Pay the farmers to put up solar panels instead. You get a lot more energy that way. For example, replace all land used for "energy crops" in Germany with solar panels and you get about as much energy as Germany consumes in total.

I like this, do you have any idea how I can compare revenue per acre?

It must be reasonably close, since both solar fields and traditional crops exist in Germany.

Of course both get subsidised to various extents, and the prices of energy, crops and labour all fluctuate - but you can guess they're equal within a factor of two.

It's not a good environmental policy on balance. It results in only about a 30% reduction in CO2 emissions. It does substantially reduce air pollution compared to gasoline. But we have to devote large amounts of land usage to it, destroying natural habitats, and we pollute water with runoff.

On balance, I would rather emit the CO2, until we can convert transportation fleets to electricity.

The number of people employed in corn farming is insignificantly small. The number of those benefiting from ethanol is even smaller.

It's basically a subsidy to a couple of large agribusiness companies. Nothing to do directly with people-first politics.

On board of what? Farmers were never in the energy business, why do they need to get into it now.

They are big consumers of energy, whether it be natural gas for heating or drying or diesel for machinery, so a carbon tax would hit them hard. They would be vocal opponents of such a thing.

By this logic everybody will be a vocal opponent of carbon tax. It's universal after all and hits everyone equally. But that's the whole point of a carbon tax - to move away from carbon.

As long as the price farmers get goes up to cover their increased expenses, farmers should be fine with a carbon tax. Not sure consumers would be happy with food prices going up. That's why carbon taxes should be accompanied by an appropriate rebate.

If the price of domestic food goes up countries will just start importing more food from countries without a carbon tax. That would really annoy farmers. So any carbon tax needs to be accompanied by carbon tariffs.

It hits everyone equally by use of carbon. It doesn't hit everyone equally overall. $100 a year is an annoyance, especially if rebated. $10,000 a year substantially changes farming economics.

Farmers have ALWAYS been in the energy business. While you do need some nutrients to build the body, the vast majority of the food you eat is used for energy.

Ethanol has no long-term future because the vehicle fleet is already shifting to using no fuel at all.

John Deere already manufactures electric tractors and farmers can simply utilise replaceable battery packs, charged on-site using solar power.

John Deere has made prototype electric tractors. The battery operated one was a ~100 (150?) horse power tractor packed full of batteries that was able to do everything the equivalent diesel tractor could do - for about 1 hour then the battery was dead. Note that the above tractor is considered mid size, the big tractors that sell the best have far more horse power. The other is a tractor with a 1km (or longer?) cable to it can plug into the grid at all times. Neither is practical for real farmers, though they do work.

I'm a Deere Employee. I cannot talk about projects other than the above, but I wouldn't hope for practical electric tractors in the near future.

Counterpoint,

For land travel all electric vehicles make a TON of sense. However, for airline and oceanic travel, the energy density of a battery simply isn't high enough.

Biofuels may be the only carbon neutral way to accommodate such forms of transport.

Counter-counterpoint: Photosynthesis is only 2-4% efficient (measuring solar input to biomatter). Solar panels are ~20% efficient. Making fuel directly from electricity and CO2 is probably (I didn't do the math) more efficient per acre than making fuel from plants. You can of course supplement this with Ethanol made from waste that you get as a byproduct of food production.

It's not an energy efficiency problem, it's an energy density problem.

Burning hydrocarbons peeks out at something like 40% efficiency. Yet we are only now getting to the point where EVs have the same range as ICE vehicles, even though the battery->motor conversion is something like 90% efficient.

Why is that? Because the amount of energy that can be stored in batteries is MUCH lower than the amount of energy released from burning fuel.

Transport needs to carry all of it's energy with it (or, have something like a 3rd rail to provide energy).

That's the argument for biofuels in the future. Not that you can't replace 99% of transport with electricity, but rather some forms of transport require a lot of energy.

We are JUST getting to the point where batteries have enough density to power a prop plane for ~ 1hour worth of flight.

We are no where near the energy density where a cargo ship could sail from china to the US or for international flights.

One alternative to biofuels is hydrogen from something like electrolysis.

One thing I think we'll both agree on. Ethanol for cars/trucks is a terrible idea. EVs are the future there.

The parent post meant making hydrocarbon fuels from electricity, water, and carbon dioxide. You make electrolytic hydrogen from electricity and water and then use it to hydrogenate CO2 to methane. Liquid methane has excellent energy density and would be suitable for fueling rockets, aircraft, and large ocean going ships. Or you could create synthetic kerosene by a different choice of chemical processes, if it's acceptable to trade lower efficiency for a fuel that is conveniently liquid at room temperature and compatible with legacy systems.

https://www.power-eng.com/2020/07/08/power-to-gas-examining-...

https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...

The advantage of synthetic fuels over biofuels is that you can get a lot more fuel out of 100 hectares of solar panels than 100 hectares of crops, because plants are very inefficient at capturing solar energy as useful chemical energy. The advantage of biofuels over synthetic fuels would be lower capital costs. Biofuels have an advantage while non-fossil fuel demand is low, but they can't scale as well.

Since artificially capturing CO2 from the air is expensive and inefficient so far, an attractive hybrid path combines biomass and electrolytic hydrogen to make methane or heavier hydrocarbons. The main role of the plants is to concentrate carbon from the air. A kilogram of dry cellulose has an enthalpy of combustion of 17.5 MJ [1]. It contains enough carbon to make 0.76 kg (47.6 moles) of methane, once fully hydrogenated. That methane has an enthalpy of combustion of 41.9 MJ [2]. The biomass would supply all of the carbon and a minority of the chemical energy while electrolysis would supply the majority of the hydrogen and the final energy content of the methane.

[1] https://en.wikipedia.org/wiki/Cellulose

[2] https://en.wikipedia.org/wiki/Methane_(data_page)

Batteries may not be energy dense enoguh, but hydrogen should be.

As far as I'm aware, nearly all tractors much larger than a lawn mower now use diesel, not gasoline/ethanol. This wasn't always the case, but I understand it to be true particularly since the later half of the 20th century. So for the most part biodiesel, not ethanol, is the relevant biofuel for powering large farm equipment. Their larger trucks burn diesel too, though their pickup trucks and other small road vehicles are often gas/ethanol burners.