Many U.S. farms contain fields or portions of fields where growing grains such as corn isn’t profitable.
Maybe the soil is too infertile or maybe the drainage isn’t right. Regardless, crop values in some areas are low enough that it costs more to plant and harvest the crop than the farmers earn when they sell it.
Idaho researchers say the burgeoning bioenergy industry could offer a solution: planting energy crops—plants such as sorghum, switchgrass and miscanthus—instead of grain on those underperforming parts of fields.
Not only could energy crops help make these unprofitable lands profitable, said Shyam Nair, an environmental scientist at Idaho National Laboratory, but they could also provide a much-needed source of biomass to make biofuels, biopower and bioproducts.
The findings are published in the journal BioEnergy Research.
To reach their conclusions, Nair and his co-authors used the Landscape Environmental Assessment Framework (LEAF) computer software developed at INL for the U.S. Department of Energy.
The LEAF software integrates several different computer models designed to estimate soil, soil carbon, and nitrogen losses via wind and water erosion and other important indicators of field sustainability and productivity.
The result is site-specific landscape performance assessments that allow land managers to make more informed decisions about how they grow plants for food, feed, fiber and fuel.
Nair, his colleagues and a company called AgSolver used LEAF to analyze whether planting energy crops would improve profitability and environmental sustainability. They started by gathering agriculture data from four U.S. counties through sources such as the USDA’s Natural Resources Conservation Service.
Researchers then divided fields into smaller chunks—called subfields—and assessed profitability of grain production. On unprofitable subfields, researchers modeled the impact of energy crops. On profitable subfields, farmers would continue to grow grain and harvest corn stover (the leftover leaves, cobs and stem of corn plants) and other crop residues.
The LEAF software is able to help evaluate how much stover and other crop residues farmers can remove from the field before it has an impact on soil health or the environment. Corn stover could provide significant amounts of biomass feedstock to an expanding bioeconomy.
The researchers found that farmers in those four counties could significantly increase their annual biomass production — from nearly double to 21 times more — by planting energy crops on unprofitable land.
To fully achieve the gains highlighted in the paper, farmers would need to adopt precision agriculture — an approach where crops are monitored on field and subfield levels and the data are used to respond to crop variability.
“Part of the analysis was simulating harvest in these cookie-cutter-shaped fields,” said co-author Damon Hartley, a biofuels and renewable energy researcher at INL. “We simulated equipment movement through the fields and how it would have to move to harvest the entire field.”
Precision agriculture may require smaller or modified harvesting equipment, Hartley said.
Energy crops not only grow well under marginal conditions, they also could provide an environmental benefit.
Such crops require less fertilizer and take up nutrients that might otherwise be washed into surface water or groundwater. Further, stalks and roots of energy crops are typically left behind after harvest, providing a buffer against soil erosion and leaving more carbon in the soil.
“We not only have to look at profitability of the farmer, but also if the process is sustainable,” Nair said.
By growing energy crops on land that isn’t currently profitable, the impact on food production is far less than if energy crops were grown on highly productive land.
“The goal is to find a balance between food production and energy crop production,” Nair said.
If growing energy crops alongside grain becomes widespread, biomass production in the United States could increase enough to meet the DOE’s goal of $84 per ton average logistics price (which includes payment to the grower, preprocessing, handling, harvesting and transportation). Analysts estimate that this price would help biofuels become competitive with fossil fuels.
The recent findings suggest that a large-scale U.S. bioenergy industry could provide economic, social and environmental benefits, but there’s still work to do, Nair and Hartley said. Their next step is to look at how planting energy crops on subfields affects biomass quality, a set of factors including moisture content that impacts biomass processing and conversion to biofuels at the refinery.