Switchgrass Yields Five Times More Energy Than is Used to Grow it
by Jeremy Elton Jacquot, Los Angeles on 01. 8.08
We may have been a bit rash in dismissing the prospects for switchgrass out of hand a few months back. A new study by the University of Nebraska's Kenneth Vogel has shown that switchgrass, a prairie grass found alongside the borders of many fields, yields 540% more energy than is used to grow it.
Vogel and his colleagues conducted the first large-scale field study of switchgrass by monitoring its growth on the borders of 10 farms in Dakota; they noted the amount of seed, fertilizer and fuel used, the amount of precipitation and the amount of grass harvested over the span of 5 years. Using data from corn ethanol plant technologies and smaller-scale switchgrass conversion studies, Vogel estimated that an average of 60 GJ per hectare could be obtained if the switchgrass were converted into bioethanol.
That impressive 540% figure compares quite favorably to the 93% return on soybean biodiesel and (measly) 25% return on corn ethanol. Emissions produced from using switchgrass bioethanol would be roughly 94% lower than those from gasoline - making it almost carbon neutral.
One of switchgrass' many benefits, Vogel explains, is that it need not take up valuable space that would otherwise be used to grow food crops; it is perfectly happy being grown on marginal cropland. The grass only needs to be planted once - after which it will provide year on returns - and has an intricate underground root system that can lock carbon in the soil. That's not to say that switchgrass lacks its own set of potential issues.
Rainer Zah at the Swiss Materials Science and Technology research institution faults current estimates for not taking into account the global warming effects of dinitrogen oxide, a very potent GHG produced during the cultivation of switchgrass. “The technology to make full use of all the carbon in switchgrass is not yet established,” said Zah, pointing out that it may yet be a while before the energy yield Vogel obtained could be replicated on an industrial scale.
While Vogel acknowledges that it will be difficult to set up "large-scale field trials . . . particularly for an extended period of time in a large geographical area,” he believes the 540% figure could be increased further with better land management and breeding techniques and with improvements in cellulosic ethanol production technologies.
Via ::Nature News: Prairie grass energy boost studied in the field (news website)
See also: ::Wired on "The Plant That Will Save America", ::Are Switchgrass' Days Numbered?, ::Bait and Switchgrass
Image courtesy of Doctor Swan via flickr
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Brilliant. While the use of any biofuel is a step foward from using straight petroleum products, the conclusion from this study is very promising. Being able to yeild so much energy and nearly closing the carbon loop makes it worth serious investigation.
I thought the issue was that the grass was pretty much impossible to get rid of, which means no crop rotation and poor soil management. It grows too fast to give other plants a chance and eliminates bio-diversity. If we want to talk about energy yields, let's not forget palm oil in the warmer climates. It gets a bad rap because a-holes clear cut land to plant it. But the plant is very useful.
Growing is just one step in the process - let's not forget that. To make it a fuel, it will be grown (possibly with pesticides and genetic modification?), harvested (using tractors?), shipped to a plant (by truck?), converted to fuel (other inputs?), shipped (by truck?) and then used by the consumer. Each step there uses enegy in one or more forms, so just becuase it can yield 540% the energy that it takes to grow it, the total energy usage isn't quite so simple.
Better than oil? Maybe.
If it can be done using only biofuel instead of petrolum in all these steps, than it's a viable option.
So...
Shipping grass from Kansas uses more energy than shipping oil from Saudi Arabia?
please, let's not skip the plant which grows the fastest on this planet (all things considered) - hemp aka cannabis sativa.. not only does its seed give oil for fuel/etc., but the same crop also provides an excellent food source, and extremely useful fiber for paper/construction etc..
At 7100kg/ha they found in the study, and their assumed 0.38L/kg, it would 632,755 square miles to replace fuel 2005's U.S. Vehicle Miles Traveled (2.7 trillion) assuming the 2020 CAFE standards of 35 MPG. (Of course in 2020, VMT will be much higher.) In contrast, it would take only 3,607 square miles of Concentrated Solar Power to fuel the same VMT in 300 Wh/mi battery electric vehicles (such vehicles were designed and produced in the 1990s--not new technology). 632,755 or 3,607 square miles: which would you choose?
So, it only requires an area the size of Texas to grow enough grass to make that fuel?
'Marginal cropland' can also be called 'ecosystem' and 'habitat'. Better think about the impacts of enlarging planted areas. Such as the Dust Bowl.
It would also be more appropriate to express the net energy production value of the entire process, rather than the gross figure. Therefore: Switchgrass can potentially provide 4.4 times as much energy as that invested in its production. This is still an impressive value, though tiny compared to the energy return on investment of conventional petroleum fields.
To all, we are engaged in a project to grow the stuff, pelletize it on site or at a local pellet plant and burn it for fuel in pellet stoves/furnaces. In fact we have already done this in Middeltown, NY (awaiting grant$$ while going broke). IT WORKS NOW-TODAY-RIGHT HERE!!! The technology to produce the pellets EXISTS NOW-RIGHT HERE- READY TO GO.
We heat our 8000 sq ft pellet factory with pellet power - no oil, no gas - we got heat!!! Check out the USDA Lower Hudson Valley RC&D of NY - Hudson Valley Grass Energy Collaborative- Cornell Coop is working on the cellulosic side of this equation, we work the burn part. It's all good!!!! SYracuse University students are working on the self generation part of the stove equation - create you own electricty to power your pellet stove on locally grown fuels.
What's not to like?
MiniMills saved the American steel industry by localising it. Small localised switchgrass power stations can do the same for the America energy industry. No need to transport switchgrass a long way (like oil). It's much more efficient to take it to a small local converter and let the utility transport the energy as electricity.
Unlike Europe, most land in America is unused; it grows nothing but grass. Spend half the corn subsidy on switchgrass energy, and we can make this wasteland profitable (and forget Alaskan oil). Spend the rest on improving switchgrass yields and we can forget Canadian oil shale (and Saudi Arabia). Arable farmers will make money from marginal land, and we get energy security, stop burning fossilised CO2, and stop raising food costs. Win-win-win really.
Why isn't Amoco racing to become Amsco? Where are the venture capitalists?
MiniMills saved the American steel industry by localising it. Small localised switchgrass power stations can do the same for the America energy industry. No need to transport switchgrass a long way (like oil). It's much more efficient to take it to a small local converter and let the utility transport the energy as electricity.
Unlike Europe, most land in America is unused; it grows nothing but grass. Spend half the corn subsidy on switchgrass energy, and we can make this wasteland profitable (and forget Alaskan oil). Spend the rest on improving switchgrass yields and we can forget Canadian oil shale (and Saudi Arabia). Arable farmers will make money from marginal land, and we get energy security, stop burning fossilised CO2, and stop raising food costs. Win-win-win really.
Why isn't Amoco racing to become Amsco? Where are the venture capitalists?