In discussing ethanol from corn, we need to consider the factors of supply, demand and cost of production. I think Trump has examined the economy of corn and how the introduction of the ethanol economy makes that product bring the maximum benefit to both the consumer and the producer.
We have seen how the cost of corn production is driven by oil prices, fertilizer, seed etc. which in the past has driven up corn prices. Today the price of corn, if it were primarily used for food, would be lower then the cost of production because there is no market for all of the corn U.S. growers are capable of producing. Because of technology, U.S. corn production has gone from and average of 35-50 bushels per acre to close to 200 average today. With the increased costs of production, the profitability of raising corn quickly reaches a threshold where crop failures can create a disastrous results. To increase demand and raise prices so that corn producers can operate in the safety margin of profitability, U.S. growers have been paid by government not to grow corn.
One needs to understand supply/demand economics to see the value ethanol production has on corn’s price and the profitability to raise it. Corn prices will rise if there are markets for it. If not, corn prices will go down and with it, cause corn production to go down until the market price comes to a point that it is profitable to raise it. In fact, this encourages producers to grow less corn to drive profits as high as possible. When this happens, and if food production is the only use of corn, you will not like what happens. Ethanol production for fuel is like a buffer on the demand side of the equation. When demand is low from the food production side, the production for fuel will increases the demand which increases the price and makes the production profitable. This is the demand side of the equations.
Now on the supply side, when more corn is produced, it should drop the price for the consumer. That is not good for the producer because it reduces the profitability to produce corn. However, with the use of corn for ethanol, corn is made profitable to produce, no matter how much is produced. That is because the price of ethanol is determined by the fuel market, not the food market. It is a win win situation for the producers and the consumer because the overall effect is it keeps the price to the consumer as low as possible while maximizing the profitability to raise it.
If something makes economic sense to do, no one has to mandate it, people do it save money/make a profit. That's how capitalism works.
The rationalization that goes into justifying forcing consumers to buy something they don't want is amazing. It is how crony capitalism works. And who gets what is dependent on who has the best lobbyist and is why DC is a cesspool...