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Posts Tagged ‘Corn’

Ethanol: More = Less

March 2nd, 2011

A new paper in the American Chemical Society’s Journal – Environmental Science and Technology indicates that over fertilizing corn would affect the cellulosic ethanol production. The team lead by postdoctoral researcher Morgan Gallagher discovered that corn grain and corn’s stalks and leaves respond differently when treated with nitrogen fertilizers. Though the presence of excess nitrogen increases the yield of corn grains, it results in twice the amount of lignin, as nitrogen plays a vital role in the biochemical pathway that produces lignin. And since, the lignin is doubled, the whole process of extracting ethanol from corn stovers becomes complex.

Lignin slowly breaks down with the help of bacteria and hence the process becomes more expensive to remove it by mechanical or chemical processes.

The study, conducted at and in collaboration with the National Science Foundation’s W.K. Kellogg Biological Station at Michigan State University (MSU), showed that although feeding the plant more fertilizer increases the grain’s cellulose content, grain yield quickly hits a plateau. At the same time, the researchers found only a modest increase in plant and stem cellulose.

More here

“Morgan E. Gallagher, William C. Hockaday, Caroline A. Masiello, Sieglinde Snapp, Claire P. McSwiney, Jeffrey A. Baldock (2011) Biochemical Suitability of Crop Residues for Cellulosic Ethanol: Disincentives to Nitrogen Fertilization in Corn Agriculture. Environmental Science & Technology 45 (5), 2013-2020 doi: /10.1021/es103252″

Cellulosic Ethanol Vs Corn

September 24th, 2009

Ethanol production is different when cellulosic biomass is used as the raw material. For ethanol production, fossil energy inputs into the production cycle represent about 2/3 of the energy content of the ethanol produced, and greenhouse gas emissions on a per mile basis are about 2/3 of a gasoline base case, representing an approximately 33% reduction. Ethanol from Cellulosic biomass shows a better energy balance and is sustainable as well.

The reasons why I think cellulosic ethanol can be used against corn

1. Corn is easier, and currently less expensive, to process into ethanol than is cellulosic biomass. However, cellulosic biomass is less expensive to produce than corn by a factor of roughly 2 on a per ton basis, and the amount of ethanol that can be produced per acre of land.

2. For ethanol produced from cellulosic biomass, the energy balance and greenhouse gas emissions are more favorable when compared to corn

3. Relative to corn, production of a perennial cellulosic biomass crop such as switch grass requires lower inputs of energy, fertilizer, pesticide, and herbicide, and is accompanied by less erosion and improved soil fertility.

4. Finally, cellulosic biomass differs from corn kernels in that it contains substantial amounts of non-fermentable, energy-rich components that can be used to provide energy for the conversion process as well as to produce electricity.

Switch-grass vs Corn

July 16th, 2009

Pimentel and Tad W. Patzek, professor of civil and environmental engineering at Berkeley, conducted a detailed analysis of the energy input-yield ratios of producing ethanol from corn, switch grass and wood biomass as well as for producing biodiesel from soybean and sunflower plants. Their report is published in Natural Resources Research (Vol. 14:1, 65-76).

In terms of energy output compared with energy input for ethanol production, the study found that:
# corn requires 29 percent more fossil energy than the fuel produced;
# switch grass requires 45 percent more fossil energy than the fuel produced; and
# wood biomass requires 57 percent more fossil energy than the fuel produced.

In terms of energy output compared with the energy input for biodiesel production, the study found that:
# soybean plants requires 27 percent more fossil energy than the fuel produced, and
# sunflower plants requires 118 percent more fossil energy than the fuel produced.

see more

Cultivation of Perennial grasses better than Corn

July 16th, 2009

Land currently used to grow row crops would provide one source of land for perennial grass production. The primary concern associated with this conversion is that less cropland would be available for food production, leading to diminished food supplies and increased food prices (Carey 2005).

However, this competition could be mitigated if switchgrass is grown on land currently used to grow corn for ethanol. It is estimated that about 20% of harvested corn goes into ethanol production (Yates, 2008).

Based on this percentage and the amount of corn acreage grown in 2008, approximately 16.5 million acres would open up for switch grass production if corn ethanol were replaced.

Miscanthus is Better than Corn

July 15th, 2009

This article caught my eye when I was looking for the ethanol yield of Miscanthus. Sounds interesting !!

In Khosla’s simple arithmetic, with irrigation and other inputs, it would be possible to grow 20 tonnes of crops per acre and each ton of crop would yield 100 gallons of ethanol
Thus 50 million acres would generate as much as 100 billion gallons. He recommended switching over to a tall grass called miscanthus in the US, which would yield a higher profit.

However, this – when also related to land use is where Khosla’s vision may not apply to developing countries, while it may make good sense in the US and Europe.

The fact is that any conversion of land to produce ethanol, particularly if it is with crops like miscanthus that require fertile soil, could only be at the cost of food and fuelwood.

Full article

Low Temperature Gasification of Corn Stover – UMM Encounters Problems

July 9th, 2009

It was interesting for me to read about a unique gasifier that UMM (University of Minnesota, Morris) was experimenting with.

UMM’s goal was to create the first gasifier that incinerates the fuel temperatures of 1,000 degrees or lower, producing gas that can be used to create steam for UMM’s system while also preserving minerals in the ash so it can be used in soils. Now, most solid fuel gasifiers burn heavy density wood at a temperature of about 3,000 degrees, and the ash produced can only be used for limited purposes, such as wallboard.

I think the lower temperature gasification is interesting from many aspects. I am wondering if this is the same as pyrolysis (from all accounts it seems so), or whether this low-temp gasification has features that differentiate it from pyrolysis.

Either way, the following was the unique problem faced by the team at UMM:

But when the system was first fired up, operators learned that gasifying loose stover (which was used as the feedstock) posed substantial problems. The stover is moved into the burner, where air is blown through from the bottom of the burner for combustion. But the loose stover has a density of three pounds per cubic foot and the air moved it around in the burner and created a hole in which all the air would move through instead of maintaining a steady flow.

So, the folks decided that corn stover, the way it was used, would not be appropriate. They turned to a company to compact the stover into a form similar to compressed sawdust fireplace logs. The new stover “logs” have a much higher density of 50 pounds per cubic foot (compared to the 3 lb per cubic foot of loose stover). The density is expected to help the fuel remain in place in the burner and even out the heat and air distribution in the gasification process.

Of course, it costs to compact the stover. How the whole compacting process will affect the economics is not known presently. But this presents an interesting case study in waste biomass gasification

Source credit: Morris Sun Tribune

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