Carcano said:
Ethanol is very rarely used to make biodiesel for two reasons:
1. It is a much larger molecule than methanol and requires longer reaction times and higher temperatures during processing.
2. Ethanol is also more difficult to recycle due to its azeotrope with water in a 95% concentration.
So, why is all this processing with toxic chemicals like methanol and sodium hydroxide (caustic soda) neccessary - because diesel engines don't run well on pure vegetable oil unless the fuel tank is heated, otherwise the oil is too thick and viscous to flow and ignite well in the engine.
I have heard of people using mineral spirits, as well as one or two other nasty chemicals, to thin it down - apparently this was a technique used in Europe during WWII, when diesel fuel was rationed.
First point. Ethanol biodiesel can be home-brewed at room temperatures. Home brewing with ethanol is more tricky than with methanol. Potassium hydroxide can be used instead of lye so processing times are about equal, about 6-8 hours. How long does it take to ferment grain to make ethanol?
Commercial processing of ethanol biodiesel should be a relatively simple operation, if it can be done at home.
Yes, methanol is classified as a toxic chemical. It is wood alcohol. You do realize that all ethanol used in 'gasahol' blends comes from processed gasoline, not grain alcahol don't you? It is cheaper to get the 199 proof ethanol from petroleum than it is with grain.
I already mentioned why esters of oil was preferred over pure vegetable oil. And yes, diesel engines do run fine on pure vegetable oil without 'heating the fuel tank' EXCEPT in cold temperatures, like near freezing. Again, engine deposits over time and gelling at cold temperatures are the main drawbacks of pure oil.
Here is a chart that might interest you:
"The concept of "input efficiencies for fossil energy sources" was introduced as a component of the study. This was meant to account for the fossil energy used to extract, transport and manufacture the raw material (crude oil) into the final energy product (gasoline). According to the study, gasoline has an energy ratio of 0.805. In other words, for every unit of energy dedicated to the production of gasoline there is a 19.5 percent energy loss.
In summary, the finished liquid fuel energy yield for fossil fuel dedicated to the production of ethanol is 1.34 but only 0.74 for gasoline. In other words the energy yield of ethanol is (1.34/0.74) or 81 percent greater than the comparable yield for gasoline.
Bio-Diesel versus Petroleum Diesel
A similar study was co-sponsored by the United States Department of Energy and the USDA, entitled, "Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus."
The study, published in May 1998, states; "Biodiesel yields 3.2 units of fuel product energy for every unit of fossil energy consumed in its life cycle." The report continues, "By contrast, Petroleum diesel's life cycle yields only 0.83 units of fuel energy per unit of fossil energy consumed." According to this analysis, the energy yield of biodiesel is (3.2/0.83) 280 percent greater than petroleum diesel fuel.
Summary - Energy Balance/Energy Life Cycle Inventory
Fuel * Energy yield Net Energy (loss) or gain
Gasoline 0.805 (19.5 percent)
Diesel 0.843 (15.7 percent)
Ethanol 1.34 34 percent
Biodiesel 3.20 220 percent
* Life cycle yield in liquid fuel Btus for each Btu of fossil fuel energy consumed.
The positive energy ratio displayed by ethanol and biodiesel is accounted for by the contribution of solar energy collected by the crop from which the fuel is made. This energy is considered "renewable" because a new crop is raised each year.
http://www.mda.state.mn.us/ethanol/balance.html