New Benchmark For Carbon Credit Modeling, Soil Fertility
The study shows that an acre planted with a bioenergy sorghum hybrid accumulates about 3.1 tons of dry root biomass over the crop’s 155-day growing season. Bioenergy sorghum roots also grew to over 6.5 feet deep over their growing season.
These new metrics make it easier to predict how much atmospheric carbon dioxide might be captured inside roots. The numbers can also shed light on how many carbon credits a planted field might earn.
“Frankly, the numbers are quite favorable,” Rooney said.
The numbers are also important for understanding the crop’s potential to improve soil fertility and water-holding capacity by replenishing soil organic carbon. However, previous research has shown that in the U.S., soil organic carbon levels have fallen by 50% over the past 100 years in land planted with annual crops.
This drop in soil carbon levels could be due to cropping practices, microbial activity and changing land use, Rooney said. These complex factors mean that predicting how long it might take to replenish lost carbon requires sophisticated modeling. The restoration process is likely to take many decades.
“For modeling, they need to have a realistic number to start with,” Rooney said. “We haven’t historically had enough info to do that, but this study provides a benchmark for scientists and policymakers.”
Need For Further Research
In this study, Rooney and his team managed the field trials and helped with phenotyping. Mullet and his team characterized the root system and the genes expressed within.
Over multiple years, the study considered in-depth how one bioenergy sorghum hybrid interacts with two soil types, Rooney said. He stresses the need to conduct further research.
“In this study, we didn’t sample the genetic diversity of bioenergy sorghum at all, except for one standard type,” Rooney said. “And looking at multiple environments and expanding the range of we are evaluating is essential.”
Bioenergy Sorghum As Part Of A Sustainable Bioenergy Production System
Modeling studies estimate that millions of acres of abandoned and marginal cropland in the U.S. are available for planting. Many of those acres are in the Gulf Coast region. The region is ideal for bioenergy sorghum production because of ample rainfall, long growing seasons and low competition with grain crops, Mullet said. Furthermore, the crop has improved over the years in terms of productivity, resilience and composition, thanks to Mullet’s and Rooney’s efforts.
“Recently, I’ve decided the most important thing we can do is continue research on bioenergy sorghum optimization, but also to help design and build biorefineries that will process materials from the crop in a way that’s optimal,” Mullet said.
Carbon captured in biofuels and bioproducts at biorefineries, and by bioenergy sorghum roots could generate carbon credits, potentially benefiting producers and industry.
Yet despite the Gulf Coast’s excellent potential for biofuels production, there are no bioenergy research centers and very few biorefineries in the region, Mullet said.
Therefore, Mullet is now working to attract industry and government funding to help build the next generation of biorefineries designed to use bioenergy sorghum biomass for the production of biofuels, bioproducts and biopower.
“The project has expanded to not just producing biofuels and bioproducts, but also directly capturing carbon and sequestering it,” he said.