Agronomic Evaluation of Ashes Produced from Combusting Beef Cattle Manure for an Energy Source at an Ethanol Production Facility

Abstract

A large international energy company is planning to use beef cattle manure from concentrated animal feeding operations (CAFOs) to supply part of the energy required to operate a 435 million L/ year ethanol facility at Hereford, Texas. If this proves successful, similar facilities may follow. A major concern, however, is the large amount of ash that will result from burning the feedlot manure. The manure will be burned in a fluidized bed combustion system, similar to those used for coal and lignite, and will produce 28 Mg of ash for every 100 Mg of manure (dry basis). In order to assess the viability of land application of this ash, the impacts of manure ash application to soil characteristics and plant growth were determined. Results from the soil incubation, sulfuric acid, and greenhouse studies indicate that while some of the ash phosphorus (P) is plant available, the P content of the ash is so low that extremely large amounts would have to be added to soil to supply meaningful amounts of P.