In the last twenty years a large number of ethanol firms have established operations in the US. Ethanol, produced from corn, is blended with pure gasoline to produce fuel. Producers hold an option to turn off unprofitable plants. Blenders choose to substitute ethanol for gasoline at or beyond the mandate set by the government. We propose an equilibrium model for blenders and producers that accounts for government measures and for real optionality embedded in the industry. The model, driven by corn and gasoline prices, leads to analytical expressions for the price and output of ethanol, and to policy implications on the impacts of the mandate and blend credit. The model also leads to closed form valuation for an ethanol producer. Using data between 2000 and 2017 we confirm that, as in the model, ethanol was largely priced as the maximum of rescaled gasoline and corn prices. Historical output levels between the mandate and installed capacity were explained by our theory. Finally, the share price dynamics for the largest public ethanol producer in the US was consistent in some aspects with the value of a real option.