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Is Biofuels Really Contributing To Greenhouse?


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#1

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Posted 10 February 2008 - 08:18 AM

I find it misleading since whatever the case is, biofuels will eventually pay back the carbon debt as opposed to using conventional fuels where you can repay the debt at all..

#2 alljacks

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Posted 17 September 2008 - 10:07 AM

QUOTE (petrochemical-strategist @ Feb 10 2008, 08:18 AM) <{POST_SNAPBACK}>
I find it misleading since whatever the case is, biofuels will eventually pay back the carbon debt as opposed to using conventional fuels where you can repay the debt at all..


The Renewable Fuels Association has some interesting reading on this. There are many bio refineries under construction in the USA and also already in place. The contribution to the fuel requirements is significant. Now all we have to do is learn how better to use the fuel we have.

#3 djack77494

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Posted 17 September 2008 - 05:06 PM

I'm not sure I understand the question, but my take on conventional fuels vs. biofuels is:
1) Fossil fuels include the extraction of hydrocarbons that would otherwise remain buried in the earth for geological times. When burned, the contained carbon is released into the atmosphere for a negative greenhouse gas impact (or more CO2 in the atmosphere).
2) Biofuels are not buried in the earth. They are produced, perhaps in a round-about manner, by extracting (removing) CO2 from the atmosphere and immobilizing it in the biofuel. That same carbon may be soon re-emited to the atmosphere when the biofuel is burned, but it had recently been CO2, so the greenhouse impact in neutral.

#4 contextion

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Posted 19 February 2009 - 07:00 AM

The difference between biofuel and fossil fuel is the Carbon 14/13 ratio. The biofuel has new C from cellulose and the fossil fuels have old C from the ground. If the biofuel is from tires there will be C14 from natural rubber and C13 from the synthetic rubber.

#5 gvdlans

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Posted 19 February 2009 - 07:49 AM

If it takes one liter of conventional fuel to produce one liter of biofuel the nett result is zero.

It it takes more than one liter of conventional fuel to produce one liter of biofuel the nett result is negative.

Conventional fuel may be used to produce fertilizers, to harvest the crops, to transport the corn (or other plant material), to convert the corn into ethanol, to transport the ethanol to the user, etc.

QUOTE
Biofuels as currently rendered in the U.S. are doing great things for some farmers and for agricultural giants like Archer Daniels Midland and Cargill, but little for the environment. Corn requires large doses of herbicide and nitrogen fertilizer and can cause more soil erosion than any other crop. And producing corn ethanol consumes just about as much fossil fuel as the ethanol itself replaces. Biodiesel from soybeans fares only slightly better.


From: National Geographics Magazine October 2007 article

#6 mrj

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Posted 20 February 2009 - 06:40 AM

Dear gvdlans,

The need of conventional fuel depends upon feedstock used for ethanol production.
If you consider the production of ethanol from sugary feedstocks (Sugarcane), then the practical conventional fuel requirement is Zero.

mrj

#7 gvdlans

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Posted 20 February 2009 - 12:02 PM

QUOTE (mrj @ Feb 20 2009, 12:40 PM) <{POST_SNAPBACK}>
Dear gvdlans,

The need of conventional fuel depends upon feedstock used for ethanol production.
If you consider the production of ethanol from sugary feedstocks (Sugarcane), then the practical conventional fuel requirement is Zero.

mrj

From the same article in National Geographic Magazine:

QUOTE
While corn ethanol's energy ratio hovers around breakeven, "we get eight units of ethanol for every one unit of fossil fuel," says Isaias Macedo, one of Brazil's leading sugarcane researchers. Experts estimate that producing and burning cane ethanol generates anywhere from 55 to 90 percent less carbon dioxide than gasoline. And Macedo envisions even greater efficiencies. "We can do the same thing with two-thirds or half of the bagasse, better manage tractors in the field, and approach levels of 12 or 13."

Even sugarcane isn't without its problems. While nearly all of São Martinho's cane is machine harvested, most Brazilian cane is cut by hand; the work, though well paid, is hot, dirty, and backbreaking. Cutters die of exhaustion every year, say leaders of their union. And to kill snakes and make the cane easier to cut by hand, the fields are usually burned before harvest, filling the air with soot while releasing methane and nitrous oxide, two potent greenhouse gases.

The expansion of Brazil's cane acreage—set to nearly double over the next decade—may also be contributing to deforestation. By displacing ranching in existing agricultural areas, sugar may be adding to the pressures that send cattlemen deeper into frontier territory like the Amazon and the biologically diverse savannas known as the cerrado. "If alcohol is now considered a 'clean' fuel, the process of making it is very dirty," says Marcelo Pedroso Goulart, a prosecutor for the Public Ministry of São Paulo. "Especially the burning of cane and the exploitation of the cane workers."


#8 Art Montemayor

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Posted 20 February 2009 - 01:20 PM


Mrj:

Where is the information and data found that a sugar refinery is auto-sufficient in energy? In other words, where is a sugar refinery to be found that is 100% relient on its own production of energy?

Even the National Geogaphics article which, Guido quotes, does not go into the realities and hard facts that growing sugar cane requires fertilizer - especially in tropical regions such as Brazil, where the soil is sparse of natural minerals and is continuously leached out by rainfall. The required fertilizer has to come from other means - and those means at present are based on fossil fuels.

Additonally, sugar cane cannot be harvested, gathered, and transported without motorized and mechanical means - all requiring fuels. The larger the sugar estate, the more the fuel demand. All agricultural feedstock industries - such as sugar cane - are based on the economics of having cheap fuel and cheap labor. Without either, the industry cannot economically compete. Of course, if we institute Socialism and its subsidies and financing of such industries then we can easily hide or camoflauge the end results and call it an "economic" success. But the hard facts are that when forced to compete in an open, free market place, the subsidized industry can only fail. Pure, engineering economics up to now have demonstrated that there is less energy coming out of the Sugar Estate than what is going in. That's to be expected and is no great surprise. What would be a surprise is what you are stating: The sugar estate produces a NET energy surplus. If so, where is the factual data that proves this. I've seen the empirical model out in the field in my years in the Caribbean, and it needs external energy to exist.

I wish I could rely on making ethanol out of sugar cane without any external energy except the sunlight and human labor to fuel the entire process. I don't believe that is physically possible.






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