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Study: Miscanthus More Than Twice as Productive as Switchgrass for Energy Crop

11 July 2007

Miscanthus2
Miscanthus. Standing next to the grass is Dr. Emily Heaton (now with Ceres), who is 5' 4" (163 cm) tall. Source: UIUC

Researchers at the University of Illinois at Urbana-Champaign have made the first direct comparisons of the biomass productivity of two C4 perennial grasses: switchgrass (Panicum virgatum) and  Miscanthus (Miscanthus x giganteus). The two have been widely trialed as low-input bioenergy crops in the US and EU, respectively.

Results from the trials throughout Illinois show that Miscanthus is more than twice as productive as switchgrass. Its efficiency of conversion of sunlight into biomass is amongst the highest ever recorded. The research team presented their results at Plant Biology and Botany 2007, a joint congress including the American Fern Society (AFS); the American Society of Plant Biologists (ASPB); the American Society of Plant Taxonomists (ASPT); and the Botanical Society of America (BSA).

The team, led by Frank Dohleman of the Plant Biology Department, theorized that Miscanthus produces more usable biomass than switchgrass because of these three key attributes:

  1. Miscanthus can gain greater amounts of photosynthetic carbon per unit of leaf area;

  2. Miscanthus has a greater leaf area; and

  3. Miscanthus has a longer growing season.

The research team measured the amount of gas exchanged on the upper canopy of Miscanthus leaves from pre-dawn to post-dusk on 20 dates in the 2005 and 2006 growing seasons. The averages from two years’ data showed that Miscanthus gained 33% more carbon than switchgrass.

Integrated measurements also showed that the Miscanthus leaf area was 45% greater than switchgrass and that Miscanthus plants grew an average of eleven days longer than switchgrass. This extended growing season and accompanying lower temperatures proved to further boost the photosynthetic activity of Miscanthus. Specifically, pyruvate Pi dikinase was found to be expressed at higher rates when ambient temperatures are lower. This enzyme supports C4 photosynthesis in Miscanthus.

The University of Illinois at Urbana-Champaign is working with the University of California at Berkeley and the Lawrence Berkeley National Laboratory in forming the new $500-million Energy Biosciences Institute (EBI) funded by BP, with UC Berkeley taking the lead.  (Earlier post.)

As part of the EBI, some 340 acres of farmland at the Urbana campus will be devoted to the study and production of feedstock for biofuel production. Researchers will explore the potential benefits of using corn crop residues, switchgrass, Miscanthus and other herbaceous perennials as fuel sources. The initiative will explore how adequate supplies of high quality plant biomass can be sustainably produced and utilized in facilities that convert the biomass to fuels.

Feedstock development is one of five research areas at the EBI. The others are biomass depolymerization; fossil fuel bioprocessing (converting heavy hydrocarbons to cleaner fuels) and carbon sequestration; socio-economic systems; and biofuels production. In addition to feedstock development and socio-economic research, Illinois will work with the other research institutions on biofuels production. UC Berkeley will lead this part of the project, with Illinois joining the search for the most efficient use of microbes to harvest the energy in plants for biofuels.

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July 11, 2007 in Biomass, Cellulosic ethanol | Permalink | Comments (35) | TrackBack (0)

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If we're serious about biofuel production, this type of research is essential to maximize feedstock production by given land area.

This could lead to using less food crop land to satisfy essential cellulosic biofuel production.

Coupled with 100 mpg to 200 mpg PHEVs, countries with large land areas like USA, Canada, Brazil, Russia, China, India, Argentina etc., could produce enough biofuel without putting undue pressure on food production.

What are the chances that
A. anyone in the position to do anything will see this
and
B. will actually act on this?

Brad,

When the enzymes and/or pyrolosis techniques are efficient enough to make cellulosic ethanol cost-competitive, then it's all about the feedstocks. Farmers who get paid by the ton will be all over this kind of research. Farmers care about yeild per acre compared to whatever else they could grow on that land.

If Miscanthus can grow on truly marginal lands, that raises a different question; will farmers start cultivating where they did not cultivate before?

What kind of requirements does this stuff have for water and fertilizer?

@ HealthyBreeze -

it might make sense to start separating the discussion about cellulose feedstocks from that of the fuel(s) they are turned into.

Cellulose can be broken down into simple sugars (a mix of mostly glucose and xylose) using a combination of mechanical, thermal and enzymatic processing. Let's call the everything up to this point "upstream" and refer to the intermediate product as say, "c-slush".

All additional processing into fuels or other products should be considered "downstream". The product may be ethanol, n-butanol, dimethylfurane or perhaps something else. The yields for each for the associated processes will differ, as will the properties of the educts as fuel additives and/or substitutes.

It's early days yet in the biofuels sector and, no-one really knows how it's going to play out. So please, let's not get use cellulosic ethanol as shorthand for any and all second-generation biofuels. In particular, the emphasis on ethanol at the expense of the alternatives covers up the fact that it currently enjoys massive subsidies and protectionist tariffs in the US.

Or you can just burn the stuff.

Any chemical conversion of biomass, such as that from Miscanthus, involves significant losses. I believe it would be better to dry and pelletize this biomass and use it for home heating, where you get to use 80% or more of the energy content of the biomass, depending on the efficiency of the pellet-burning furnace. The fuel oil or nat. gas saved could then be used more easily elsewhere, e.g. transportation.

This should represent a much more efficient over all use of resources rather than utilizing only a portion of available biomass and suffering significant losses in the conversion process to make transportation fuels.

Converting biomass into biofuel does more then just fuel cars, it also competes with oil in the industrial market of making solvents, plastic, composites, pharmaceuticals, etc, thus it not as simple as just burn biomass for energy and screw biofuels.

"I believe it would be better to dry and pelletize this biomass and use it for home heating,"

Steve, where would the demand for these pellets come from? You are proposing investments in a whole new infrastructure of pellet-burning furnaces. I understand that this is a technology that exists, but a very low percentage of people have this capability right now? 80% efficiency? That doesn't sound too good for a furnace to me. Where does the rest go?

Most importantly, if implemented correctly, the supply of biomass would almost certainly exceed the demand for these pellets. We need this energy for much more than just home heating. That would not displace enough oil to fix our problems.

I completely agree that the best biofuel output may be n-butanol or a player-to-be-named-later. I also assume there will be a miscanthus equivalent to wet distillers grain or fertilizer, or bagasse that can be burned in cogeneration.

IMO it would be better to burn those pellets at power stations than in homes. The ash and emissions can be more easily minimized and disposed of. There would be no need for new home furnaces. And transportation of the pellets in bulk would be cheaper.

Since I favor nuclear I don't want the stuff burned anyway. Liquid fuel is what we need from biomass for a decade or so.

Ethanol and butanol and lions and tigers and bears... Oh my!!......... Ethanol may not be the best possible gasoline extender or replacement. But for the nation there is some merit in actually getting something into cars within a few years. So I prefer we continue on the ethanol path.

Otherwise I sense there will be thrashing and arguing about various molecules for a decade. If another biomass fuel proves definitively better then phase it after 2015.

I seem to remember a number of different processes that could be used on-site to condense the energy before transporting it to an electrical generating plant for use in EV's. (my personal favourite)

Burning dry biomass for heat and/or electricity production does make a lot of sense. The trouble is the stuff is typically quite wet and doesn't actually burn very well. I suppose the waste heat from the combustion process could be used to dry the next batch and create low-grade feed steam in the process, but I'm not sure if the available enthalpy and/or the heat transfer would be sufficient.

Also, burning biomass not as lucrative as producing automotive or aviation fuels. Besides, at some point we actually will need to wean the essential transportation sector off crude oil - growing miscanthus just to burn it would let us postpone that day, but not indefinitely.

Torrefied biomass can be pelletized, and takes up relatively little water.  It contains about 90% of the energy of the raw dry biomass, but only about 70% of the mass.  Spontaneous combustion may be a problem; I have not been able to learn much about it.

However, one thing needs to be understood:  even Miscanthus Giganticus is not going to replace fossil fuels in legacy systems.  Biological productivity is nowhere near great enough.  Any full solution is going to involve pushing the efficiency of the consuming systems from the ~15% of today's vehicles to more like 70%.

As long as we wait for the private sector to deem this profitable enough, we may be waiting a LONG time.

If as a society we say that our tax dollars should go to THIS instead of war, then we will have bio fuels from coast to coast.

Our choice, wait until we run out of time or take action and avoid a disaster.

To Robert Schwartz
It appears to have relatively low requirements for fertiliser. Though probably needs irrigation to get high yields. There are some interesting agronomic research reports if you google Miscanthus. It is a C4 plant (like sugar cane) but can photosynthesize efficiently over a much wider temperature range and could be used to ameliorate dryland salination (a big problem in Australia's wheat belt). I am concerned about sustainability in monoculture and introduction of exotic plants on native ecology. In Australia for example Jatropha is a declared noxious weed. So although these solutions often look exciting, there are always many issues to consider. The EBI appears to be a very approriate way to assess suitable biomass options. Found a very interesting paper on the biomass economy with respect to Australia's situation.

http://www.cse.csiro.au/publications/1999/biomasseconomy-99-07.pdf

SJC:

The problem with committing tax dollars to one technology or another is that you create a massive special interest--just like the farm subsidies that have created the corn ethanol debacle. Government shouldn't do any more than fund basic R&D, then let engineers and the private sector work out what actually works best economically.

"governments shouldn't do any more than just fund basic R&D, then let engineers and the private sector work out what actually works best economically."

OK. I agree in principle. So why are we carrying massive budget deficits to fund major military efforts to keep stability in the oil exporting regions of the world? Is this not a subsidy to the oil economy? If we're going to discuss energy infrastructure on economic terms, you have to include all of the costs.

Oh, right, we're in Iraq for the Iraqi's sake, I forgot.

Any solution like this is a long-shot, but unless we start placing a lot of 100-1 bets, we're not going to avoid our looming liquid fuel crisis. In light of the risks, a half billion dollars is nothing; we should be making this kind of investment on a weekly basis.

Solve the energy crisis develop domestic sources of oil. Such as Alaska off the coast of Florida and California and other areas currently restricted by overzealous environmental regulations. Develop technology to convert coal to liquid fuel. Build more refiners for oil. Then farmers can grow food.

Farmers grow what returns them a profitable margin on inputs while ensuring long term sustainability of their land. If a farmer can get a better return growing biomass for fuel than getting screwed by a supermarket or commodity trader for food crops he/she will. Miscanthus can be a rotation crop to sequester depleted soil carbon and restore fertility to soil. It has the added advantage of being a fuel source. Pumping more oil from the Arctic or converting coal to liquids doesn't address the problem of CO2 build up and is not a long term sustainable solution to energy supply.

Hey, that picture looks a lot like my back yard when I get behind on the mowing. I wonder if I could plant Miscanthus back there? Where do you get the stuff?

Here's a link to a Wired magazine article about an ethanol plant in Nebraska started by the founder of Sun Microsystems.
"But the single most critical variable in the biohol trajectory is the coming rise in the number of gallons of fuel produced per acre. As we migrate from biomass derived from corn to biomass from so-called energy crops like switchgrass and miscanthus, I estimate that biomass yield will reach 20 to 24 tons per acre, a fourfold increase. At the same time, new technologies will enable us to extract more biohols from every ton of biomass, potentially to 110 gallons per ton. The result: We’ll be extracting 2,000 to 2,700 gallons of fuel per acre (as opposed to about 400 gallons with today’s technology). With better fuels and more-efficient engines improving mileage by about 50 percent, we can safely predict a seven- to tenfold gain in miles driven per acre of land over the next 25 years. Given this biohol trajectory, a future of independence from gasoline becomes not only possible but probable. And the trajectory begins with garden-variety corn ethanol"

http://www.wired.com/wired/archive/14.10/ethanol.html

Energy crisis? What energy crisis? We've got so much oil and gasoline, we're literally drowning in the stuff. Its abundantly available everywhere you look and there's so much, it only costs $3/gal. We have more than we can efficiently use, so we simply waste it in huge, oversize vehicles. It seems like we can't burn the stuff fast enough to get rid of what they pump out of the ground. The last thing we have is an "energy crisis".

Alan,

What planet are you on? Haven't you been reading things like how the IEA and other oil analyses are say that demand will soon or is already exceeding supply?!

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