New study shows producers where and how to grow cellulosic biofuel crops
January 16, 2018, University of Illinois at Urbana-Champaign
Mixed herbaceous energy crops grown on Conservation Reserve Program land did not yield as well as other production systems. Credit: Lauren Quinn
According to a recent ruling by the United States Environmental Protection Agency, 288 million gallons of cellulosic biofuel must be blended into the U.S. gasoline supply in 2018. Although this figure is down slightly from last year, the industry is still growing at a modest pace. However, until now, producers have had to rely on incomplete information and unrealistic, small-scale studies in guiding their decisions about which feedstocks to grow, and where. A new multi-institution report provides practical agronomic data for five cellulosic feedstocks, which could improve adoption and increase production across the country.
“Early yield estimates were based on data from small research plots, but they weren’t realistic. Our main goal with this project was to determine whether these species could be viable crops when grown on the farm scale,” says D.K. Lee, associate professor in the Department of Crop Sciences at the University of Illinois and leader of the prairie mixture portion of the study.
The project, backed by the U.S. Department of Energy and the Sun Grant Initiative, began in 2008 and includes researchers from 26 institutions. Together, they evaluated the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures in long-term trials spanning a wide geographical area. Due to shortages in plant materials, Miscanthus and energycane were grown on smaller plots than the other crops, but researchers say the new results are still valuable for producers.
“Although making real-world decisions and recommendations based on performance data from small plots is less desirable than from field-scale plots, we feel comfortable with the Miscanthus results since they were based on 33 data sets collected from five sites over seven years,” says Tom Voigt, professor in the crop sciences department at U of I and leader of the Miscanthus portion of the study.
Crops were grown for five to seven years in multiple locations and with varying levels of nitrogen fertilizer. Although most of the crops are known to tolerate poor soil quality, the researchers found that they all benefitted from at least some nitrogen. For example, Miscanthus did best with an application of 53.5 pounds per acre.
“When we didn’t fertilize with any nitrogen, yields dropped over time. But if we used too much, 107 pounds per acre, we were increasing nitrous oxide emissions and nitrate leaching,” says Voigt. “There is some need for fertilization, but it should be tailored to specific locations.”
Prairie mixtures, which were grown on land enrolled in the Conservation Reserve Program (CRP), also benefitted from added nitrogen. Yield kept increasing with the addition of up to 100 pounds per acre, but Lee says producers would have to weigh the yield benefit against the cost of the fertilizer.
“Even though it increased yield, it is economically not profitable to use more than 50 pounds of nitrogen per acre.”
And although most of the crops are somewhat drought-tolerant, precipitation made a difference.
“Miscanthus production was directly related to precipitation,” Voigt says. “In areas where precipitation was down, yields generally dropped. However, it did depend on timing. If there was a good amount of water in the winter, plants could get going pretty well in the spring. But if we had little rainfall after that, that hurt yields.”