Is Alfalfa 'Green' Fuel of the Future?

This forage, in second year of seeding, beats out switchgrass.

Published on: Mar 9, 2007

If alfalfa became a biomass ethanol crop, would it be billed as the ultimate "green" fuel? What would you call it, "alfalfanol"?

Alfalfa has a lot of potential as an energy feedstock for cellulosic ethanol production, according to Neal Martin, director of USDA's Dairy Forage Research Center in Madison, Wis. Martin was interviewed at the Mid-America Alfalfa Expo in Kearney.

As a total crop, corn still offers the best ethanol yield if the grain, leaves and stalks were all used for ethanol production, according to recent calculations. Switchgrass is second. Alfalfa is a close third, under a system by which the leaves would be removed for feed before processing the stems into ethanol.

But in the second year, alfalfa moves ahead of switchgrass because unlike either of the other crops, alfalfa does not need nitrogen fertilizer to grow. It makes its own.

Alfalfa is a good crop for biomass ethanol production for several reasons, says Martin: It doesn't need nitrogen applications like corn or switchgrass and it doesn't need seeding annually like corn. Alfalfa ground can provide a yield boost for corn when it is planted after alfalfa.

The knowledge of how to best grow and harvest alfalfa is already in practice.

Alfalfa provides good soil erosion protection during the off-season.

Martin says the USDA Agricultural Research Service's Plant Science Development Unit in St. Paul, Minn., and the University of Minnesota are working to develop a biomass-type alfalfa that would grow taller without lodging. The biomass type is grown at a less-dense seeding rate than forage alfalfa and is harvested only twice during the growing season.

Leaf yields were similar to forage alfalfa, but stem yields increased 37% and the potential ethanol yield of the stems doubled. Biomass-type alfalfa under a biomass management system would also be beneficial to wildlife, especially nesting birds because it wouldn't need to be harvested so early in the growing season, says Martin.