Grass biofuels 'cut CO2 by 94%' - BBC

[Eugene]

Source: BBC News

Last Updated: Tuesday, 8 January 2008, 12:05 GMT

Grass biofuels 'cut CO2 by 94%'

Producing biofuels from a fast-growing grass delivers
vast savings of carbon dioxide emissions compared with
petrol, a large-scale study has suggested.

A team of US researchers also found that switchgrass-

derived ethanol produced 540% more energy than was
required to manufacture the fuel.

One acre (0.4 hectares) of the grassland could, on
average, deliver 320 barrels of bioethanol, they added.

Their paper appears in the Proceedings of the National
Academy of Sciences.

-snip-

Read more: http://news.bbc.co.uk/2/hi/science/nature/7175397.stm

[GliderGuider]

1. The article doesn't say what production technology they assumed in their ethanol estimates

However, he added that as there were no large-scale biorefineries in operation, the team did have to estimate how much bioethanol such a plant would be able to produce in order to calculate the net energy gain.

"Right now, the Department of Energy is co-funding the construction of six biorefineries in the US. These plants will be completed around 2010, and will be above the pilot plant scale."

[OKIsItJustMe]

2. It would have to be "cellulosic ethanol"

http://www.jgi.doe.gov/education/bioenergy/bioenergy_11.html

... Switchgrass, which grows naturally in most of the U.S., has the potential to produce the biomass required for the production of up to 100 gallons of ethanol per metric ton. This high yield makes it an attractive crop because its value exceeds any other crop. The challenge lies in efficient conversion—burning switchgrass yields 14.6-fold more energy than the input required to produce it; converting switchgrass to ethanol consumes 45% more energy than produced.

...

http://www.eia.doe.gov/oiaf/analysispaper/biomass.html

...

Assuming the development of cost-effective production facilities, cellulosic biomass feedstocks like switchgrass, agricultural residues, and hybrid poplar trees could supply a growing ethanol industry with large quantities of less expensive raw materials. To differentiate the current use of corn with the future use of cellulosic biomass and the differences in production technology, corn is generally characterized as a “first generation” energy crop, whereas switchgrass and other cellulosic materials are “second generation” energy crops.

...

[OKIsItJustMe]

3. Here's the study: Net energy of cellulosic ethanol from switchgrass

http://www.pnas.org/cgi/content/abstract/0704767105v1

Net energy of cellulosic ethanol from switchgrass

M. R. Schmer*, K. P. Vogel*,†, R. B. Mitchell*, and R. K. Perrin‡

*U.S. Department of Agriculture–Agricultural Research Service, University of Nebraska, 314 Biochemistry Hall, P.O. Box 830737, Lincoln, NE 68583-0737; and ‡Agricultural Economics Department, University of Nebraska, 314A Filley Hall, Lincoln, NE 68583-0922

Edited by Pamela A. Matson, Stanford University, Stanford, CA, and approved November 21, 2007 (received for review May 21, 2007)

Abstract

Perennial herbaceous plants such as switchgrass (Panicum virgatum L.) are being evaluated as cellulosic bioenergy crops. Two major concerns have been the net energy efficiency and economic feasibility of switchgrass and similar crops. All previous energy analyses have been based on data from research plots (<5 m²) and estimated inputs. We managed switchgrass as a biomass energy crop in field trials of 3–9 ha (1 ha = 10,000 m²) on marginal cropland on 10 farms across a wide precipitation and temperature gradient in the midcontinental U.S. to determine net energy and economic costs based on known farm inputs and harvested yields. In this report, we summarize the agricultural energy input costs, biomass yield, estimated ethanol output, greenhouse gas emissions, and net energy results. Annual biomass yields of established fields averaged 5.2 -11.1 Mg·ha^–1 with a resulting average estimated net energy yield (NEY) of 60 GJ·ha^–1·y^–1. Switchgrass produced 540% more renewable than nonrenewable energy consumed. Switchgrass monocultures managed for high yield produced 93% more biomass yield and an equivalent estimated NEY than previous estimates from human-made prairies that received low agricultural inputs. Estimated average greenhouse gas (GHG) emissions from cellulosic ethanol derived from switchgrass were 94% lower than estimated GHG from gasoline. This is a baseline study that represents the genetic material and agronomic technology available for switchgrass production in 2000 and 2001, when the fields were planted. Improved genetics and agronomics may further enhance energy sustainability and biofuel yield of switchgrass.

Full Study: http://www.pnas.org/cgi/reprint/0704767105v1.pdf

... A hydrolysis/fermentation biorefinery was the model cellulosic ethanol plant for EBAMM, with cogeneration power/export being the average of a steam Rankine cycle power system and a gas turbine combined cycle system (9, 44). ...

[jwirr]

4. back in the 70s we were all excited about the issue of "land use".

That is what it comes down to now - maybe even more. Until they come up with a bio fuel product that will BOTH efficiently feed the world and provide fuel there will be a conflict. However, if we are self-centered about it then we can convert lawns into switch grass instead of gardens.