Ethanol Produced from Perennial Grass Could Offset 20% of Gas Use with 9.3% of Cropland
by Jeremy Elton Jacquot, Los Angeles on 07.31.08
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.
That opening is giving other potential second-generation feedstocks, such as kudzu and cattails, an opportunity to prove their ethanol mettle. Enter Miscanthus giganteus.
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.
Via ::Green Car Congress: Large Field Trial Shows Miscanthus Could Meet US Biofuels Goals With Less Land (news website)
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
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Still makes me wonder why there's no research into converting plain old everyday lawn grass into a fuel source. After all, we already spend billions on lawns and landscaping growing, cutting, and collecting the stuff.
Why bother with these plants when algae give much greater yields of biofuel per acre, with year-round output. I read one report that said that 10% of New Mexico could supply all of the US transport needs. Problem is, there's so much conflicting data out there that one doesn't know what to believe.
I did a little checking around, and I note that Miscanthus is an Asian plant. It doesn't sound like an invasive plant, but is anyone trying to use the native perennial grasses of the tallgrass prairie biome? These plants are already adapted to American soils--in fact, they built them. They have been shown to sequester large amounts of carbon in their roots systems. Given that the tallgrass biome was dependent on regular burns to maintain prairie status, perhaps it would also be amenable to clearcutting for fuel stock harvest. Just a thought.
It seems like everyday we are finding new and even more efficient sources of biofuels like ethanol and inventing ever more effective methods of extracting the energy. Makes me excited as both an environmentalist and someone who's ready to get off of foreign oil.
Michael makes a good point. I wonder why there isn't research into turf grass. if it works we should already have more than enough planted with a welll established municipal collection system.
even if the yield were 10% of other sources the shear volume that's readily available would more than compensate.
The Crop Science Department at North Carolina State University is working with crops natively grown to NC; including switchgrasses. www.cropsci.ncsu.edu
Has anyone noticed "making it close to carbon neutral"? This means that we'd still be pouring CO2 into our atmosphere; not a good idea. We need to forget the internal combustion engine altogether and focus our research on solar, for example.