs "a two-step thermo-chemical process" to produce cellulosic ethanol from pine chips and other waste from local softwood logging operations. Soon the verdict will be in on whether this process lives up to billing, but the early claims are impressive. Range-which has the enthusiastic backing of major clean-tech venture capitalist Vinod Khosla, among others-describes the process as "self-sustaining, with virtually no waste products, very low levels of greenhouse gases, and high yields of clean ethanol."

Other Plant and Industrial Waste California-based BlueFire Ethanol now operates several facilities in Japan that coat things like urban trash and wheat straw with sulfuric acid to free up the cellulose, and turn the resulting sugars into ethanol. more

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