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Comment by Spooky23 | Hacker News Reader

Mandating its existence has other strategic advantages as well -- oil price shocks can and will happen in the future, so having the infrastructure to manufacture biodiesel and ethanol in place has a benefit as well.

There's a short, medium and long term outlook here. In the short term, there's a wastage of $5.4B. In the long term, burning things for fuel is bad. In the medium term, being able to moderate swings or ensure minimum supply of fuel mitigates risk that endanger the economy as a whole.

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But this doesn't actually work yet. Oil prices are transmitted through to biofuels because the biofuel supply chain depends critically on fossil fuel inputs. For example, planting, harvesting, and transport of corn and soy feedstock is currently completely reliant on fossil-fueled machinery. This may change in the future, but the current reality is no better than a 1-to-1 transformation of fossil fuel into biofuel.

This is true of corn but I'm not so sure on soybeans. Do you have a source on the total conversion rate for soy?

According to the source below, the partial conversion rate is about 57 gallons per acre (at 39 bushels/acre). It takes WAY less than 57 gallons of biodiesel to farm one acre of soy. Modern practices are really only going to have 3-4 passes (no till plant, early spray, maybe a later spray and harvest). After that is is mostly bulk trucking which shouldn't be much per acre.

Remember that unlike corn, soy requires very little/no fertilizer due to it being able to fix its own nitrogen. It is mostly the fertilizer the kills corn.

Source: https://www.uaex.edu/publications/PDF/FSA-1050.pdf

Googling for the EROI and NEB of soy biofuel, numbers appear to be significantly better than for corn, but still no better than low single digits. Also, soy uses a lot more water than corn, which imposes another host of considerations, including higher transportation cost due to regional growing restrictions.

Cane ethanol seems to do better than soy fuel. I'm also aware that new biofuel "generations" have the potentional for much higher returns, but these things are either still emerging technologies (e.g., cellulosic and algae) or horrifically damaging to the environment (e.g., palm oil biofuel).

>This may change in the future, but the current reality is no better than a 1-to-1 transformation of fossil fuel into biofuel.

I was with you until this. a brief thought experiement makes it seem impossible that it would be 1 to 1, but rather that some smaller amount of fossil fuel used would yield a much larger amount of biofuel

This topic is way too complex to be experimented upon by mere thought. For example, take a gander at this discussion on corn ethanol EROEI a few years back. Lots of data, detailed analysis, vigorous debate, and a headline conclusion of an EROEI of 1.07.

There's a lot of debate about this, with numbers varying due largely to differing assessments of inputs and credits for byproducts, but I have never seen a convincing EROEI for corn ethanol over about 2.

EDIT: I forgot to include the link! Here it is: http://netenergy.theoildrum.com/node/6760

How so? If the market is manipulated via farm subsidies or biofuel subsidies it's entirely possible groups might not be overly worried about the efficiency of the process and expend the same amount of fossil fuel (or more) to obtain an equal amount of biofuel.

Remember, biofuel costs significantly more. Pump prices include taxes, so difference in pre-tax vs pre-subsidies of 1.80 $ is huge.

The value of biofuels is simply cushion in case of poor harvests.

Also in the medium term, artificially increasing the price of fuel incentivizes research and development of alternatives.

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