Scientific American
By George W. Huber and Bruce E. Dale
July 2009 edition
www.scientificamerican.com

Key Concepts

* Second-generation bio­fuels made from the inedible parts of plants are the most environmentally friendly and technologically promising near-term alternatives to oil.

* Most of this “grassoline” will come from agricultural residues such as cornstalks, weedlike energy crops and wood waste.

* The U.S. can grow enough of these feedstocks to replace about half the country’s total consumption of oil without affecting food supplies.


Scientists are turning agricultural leftovers, wood and fast-growing grasses into a huge variety of biofuels—even jet fuel. But before these next-generation biofuels go mainstream, they have to compete with oil at $60 a barrel

By now it ought to be clear that the U.S. must get off oil. We can no longer afford the dangers that our dependence on petroleum poses for our national security, our economic security or our environmental security. Yet civilization is not about to stop moving, and so we must invent a new way to power the world’s transportation fleet. Cellulosic biofuels—liquid fuels made from inedible parts of plants—offer the most environmentally attractive and technologically feasible near-term alternative to oil.

Biofuels can be made from anything that is, or ever was, a plant. First-generation biofuels derive from edible biomass, primarily corn and soybeans (in the U.S.) and sugarcane (in Brazil). They are the low-hanging fruits in a forest of possible biofuels, given that the technology to convert these feedstocks into fuels already exists (180 refineries currently process corn into ethanol in the U.S.). Yet first-generation biofuels are not a long-term solution. There is simply not enough available farmland to provide more than about 10 percent of developed countries’ liquid-fuel needs with first-generation biofuels. The additional crop demand raises the price of animal feed and thus makes some food items more expensive—though not nearly as much as the media hysteria last year would indicate. And once the total emissions of growing, harvesting and processing corn are factored into the ledger, it becomes clear that first-generation biofuels are not as environmentally friendly as we would like them to be.

Second-generation biofuels made from cellulosic material—colloquially, “grassoline”—can avoid these pitfalls. Grassoline can be made from dozens, if not hundreds, of sources: from wood residues such as sawdust and construction debris, to agricultural residues such as cornstalks and wheat straw, to “energy crops”—fast-growing grasses and woody materials that are grown expressly to serve as feedstocks for grassoline. The feedstocks are cheap (about $10 to $40 per barrel of oil energy equivalent), abundant and do not interfere with food production. Most energy crops can grow on marginal lands that would not otherwise be used as farmland. Some, such as the short-rotation willow coppice, will decontaminate soil that has been polluted with wastewater or heavy metals as it grows.

Huge amounts of cellulosic biomass can be sustainably harvested to produce fuel. According to a study by the U.S. Department of Agriculture and the Department of Energy, the U.S. can produce at least 1.3 billion dry tons of cellulosic biomass every year without decreasing the amount of biomass available for our food, animal feed or exports…

The full article can be read at Scientific American Magazineclick here