Ethanol Produced from Perennial Grass Could Offset 20% of Gas Use with 9.3% of Cropland
For all the talk of switchgrass being the next miracle biofuel feedstock, there's still precious little to show for it. Yes, we did recently report on a study which showed that switchgrass could potentially yield 5 times more energy than was used to grow it and, yes, there are several companies that are working hard to bring cellulosic ethanol to market. Yet, for all its purported merits, we aren't likely to see it become commercially available for another few years.
Scientists from the University of Illinois at Urbana Champaign have just staged the largest known field trial for Miscanthus, a giant perennial grass. Their results indicate that using Miscanthus as an ethanol feedstock could significantly boost biofuel production in the U.S. while greatly reducing the acreage devoted to them.
Offsetting 20% of gas use with 9.3% of agricultural land
According to Stephen Long, a professor of crop sciences at UIUC, it would be possible to produce enough cellulosic ethanol with 9.3% of agricultural land to offset a fifth of our current gasoline consumption. By comparison, it would take 25% of current cropland to produce an equivalent amount of corn-based ethanol. Similar field trials conducted for switchgrass were disappointing: producing roughly the same amount of ethanol per acre as corn -- a result that glaringly contradicts the results I cited above.
A longer growing season and superior photosynthetic efficiency contribute to Miscanthus' high yield
The two principal reasons why Miscanthus yields more ethanol per acre than corn, Long explains, are that it makes green leaves 6 weeks earlier in the growing season and keeps them until late October. Corn leaves typically wither by the end of August. While it shares a similar growing season, switchgrass is much less efficient at photosynthesis; Miscanthus has a conversion efficiency of around 1% (1% of sunlight gets turned into biomass).
Like many perennial grasses, Miscanthus can be grown in poor quality soil and can store a lot of carbon dioxide -- making it close to carbon neutral. Growing it wasn't an easy process, Long says. Because it is sterile, Long and his colleagues had to plant rhizomes, its underground stems, which took a long time. Once they got it going, however, they found that it provided returns annually without having to be replanted.
Miscanthus: "still in its infancy"
As Long readily admits, Miscanthus still has a ways to go before it becomes a viable alternative to gas, let alone corn ethanol:
Keep in mind that this Miscanthus is completely unimproved, so if we were to do the sorts of things that we’ve managed to do with corn, where we’ve increased its yield threefold over the last 50 years, then it’s not unreal to think that we could use even less than 10 percent of the available agricultural land. And if you can actually grow it on non-cropland that would be even better.
More about switchgrass and other grasses
::Planting Switchgrass Could Improve Soil Quality
::Switchgrass Yields Five Times More Energy Than is Used to Grow it
::TreeHugger Picks: Far-Out Fuels for the Future