The value of ethanol has also sagged. Its price is created in part by the price of the gasoline it displaces, and gasoline prices have been relatively modest for the past few months.

Mr. Sneller and others in the industry remain optimistic that technological innovations and sound public policy will keep the industry afloat.

Indeed, people here in Macon, in northeastern Missouri, are not as grim about the future of their plant, which is operated and partly owned by POET, an ethanol producer with more than two dozen plants nationwide. The plant has vowed to reopen, and it has retained all 44 of its employees to do maintenance work as it undergoes more than $13 million worth of renovations that it hopes will make it more efficient and able to produce ethanol more cost-effectively.

Signs of transition are evident at the plant. The growling factory motors, pumps and boilers are silent. But a sweet, acidic smell lingers, and signs of construction are everywhere: skid loaders sitting on fresh dirt, wooden planks cut for frames and dusty corners sectioned off with orange cones.

The plant, which President Obama visited three years ago, is adding equipment to allow it to produce corn oil that will provide additional income. It is also instituting technology that can produce ethanol without having to use heat, a move that will save on energy costs.

With the new technology, operators hope they will produce an extra three-tenths of a gallon of ethanol per bushel of corn.

Residents also understand why the plant halted operations.

The drought was particularly brutal here last year, leaving farmers with little to no corn. Don Mutter, who farms in nearby Cairo, said he produced about 25,000 bushels of corn last year, just 5.5 percent of his usual yield. Without corn nearby to purchase, the plant had to spend extra to haul it in from elsewhere. For several months it was operating at a loss. It ceased operations at the end of January.