5 Promising Biofuel Feedstocks Roundup

Genetically engineered microorganisms

The other big innovation in biofuel technology has been the growing use of genetically engineered bacteria to convert renewable feedstocks -- fermenting their sugars -- into hydrocarbon-based fuels meant to mimic conventional gasoline (without all the excess baggage). Like most new technologies, this one still has a way to go before it's ready for the big time, but the companies involved, including Codexis, Amyris Biotechnologies, LS9 and Craig Venter's Synthetic Genomics (which wants to turn CO2 into biofuel), are making progress and have had some good initial results.

Miscanthus, switchgrass and other perennial grasses

Switchgrass may not be the miracle feedstock that many once thought it would become, but it, alongside Miscanthus and a variety of exotically named grasses (bermudagrass and napiergrass, to name a few), has still been the recipient of plenty of hype of late. Their appeal is two-fold: They are plentiful and can be grown easily, and they would not displace agricultural food production because they can be grown on unused marginal lands.

A recent study done by researchers from the University of Illinois found that 9.3% of the nation's agricultural land could be used to produce enough Miscanthus-based cellulosic ethanol to offset a fifth of our current gasoline consumption. Though the same study concluded that switchgrass would only produce as much ethanol per acre as corn, an earlier study done by University of Nebraska researchers showed that switchgrass grown on marginal lands could yield 540% more energy than is used to grow it.

Speaking of which, Tennessee and DuPont just broke ground on a major new research refinery, part of the state's $70 million "Grassoline" initiative, to turn waste biomass and switchgrass into commercially-viable cellulosic ethanol.

Other studies have shown the appeal of planting polycultures of multiple grass, prairie and wildflower species as an alternative to switchgrass or Miscanthus monocultures. David Tilman and his colleagues at the University of Minnesota found that these mixed plantations produced twice as much biomass and produced a form of biofuel that could store 51% more energy per acre than corn. Another plus: these crops could be carbon negative -- that is, they could sequester more carbon dioxide than they produce.

Trash and municipal waste

Last, but certainly not least, trash (of all feedstocks) has become another popular alternative to corn and other food-based crops. It's hard to think of a more ideal feedstock -- being both (extremely) cheap and readily available -- than landfill waste, though it remains to be seen how expensive (and practical) the production process will be. (To be clear, these waste-to-ethanol facilities are not to be confused with the more conventional waste-to-energy facilities, which generate electricity from burning trash and have been around for years.)

Edmonton, Canada, and Reno, Nevada, will soon be the homes of the world's first industrial-scale waste-to-ethanol plants. The $70 million Canadian facility, to be jointly developed by Greenfield Ethanol and Enerkem, will initially produce roughly 36 million liters of biofuel a year. Reno's $120 million plant, which will be built by Fulcrum BioEnergy, is expected to begin operations in 2010 and will generate about 10.5 million gallons a year from 90,000 tons of waste.

As you can tell from this list, even some of the most promising feedstocks still have a ways to go before they'll be ready for prime time -- if they even get there, of course. (For what it's worth, I'd cast my vote for algal biodiesel.) Some are further along than others, but only time will tell whether one or the other will successfully make the transition from research lab to gas station.