> I very much doubt it would have survived as long as it has as a technology if it were a net energy loss.

Most of the assessments I have seen generally always show that bio-ethanol is a net loss. Only subsidies keep it afloat.

None of the bio-* will make any sense until we have a lot more renewable electricity on the grid. At that point, producing bio-* will basically become an energy storage solution and a way to soak up excess energy production that you couldn't store any other way.

As an aside, I suspect once transport and commuting are handled by EV vehicles, ethanol will stick around as a small scale fuel for motorsport enthusiasts.

Frankly, I love my combustion engines for fun and sport, and while I fully support the switch to EV, I have long been wondering how the switch will effect my ability to use them for fun Sunday drives. Eventually they will be banned from the roads and the production and distribution of petroleum will slow right down.

With many motorsport vehicles using Ethanol based fuels for its lower temperature burn and higher power output, I suspect that is the fuel that will stick around as a special use product. Appropriately priced, no doubt.

economically a net loss or ecologically?

I sort of assume both, but I'd like to hope for one of them.

Both. Here's some data from the late Prof. MacKay: http://www.withouthotair.com/Errata.html#284 :

" 1 acre produces 122 bushels of corn per year, which makes 122 x 2.6 US gallons of ethanol, which at 84000 BTU per gallon would mean a power per unit area of {0.2 W/m^2}; however, the energy inputs required to process the corn into ethanol amount to 83,000 BTU per gallon; so 99% of the energy produced is used up by the processing, and the net power per unit area is about {0.002 W/m^2}. The only way to get significant net power from the corn-to-ethanol process is to ensure that all co-products are exploited; including the energy in the co-products, the net power per unit area is about 0.05 W/m^2."

Ethanol production has never been a net positive for energy production. It has always survived to maximize the use of the subsidies the american corn farmer.

Don't underestimate the power of farming subsidies and lobbying.

Very much so. We should not have any of these laws; if bio-whatever makes economic sense, you won't need laws mandating its use.

It you wanted to kickstart a technology I think it could make sense for shorter periods of time. For example Electric Vehicle tax credits make it much easier for car companies to develop their electric car lines, but the credits expire after so many cars.