Switchgrass

The president raised the point that switchgrass might be in our future as a source for cellulosic ethanol.  There were also some questions raised on my previous fortuitous post "New Ethanol Study". Most of this post is a combination of direct quotes from the two resources listed at the end.

Switchgrass is a native of North America where it occurs naturally from 55º N latitude to deep into Mexico, mostly as a prairie grass. In North America it has long been used for soil conservation and as a fodder crop. Both in America and Europe it can be found as an ornamental plant. The grass is also found in South America and Africa where it is used as a forage crop. Switchgrass is a perennial C4 grass propagated by seed that can be established at low cost and risk and requires very low inputs while giving high biomass yields even on marginal soils. Since the early 1990s the crop has been developed as a model herbaceous energy crop for ethanol and electricity production in the USA and in Canada and it is also being considered as a paper pulp production feedstock.

First, a distinction: switchgrass and your suburban lawn grasses—bluegrass and zoysia grass— are about as similar as a shopping-mall ficus and an old-growth redwood. Switchgrass is big and it's tough—after a good growing season, it can stand 10 feet high, with stems as thick and strong as hardwood pencils.

But what makes switchgrass bad for barefoot lawns makes it ideal for energy crops: It grows fast, capturing lots of solar energy and turning it into lots of chemical energy— cellulose—that can be liquified, gasified, or burned directly. It also reaches deep into the soil for water, and uses the water it finds very efficiently. And because it spent millions of years evolving to thrive in climates and growing conditions spanning much of the nation, switchgrass is remarkably adaptable.

Many farmers already grow switchgrass, either as forage for livestock or as a ground cover, to control erosion. Cultivating switchgrass as an energy crop instead would require only minor changes in how it's managed and when it's harvested. Switchgrass can be cut and baled with conventional mowers and balers. And it's a hardy, adaptable perennial, so once it's established in a field, it can be harvested as a cash crop, either annually or semiannually, for 10 years or more before replanting is needed. And because it has multiple uses—as an ethanol feedstock, as forage, as ground cover—a farmer who plants switchgrass can be confident knowing that a switchgrass crop will be put to good use.

Annual cultivation of many agricultural crops depletes the soil's organic matter, steadily reducing fertility. But switchgrass adds organic matter—the plants extend nearly as far below ground as above. And with its network of stems and roots, switchgrass holds onto soil even in winter to prevent erosion.

Nitrogen management is an important component of any non-leguminous cropping system, but it is particularly important for bioenergy systems as nitrogen is an important cost energetically, economically and, potentially ecologically, as a contributor to air and stream pollution. "Standard" practices for switchgrass have called for £50 kg of N during the first year after switchgrass emergence, followed by 80–100 kg/ha thereafter (Wolf and Fiske 1995). Research has included these and much higher rates in the search for an optimum balance between costs and yield. To date positive yield responses have been found up to and including 224 kg N/ha-year, however it is  suspected that long term yield stability and economics will be favored by lower annual or even longer interval applications of N, particularly where a single annual harvest is used.

Data analyses are not yet complete, however, early indications are that much lower N levels can be applied once stands are fully developed. This can be attributed in part to the level of root growth and the accumulation of soil carbon under perennial grasses as noted in studies in the Soil Conservation Program.

As with most plant systems, root production in the surface soils is a predominant feature of switchgrass development and VPI studies indicate that approximately 50% and 75% of switchgrass roots in the top 90 cm of soil can be found in the top 15 cm and 30 cm of the soil profile, respectively. We have analyzed soil carbon gains in the surface horizons across a total of 13 research plots to date to document anticipated increases associated with root turnover and mineralization by switchgrass. These include measurements made after the first 3 years of cultivation in Texas, and after 5 years of cultivation in plots in Virginia and surrounding states. Preliminary analyses indicate that carbon gains will be comparable to, or greater than the 1.1 MgC/ha-year gains reported for perennial grasses, which included switchgrass, in studies in the Conservation Reserve Program (Gebhart et al. 1994). Additional studies are ongoing to document gains across deeper profiles and to standardize measurement protocols and minimize sampling variability across sites.

The issue of soil carbon gains and carbon turnover rates has become one of particular importance to energy crops for several reasons. First, soil carbon is well recognized as an extremely important determinant of soil fertility, as it controls both water and nutrient retention and lightens the texture of soils thereby promoting aeration, drainage of excess water, and root growth (Reeves 1997). This is an important issue because energy crops have the potential to improve the quality of agricultural soils depleted by decades of poor cropping management (McLaughlin et al. 1994). In this capacity they qualify as appropriate vegetative cover for fulfilling the soil conservation objectives of the Conservation Reserve Program

Besides helping slow runoff and anchor soil, switchgrass can also filter runoff from fields planted with traditional row crops. Buffer strips of switchgrass, planted along streambanks and around wetlands, could remove soil particles, pesticides, and fertilizer residues from surface water before it reaches groundwater or streams—and could also provide energy.

Among the 19 research sites in the Eastern and Central United States raising switchgrass for the BFDP studies, Bransby's site holds the one-year record at 15 tons per acre. Those are dry tons weighed after all the moisture's been baked out. Convert that into ethanol, an alcohol that can fuel vehicles, and it equals about 1,500 gallons per acre. Bransby's 6-year average, 11.5 tons a year, translates into about 1,150 gallons of ethanol per acre. An added bonus is the electricity that can be produced from the leftover portions of the crop that won't convert to ethanol.

Seed establishment makes switchgrass a very attractive biomass crop since it is inexpensive and reduces financial risks. Experiments have shown that no-till establishment methods are suitable for switchgrass. Spring establishment dates and seeding rates were tested indicating that as low as 200 Pure live seeds per square meter can be sufficient for establishing a good stand. Further development of establishment methods for specific regions and soil conditions (slopes) is possible to decrease establishment risk and cost. 

Because switchgrass allocates so much energy to root establishment, stands typically are not harvested during the first growing season, reach 2/3 of their capacity during the second year and full yield potential by the third year.

The Bioenergy Feedstock Development Program (BFDP) at Oak Ridge National Laboratory has been conducting research for the Department of Energy since 1978 to identify and develop fast growing trees and herbaceous crops as well as to evaluate the potential crop residues as sources of renewable energy the nation's future energy needs.

Resources:

References mentioned in this post are found in the references section of my second resource.

Biofuels from Switchgrass: Greener Energy Pastures, Prepared for ORNL, produced by DOE EERE Office of Transportation Technologies
Developing Switchgrass as a Bioenergy Crop, Biofuels Systems Division of the U.S. Department of Energy, under contract No. DE-ACO5-96OR22464 with Lockheed Martin Energy Research Corp.

Technorati tags: biofuels, switchgrass, energy, technology

Comments

[Rod Adams]

What are some of the effects on the soil when harvesting switchgrass? Can it keep growing year after year if intensively harvested?

[Engineer-Poet]

FTFA:

once it's established in a field, it can be harvested as a cash crop, either annually or semiannually, for 10 years or more before replanting is needed.

[BOG]

Could ahigh sugar content switch grass be bio-engineered?

[Jim from The Energy Blog]

BOG - In the second resource that I listed there is a discussion of some work being done to breed higher yielding strains of swithgrass. As I understand the paper, work has started on bio-engineering, but it is in the early stages and research is needed to understand the DNA, genetics (?) of switchgrass before any actual bio-engineering can begin. I believe that attempts to improve the sugar content could be made once these parameters are understood. - I am not the one to ask about bio-engineering or what can be done with it. This program has had relatively low funding for the past ~6 years so not much progress has been made.

[Jay Custin]

While I certainly see the advantages of using a harvested crop for fuel sources as opposed to fossil fuels, I am curious on how the net profit per acre compares to other more problematic crops such as tobacco. I have no clue on what all the costs, etc. are in crop production, but I am curious if there would be sufficient incentive for the average tobacco farmer to convert (incrementally or outright) from that crop to switchgrass. Obviously the latter has the benefit of producing crops that not only reduce the farmer's dependence on tobacco (IMO a good thing) but also might make widespread of this E85 fuel feasible. I have to laugh at the blanket advertising of E85 on television in the last few weeks seeing as I have never seen an E85 station in NC or VA.

My other thought is how effectively switchgrass could be used to suppliment hog and poulty (maybe even cattle) farms while helping to reduce the contamination of the surrounding estuaries.

[testersup]

to find a sation near you that sells ethanol go to www.e85fuel.com/index.php
in NC charlotte has three,shelby has two,statesville has one,and arlington VA has one. ethanol will become more abundant in the future. there are alot of distillers being built they take a long as a year to build.

[Castor Oil]

From what I read here, switchgrass appears to be perhaps the most attractive feedstock for ethanol production (1) it is not used as a edible crop while sugarcane/corn etc are used as edible crops, (2) its yield appears to be higher per acre than for many other ethanol feedstock, and (3) it appears that it could be energy positive, though I know more work needs to be done on this aspect

What I am wondering is, why is the US govt clamouring about ethanol from corn while I hear very little about switchgrass? Perhaps I will hear more about it from now one, hopefully

Castor, Biodiesel from Algae

[amazingdrx]

The problem is that fuel farming with chemical agriculture destroys the soil as a carbon sink, vastly increasing the severity of global climate change.

Except for fuel from algae in solar collectors, I think it's a winning techology.

[Brian McCreary]

Jim,Brian here. I was thinking about the farming here in N. Florida. Cotton, soy beans and peanuts. I was wondering if the foliage from these plants would make good cellulosic methanol. Most of it seems to go to waste.Another thing I don't understand, they take used cooking oil and turn into bio-diesel when adding alcohol and lye. Why couldn't you cook the whole plant and get the oil and the methanol already mixed ? Thanks,Brian

[Debbie Anglin]

For all those interested in more information on Switchgrass: The Governor of Oklahoma will host GROW: the Governor's Conference on Biofuels, October 16-17, 2007 in Oklahoma City. Switchgrass and other native Oklahoma prairie grasses show great potential for alternative fuels. James woolsey, former director of the CIA, will be a keynote speaker at this year's conference. Registration is only $45. For more information or registration, visit www.GrowOK.com

[averagejoe]

If switchgrass could serve as a feedstock for Butanol production, then they'd really have something. Also, planting a mixture of native prairie grasses probably makes more sense that using monoculture. By planting a nitrogen fixing grass along with the switchgrass, they could reduce or eliminate fertilizer inputs.

[averagejoe]

Correction: I should have said: "By sowing a nitrogen fixing plant, of some kind, along with the switchgrass..." Not being a farmer, I don't know if there are nitrogen fixing species of Grass. Clover, vetch, and legumes in general all fix atmospheric nitrogen, but I'm not sure if they fall into the category of grasses. Perhaps someone more knowledgable could comment on native prairie plants that fix nitrogen.

[valeriy]

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