Corn Plus — a 40-million-gallon corn ethanol plant that runs on biomass power — sells out of its renewable ash fertilizer a year or more in advance.

“The product is really popular,” says plant manager Matt Rynearson. “There’s definitely a market for the ash.”

The Winnebago, Minn., ethanol maker generates most of its energy needs by burning corn solubles, an ethanol byproduct that is usually sold as livestock feed. Corn Plus sends 80,000 gallons a day of syrup, as it’s called, to its fluidized bed reactor, as fuel. The fine, flour-like ashes left after combustion are pelletized for easier handling and sold as fertilizer.

Corn Plus produces about 7,000 tons of ash fertilizer granules a year. The ashes contain phosphorus, potassium and sulfur, but not nitrogen, which is consumed during fermentation. AURI-sponsored research trials at the University of Minnesota found that Corn Plus’s 0-14-15-4 ash performed as well as commercial fertilizer at both low and high application rates.

A group of local farmers contract for all the plant’s ash, Rynearson says. The growers apply it to their own cropland and sell the excess to other farmers. The granulated product is applied with conventional spinner spreaders.

Corn Plus receives a percentage of ash fertilizer sales, Rynearson says, but the company is not really out to make a big profit from the ash. “The environmental benefits are more important to us. We’re trying to be green.”