Fueling ethanol production

Grain-based ethanol production is expanding rapidly and is the primary factor leading to major increases in the amount of corn grown in the USA and elsewhere. Increased corn acreage and fertilizer application rates due to corn prices will increase N and P losses to streams, rivers, lakes, and coastal waters, particularly the Northern Gulf of Mexico and Atlantic coastal waters downstream of expanding production areas. Harvest of corn stover for cellulosic ethanol production would likely increase erosion (sedimentation) and nutrient loads, which will adversely affect these already nutrient-stressed waters. It is critical that a broad suite of conservation measures, particularly nutrient management, are rigorously implemented on new or more intensively managed corn lands, particularly under continuous corn production to partially offset an increased potential for nutrient loss; for example, the use of precision and variable-rate applications of fertilizers and the Late Spring Nitrate Test. Additional measures include interseeding corn with cover crops and the inclusion of buffers or riparian filter strips to minimize edge-of-field runoff of N and P.

Dried distiller’s grain from fermentation is rapidly becoming available for use in animal rations, particularly for beef and dairy cattle. Due to the high P content of DDGs, the P content of manures will increase, which will further enhance the mobility in runoff of P applied in these manures. The use of DDGs in animal rations should not be done at such a level as to increase N and P contents of feeds above nutritional requirements. Otherwise, N and P contents of manure will be greater than using current feed management practices, enhancing the potential for nutrient enrichment of runoff. The likely concentration of animal facilities near ethanol production plants must be accompanied by sound nutrient management planning and other conservation measures to avoid the soil and water-quality consequences of N and P accumulation in areas used to land apply manures.

The development of efficient and competitive fermentation technologies and supporting infrastructure to allow development of a perennial grass or waste-based cellulosic ethanol industry could provide a long-term sustainable approach to ethanol production. A cellulosic renewable energy approach could provide multiple ecosystem services including energy, C sequestration, improved water quality and fisheries habitat, and improved soil quality and productivity. As markets develop for each of these services/products, perennial grass production for ethanol generation may become economically competitive with, or even superior to, grain or crop residue fuel-stocks for ethanol production. Any alternative fuel production technology may have impacts on water quality. As a result, it is important to make policy and programmatic and scientific decisions that avoid or mitigate the unintended environmental consequences of biofuel production during development of the industry to avoid the much higher costs of remediation and ecosystem restoration at a later date.