Bioeconomy Institute

That Iowa has some of the richest soil in the world is no secret, and a group of researchers at Iowa State University would like to ensure that Iowa’s soil retains its high quality. These researchers are investigating alternative cropping systems and practices such as applying biochar (also called agrichar) to the soil to protect it from the loss of organic matter and fertility that could accompany the proliferation of biorefineries across Iowa’s landscape. The Iowa State research team is looking at the impact of the removal of large amounts of crop residue from agricultural fields. Their goal is to ensure that farmers will be able to generate the large amounts of biomass feedstocks that cellulosic biorefineries will need to meet the
demands of a developing bioeconomy, while also being able to return carbon
and important nutrients such as phosphorus, potassium and nitrogen back to the soil.

“Unlike livestock and people, who need these nutrients, they aren’t needed for the production of biofuels and other commercial biobased products,” said Matt Liebman, professor of agronomy. “These nutrients would be treated as waste materials in the biorefinery, but we are looking at ways to recover them from the conversion process and return them back to the soil.”

Liebman is working with Associate Professor of Agricultural and Biosystems Engineering Robert Anex, Iowa Farm Bureau Director of the Office of Biorenewables Programs, Robert C. Brown, and professors of agronomy, Randy Killorn and Ken Moore. According to Liebman, they are looking at nutrient recycling in a holistic manner by replicating the nearly closed nutrient cycle of integrated crop and livestock systems. These integrated systems, once widespread, use manure as fertilizer and make use of legume plants such as alfalfa and clovers to replace nitrogen in the soil. To help close the nutrient cycle in the case of cellulosic biorefineries, the research team is experimenting with two types of alternative cropping systems, and examining how effectively switchgrass, used Nutrient Recovery from Integrated Cellulosic Biorefineries as a biofuel feedstock, utilizes nutrients recovered from biorefineries. In the process of converting switchgrass and other kinds of biomass into liquid fuels, the researchers hope that nitrogen (as gaseous ammonia) and other nutrients (as ash) can be recovered during the gasification process. The researchers will then assess the impact of applying the recovered materials back to the biomass production plots.

In addition to protecting the quality of the soil, there are other benefits to nutrient recycling, according to Anex. Cycling captured ammonia back to production fields can reduce the need for synthetic nitrogen fertilizer inputs, which would bring down the amount of fossil fuel energy needed to grow biomass feedstocks. Also, when the nitrogen is combined with a substance called agri-char or bio-char that is produced by biorefineries, it creates an attractive soil additive that can significantly increase crop yields, while removing carbon from the atmosphere. Brown estimates that a 250-hectare farm on a char-and-ammonium-nitrate system could sequester 1,900 metric tons of carbon a year.

“We are trying an integrated approach to maximize the efficiency and, therefore, the viability of cellulosic biorefineries: we are trying to evaluate the agronomic value, the [carbon] sequestration value, the economic value, and the engineering,”
said Brown.

This project, which has the potential to bring down energy costs, protect soil quality, and combat global warming, is being funded by the Leopold Center for Sustainable Agriculture, the Iowa State University Plant Sciences Institute, and the University of Iowa Center for Global and Regional Environmental Research.