Soil and root carbon storage is key to climate benefits of bioenergy crops

Document Type: Research Paper

Authors

1 Key laboratory of the Three Gorges Reservoir Region’s Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400045, China.

2 Key laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian 361021, China.

3 Environmental Studies Program, Dartmouth College, Hanover, NH 03755, USA.

4 Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108, USA.

5 Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106, USA.

Abstract

Most bioenergy feedstock studies focus on maximizing aboveground biomass production. Cropland with fertile soils can produce high aboveground biomass yields but its diversion to bioenergy causes greenhouse gas emissions from direct and indirect land use changes. Here, we analyze three grassland experiments that minimize land use changes by using abandoned and degraded agricultural land. We find that soil and root carbon storage is a greater determinant of the climate change mitigation potential of biofuels than aboveground biomass, and tends to be higher for treatments with high plant diversity. Aboveground biomass yield ranged from 450-650 g ha-2 yr-1 for the productive treatments with moderate intensification, but its climate benefit via converting into biofuels and displacing fossil fuels can be substantially reduced by the rebound effect of fuel market. Because of high soil and root C storage rates (152-483 g CO2 ha-2 yr-1), many treatments are carbon negative even without the fossil fuel displacement benefit. To effectively mitigate greenhouse gas emissions, we should focus on increasing belowground carbon storage and explore the potential benefits of high-diversity plant species mixtures. 

Graphical Abstract

Soil and root carbon storage is key to climate benefits of bioenergy crops

Highlights

  • Perennial grasses grown on degraded and abandoned cropland were analyzed.
  • Soil and root C storage was found to be key to GHG reductions of biofuels.
  • Soil and root C storage rates tend to be higher in high-diversity species mixtures.
  • Climate benefit of aboveground biomass can be reduced by fuel market rebound effect.

Keywords