People aren't the only consumer of grains. You have biofuels, as well as livestock feed. Biofuels are likely having a bad time with the breakdown in OPEC. With livestock, people might eat a bit less meat, but I donno if that's really gonna move much. But directly to your point, grain alcohol products might drop a smidge with restaurants out of commission for months. Even if people only drink marginally less, they'll be paying way less for it and I imagine some of that margin cut trickles down the supply chain.

More darkly, there may be 1 percent fewer people around to eat bread, steak and drink vodka.

Meat takes a huge hit in economic downturns. Meat is what eats the grains sold in futures markets.