Energy gain in biofuel production

[danie]

What is the net energy gain in biofuel production from corn.

If there is a gain of 50 %. and an internal combustion engine uses only 40 % of the availeble energy it dont make much sense to take this route. Can anybody comment on it.

[SH3RL0CK]

The net energy gain depends on who you ask. Most credible sources seem to indicate an EROEI of about 1.8; meaning that for every 1 unit of energy expended, 1.8 units are recovered. But also keep in mind that the EROEI isn't necessarily the best measure of the usefulness of corn as a biofuel.

 

For example, after the ethanol is obtained, the "distillers grain" or remnants can still be fed to livestock as is 91% dietary equivalent of straight corn. In other words, we would have grown the corn anyway to feed our cattle.

 

Another point to consider is that if we have abundant and cheap solar, wind or other energy sources (just not in a liquid fuel form and because of our infrastructure it is necessary to supply liquid fuels to run our cars), then even a dreadful EROEI might not be bad. Consider a hypothetical example where electricity is so plentiful it is free. Then the EI part costs nothing...and the cost of the ethanol fuel might be extremely cheap even with very poor EROEI...so much so that it might replace other sources of liquid fuel with a much better EROEI (it is the price at the pump that matters to the consumer).

 

I'd suggest you do a search for this as there have been many useful threads on this topic within these forums.

[CaptainPanic]

The question is very hard to answer, because:

 

1. There exist many types of biofuel from corn: bioethanol, bio-gas (methane), bio-oil (pyrolysis oil)... so you should specify this first

2. The methods used to grow the plants (especially fertilzers), harvest the plants, and convert them into fuels really affect the efficiency a lot.

3. Climate is a big influence as well.

4. There is more than 1 type of corn, and the choice of the type of corn influences points 2 and 3.

 

Therefore, the numbers vary a lot... and entire faculties and research institutes are dedicated to answer this question.