New Argonne lifecycle analysis of bioethanol pathways finds corn ethanol can reduce GHG emissions relative to gasoline by 19-48%; long-term, cellulosic offers the most benefits

Well-to-wheels results for greenhouse gas emissions in CO2e for six pathways. Source: Wang et al. Click to enlarge.

A new lifecycle analysis of five bioethanol production pathways by a team from Argonne National Laboratory led by Dr. Michael Wang found that, relative to petroleum gasoline, ethanol from corn; sugarcane; corn stover; switchgrass; and miscanthus can reduce lifecycle greenhouse gas (GHG) emissions [P10-P90 (P50)] by 19-48% (34%); 40-62% (51%); 90-103% (96%); 77-97% (88%); and 101-115% (108%), respectively when including land use change emissions. They researchers reported similar trends with regard to fossil energy benefits for the five bioethanol pathways. An open access paper on the study in published in the journal Environmental Research Letters.

While the results for cellulosic ethanol (stover, switchgrass and miscanthus) are in line with recent studies, and the findings for sugarcane ethanol are only slightly lower than other similar studies, the results for corn ethanol are in sharp contrast to other studies predicting that corn ethanol would have a greater life-cycle GHG impact than gasoline, the authors noted.

Bioethanol is the biofuel that is produced and consumed the most globally. The US is the dominant producer of corn-based ethanol, and Brazil is the dominant producer of sugarcane-based ethanol. Advances in technology and the resulting improved productivity in corn and sugarcane farming and ethanol conversion, together with biofuel policies, have contributed to the significantly expanded production of both types of ethanol in the past 20 years. These advances and improvements have helped bioethanol achieve increased energy and GHG emission benefits when compared with those of petroleum gasoline.

-Wang et al.

In the study, the team used an updated, upgraded version of the GREET model (developed at Argonne by Dr. Wang and colleagues) to estimate life-cycle energy consumption and GHG emissions for the five bioethanol production pathways on a consistent basis. The GREET model covers bioethanol production pathways extensively; the team updated key parameters in the target pathways based on recent research.

Even when they included the highly debated land-use change (LUC) GHG emissions, when the feedstock was changed from corn to sugarcane and then to cellulosic biomass, bioethanol's reductions in energy use and GHG emissions, when compared with those of gasoline, increased significantly. Thus, they concluded, in the long term, it is cellulosic ethanol production that will offer the greatest energy and GHG emission benefits.

WTW GHG emission reductions for ethanol pathways relative to gasoline. Values are reductions for P10-P90 (P50), relative to P50 of gasoline GHG.
	Corn	Sugarcane	Corn stover	Switchgrass	Miscanthus
Including LUC emissions	19-48% (34%)	40-62% (51%)	90-103% (96%)	77-97% (88%)	101-115% (108%)
Excluding LUC emissions	29-57% (44%)	66-71% (68%)	89-102% (94%)	79-98% (89%)	88-102% (95%)

They separated GHG emissions into WTP (well-to-pump); PTW (pump-to-wheel); biogenic CO₂ (i.e., carbon in bioethanol); and LUC GHG emissions. Combustion emissions are the most significant GHG emission source for all fuel pathways; however, they noted, in the five bioethanol cases, biogenic CO₂ in ethanol offsets ethanol combustion GHG emissions almost entirely.

Because of the ongoing debate about the values and associated uncertainties of LUC GHG emissions, they produced two separate sets of results for ethanol: one with LUC emissions included, and the other with LUC emissions excluded. To show the importance of key parameters affecting WTW GHG emissions results for a given fuel pathway, they conducted a sensitivity analysis of GHG emissions with GREET for all six pathways with P10 and P90 values as the minimum and maximum value for each parameter. Findings of this exercise included:

• Petroleum gasoline refining efficiency and recovery efficiency of the petroleum feedstock are the most sensitive parameters.

• For corn ethanol, the N₂O conversion rate in cornfields is the most sensitive factor, followed by the ethanol plant energy consumption. Enzyme and yeast used in the corn ethanol production process are not among the five most influential parameters in the corn ethanol life cycle.

• For sugarcane ethanol, the most significant parameters, in order of importance, are ethanol yield per unit of sugarcane, the N₂O conversion rate in sugarcane fields, nitrogen fertilizer usage intensity, sugarcane farming energy use and the mechanical harvest share. Sugarcane farming is evolving as mechanical harvesting becomes more widespread and mill by-products are applied as soil amendments.

• The three cellulosic ethanol pathways have similar results. The electricity credit is the most significant parameter (except for switchgrass ethanol, for which the N₂O conversion rate is the most significant).

• Enzyme use is a more significant factor in cellulosic ethanol pathways than in the corn ethanol pathway because the greater recalcitrance of the feedstock currently requires higher enzyme dosages in the pretreatment stage.

• The impact of fertilizer-related parameters on WTW GHG emissions results depends on the fertilizer intensity of feedstock farming.

Resources

• Michael Wang et al. (2012) Well-to-wheels energy use and greenhouse gas emissions of ethanol from corn, sugarcane and cellulosic biomass for US use. Environ. Res. Lett. 7 045905 doi: 10.1088/1748-9326/7/4/045905

http://www.greencarcongress.com/2013/01/wang-20130122.htm

Easy Energy Systems

URL: 

Easy Energy Systems

Description: 

Specializes in the manufacture and support of Modular Ethanol Production Systems (MEPS).

Their Modular Ethanol Production Systems are:

• Fully Automatic
• Scalable
• Efficient Production
• Increased Safety and Byproduct Feed Value
• Durable Construction
• Price Protection Hedge
• Easily Shipped and Installed
• Environmentally Friendly

Corn Stover as a cellulosic ethanol source

Economist: Take 'stalk' in corn stover as state's ethanol future and Purdue Study Concludes Corn Stover Better Economically Than Switchgrass for Indiana Cellulosic Ethanol

"Cellulosic ethanol made from corn stover and switchgrass could be the next big thing in liquefied energy." At least in corn producing states like Indiana (the study was published by Purdue Univ). Generally ethanol derived from Corn has been seen as a bad idea because it is diverting food to make fuel. There are food riots around the world for a couple years now, due to higher prices for food, and these higher prices may be due (in part) to the diversion of corn (etc) into making fuel.

However Corn Stover is a byproduct of corn production which isn't the food portion of the corn plant. It is the other part, the stalks and leaves. This can be processed as cellulosic ethanol without diverting food for fuel.

Purdue conducted a study comparing Corn Stover with Switchgrass, and this Stover stuff came out better. However it looks to me their figures accounted only for monetary inputs, that by the money inputs to processing Stover it comes out monetarily better than processing Switchgrass. The article doesn't discuss whether it is better from the standpoint of energy inputs.

http://en.wikipedia.org/wiki/Corn_stover

Gives some background on what Corn Stover is.

It says that in Europe (Netherlands and Belgium) Stover is used as animal feed during the winter. They harvest the entire plant and crush the part which isn't the corn husk.

The wikipedia article has this quote: “some agronomists question whether taking stover out of the field annually will have a negative impact on soil fertility and structure.” (link) I expect what they're getting at is if the Stover is left on the field then it will biodegrade on its own and become part of the future soil. But if it is removed then the soil isn't replenished by having the composted plant matter (Stover) feeding into the soil.

GMO Corn-Stover Eats Itself, Makes Ethanol Processing A Breeze and Researchers Modifying Corn With Genes to Produce Enzymes to Enable Simpler Production of Cellulosic Ethanol

"Researchers at Michigan State are trying to get corn-stover to digest itself after harvest. Doing so would mitigate the costly pretreatment steps needed for the production of cellulosic ethanol from the non-edible parts of the corn plant." -- This research would be an optimization of the processing of Stover.

The method is to genetically modify the corn -- so that it produces enzymes required to make the Stover break down more quickly. Uh.. lessee, they're adding a feature to Corn so that the byproduct can be reused more readily? This sounds like a way to distance food from being food, or rather they're putting effort into designing food with featureitis that isn't food-like. This reminds me of a conceptualized nightmare picture I saw long ago of "food engineering" gone awry; the idea was to make tomato's that packed more tomato per unit of space and therefore they genetically modified tomato's so they grew in a cube, because round tomato's have wasted space in the gaps due to round shape.

uh.. wait... Because it is only in the vacuole of the green tissues of plant cells, the enzyme is only produced in the leaves and stalks of the plant, not in the seeds, roots or the pollen. Meaning they've worked out how to genetically modify it so only the leaves and stalks are producing this enzyme. I feel much better.. maybe.

Measuring The Merits Of Corn Stover-Based Ethanol

This covers some of the same ground as before, but it goes into more details on the tradeoff with removing Stover versus leaving it in place. They say Stover left in place "may help prevent soil erosion caused by strong winds or intense rainfall. It also replaces lost nutrients and sequesters carbon in the soil, lessening CO2 accumulation in the atmosphere as a greenhouse gas and its contribution to global climate change." Hmm.. Stover left in place is a carbon sequestriation method? Really? And we want to interfere with this so we can make fuel?

Researchers Developing Machinery To Harvest Corn Stalks And Leaves

This discusses farm machinery being designed which makes it easier to harvest Stover at the same time corn is harvested. In the past it would take two combines to harvest the Stover and Corn, or else the Stover would simply be left in the field. This new machine is a simple addon to existing combines or I suppose could be built as a combined unit which does it all at once to harvest both corn and stover.

Nutrient removal when harvesting corn stover

This is excellent detailed examination of the chemical and nutrient makeup of stover. By removing stover from a field you are removing nutrients and carbon from the field, as discussed above.

It makes it clear that one effect of removing Stover would be the need for increased use of fertilizer. Fertilizer (in the U.S.) generally is made from oil.. soo.... removing Stover to make fuel causes an increase in oil consumption through increased fertilizer use???

Beef: Turn Corn Stover to Low Cost Pasture

A recommendation that Stover can be a good low cost cow feed. Hmm... sounds familiar..

Improving Biodegradability and Biogas Production of Corn Stover through Sodium Hydroxide Solid State Pretreatment

Chinese researchers in Beijing also researching methods to improve processing efficiency of Stover.

Article Reference: 

Economist: Take 'stalk' in corn stover as state's ethanol future

http://www.projectliberty.com/

http://en.wikipedia.org/wiki/Corn_stover

GMO Corn-Stover Eats Itself, Makes Ethanol Processing A Breeze

Researchers Modifying Corn With Genes to Produce Enzymes to Enable Simpler Production of Cellulosic Ethanol

Measuring The Merits Of Corn Stover-Based Ethanol

Purdue Study Concludes Corn Stover Better Economically Than Switchgrass for Indiana Cellulosic Ethanol

Researchers Developing Machinery To Harvest Corn Stalks And Leaves

Nutrient removal when harvesting corn stover

Beef: Turn Corn Stover to Low Cost Pasture

CORN STOVER AS A BIOFUEL

Corn Stover Removal Decreases Soil Carbon, Impacts Crop

Improving Biodegradability and Biogas Production of Corn Stover through Sodium Hydroxide Solid State Pretreatment

http://www.google.com/search?q=+Corn+Stover

extvideo: 

Switchgrass Science - Partners Video Magazine

URL: 

Switchgrass Science - Partners Video Magazine

Fueling America - Episode 20

Description: 

At the University of Tennessee, switchgrass is all the buzz - a plant that's farmer & environment-friendly, and a cheap alternative to high-priced corn for making ethanol. Switchgrass Science is a segment from Partners Video Magazine's latest episode, Fueling America.

extvideo: 

Zeachem

URL: 

Zeachem

Description: 

ZeaChem's innovative process was designed for high yield. The company is pioneering biorefinery technology using combinations of biochemical and thermochemical processing steps. The biochemical processing step converts fermentable sugars in the cellulosic biomass into acetate, which is then recovered from the broth as an ester. The thermochemical processing step converts lignin and other non-fermentable materials in the cellulosic biomass into hydrogen. By combining these two streams in a hydrogenolysis reaction, ZeaChem produces ethanol. Unlike other processes, the Zeachem process uses all fractions of the plant - cellulose, hemicellulose, and lignin, giving it much higher yield.

Cellulosic ethanol: A fuel for the future?

Range Fuels has announced that it has received a permit to build an ethanol production plant in rural Georgia that uses wood chips as its feedstock. It plans to break ground on the plant this summer. The plant will gather wood scraps from the logging industry and process it to make ethanol.

Cellulosic ethanol processes are supposed to be more efficient than making it from corn. It has less intensive farming needs, and can be derived from a wide range of biomass sources.

Their website describes a simple two-step technology of converting biomass (all plant and plant-derived material) into a gas using heat, pressure and steam. The synthetic gas is converted, in the second step, into a liquid ethanol using a catalyst.

In Michigan Macsoma is working on a similar project.

Making ethanol from the cellulose in agricultural and forestry waste rather than corn produces less greenhouse gases, according to environmental groups. An NRDC study found that, on average, corn-based ethanol reduces greenhouse gas pollution by 18 percent for every gallon of gasoline displaced.

Article Reference: 

Cellulosic ethanol: A fuel for the future?

Cellulosic ethanol plant to open next year

Mascoma

URL: 

Mascoma

Description: 

Mascoma envisions a world with broad access to sustainable, renewable, and affordable energy. We will provide a significant portion of this energy through the low-cost, efficient and environmentally beneficial use of cellulosic biomass technologies.

Building on recent transformative research advances in enzymes, organisms and production technologies/ processes, Mascoma is playing a pivotal role in the eventual replacement of gasoline with cleaner, low-cost, renewable ethanol. Mascoma is at the forefront of establishing cellulosic ethanol production facilities with technology derived from both in-house research and partnering.

Range Fuels

URL: 

Range Fuels

Description: 

A privately held company funded by Khosla Ventures, LLC, arguably the top venture firm in the U.S. focusing on alternative, clean (green) energy systems. Our leadership team melds experience from the fast-paced, high-tech world, and the technologically intense coal, coal gasification, and gas-to-liquids industries. They convert biomass into fuel-grade ethanol using emerging clean energy technologies. Biomass includes all plant and plant-derived material, such as wood, switch grass, corn stover, and miscanthus grass – making it a renewable energy resource that produces no net greenhouse gases.

Blue fire ethanol

URL: 

Blue fire ethanol

Description: 

BlueFire Ethanol, Inc. is established to deploy the commercially ready, patented, and proven Arkenol Technology Process for the profitable conversion of cellulosic ("Green Waste") waste materials to ethanol, a viable alternative to gasoline. BlueFire's use of the Arkenol Process Technology positions it as the only cellulose-to-ethanol company worldwide with demonstrated production of ethanol from urban trash (post-sorted MSW), rice and wheat straws, wood waste and other agricultural residues.