This spring farmers responded to the ethanol industry's demand for grain by increasing their corn acreage by 19 percent over last year, according to U.S. Department of Agriculture estimates. If they begin growing biomass crops such as switchgrass for the production of ethanol from plant fiber what would be the effects on the land and water, Anex asks.
Anex, an Iowa State associate professor of agricultural and biosystems engineering and associate director of Iowa State's Office of Biorenewables Programs, is examining the sustainability of a shift to an American agriculture that produces biomass for fuel as well as food and fiber.
'It may well be that the development of biomass-based crops production systems can have as profound an impact on agriculture and its environmental footprint as it does on energy security and the global climate,' Anex and co-authors wrote in a new paper published online by 'Crop Science,' the official publication of the Crop Science Society of America.
'Whether this is a positive impact or a negative impact will depend largely on how biomass feedstocks are produced and converted, and the extent to which these two activities are integrated, wrote the team from Darthmouth College and Iowa State's Agronomy Department.
Their paper, 'Potential for Enhanced Nutrient Cycling through Coupling of Agricultural and Bioenergy Systems,' reports that as much as 78 percent of the nitrogen fertilizer needed for crops could be recovered from an integrated biological and thermochemical process that converts switchgrass to ethanol.
The study says such nutrient recovery and recycling could improve the sustainability of biomass production and the amount of energy required to produce ethanol from plant fiber.
Plant fiber would be converted to liquid fuels by pre-treatments and fermentation, the researchers say. The co-products of fermentation would be dried and heated to turn the solids into gases.
The gasification would leave plant nutrients in the resulting ash and ammonia. The nutrients in both streams could be recovered and returned to the fields that produced the biomass.
And that potential for nutrient recycling means there is potential for a new kind of agriculture feeding a sustainable bioeconomy.
'By creating a large, new domestic demand for agricultural products, the advent of commercial-scale conversion of biomass into ethanol and other industrial chemicals is likely to have a strong influence on the design of agricultural systems,' the researchers wrote. 'The possibility of recycling nutrients from the biorefinery to the agricultural system that produces the feedstock may allow substantial improvements in both sustainability and production efficiency.'
Sustaining biomass production depends on many variables such as soil type and slope, soil organic matter and the amount of biomass harvested.
To help farmers begin to understand how collecting biomass from their fields may affect soil fertility, erosion, energy needs, labor and the bottom line, Anex and a team of Iowa State researchers have added bioeconomy elements to I-FARM, a web tool that helps farmers simulate and plan various changes to their operations.
I-FARM is free and can be found at http://i-farmtools.org. Its focus is on the upper Midwest but weather and soils data from 28 states are accessible from its database.
Anex's study of the sustainability of the bioeconomy is being supported, in part, by grants from the U.S. Department of Agriculture, the U.S. Department of Energy and the National Science Foundation.