Bioenergy Crop Systems and Soil Carbon Dynamics

Bioenergy crops, spanning annual species such as maize and perennial grasses or woody crops like switchgrass and willow, are cultivated to produce renewable fuels and reduce net greenhouse gas emissions. Their impact on soil carbon dynamics is determined both by the inherent biology of the crop and the management practices applied. Perennial systems often develop extensive root networks, which foster greater inputs of organic matter and promote the long-term accrual of soil organic carbon (SOC) at depth. In contrast, conventional annual cropping typically involves tillage and repeated soil disturbance, accelerating microbial decomposition of existing SOC and resulting in net carbon losses over time. Site characteristics, including soil texture, climate and bulk density, further modulate soil carbon responses, while rhizosphere priming effects can either enhance or offset carbon gains by stimulating microbial activity around roots. Longitudinal studies have demonstrated that cash-grain and alfalfa systems may lose between 0.5 and 0.8 Mg C ha⁻¹ yr⁻¹, whereas restored prairies and rotational grazing preserve or even augment SOC stocks. Conversely, planting bioenergy feedstocks on high-carbon peat soils can trigger large CO₂ emissions, potentially undermining climate mitigation benefits. An integrated understanding of crop selection, land-use history and soil management is thus essential for optimising bioenergy systems as a genuine carbon sink while satisfying biomass supply and ecosystem service objectives.

Research from Nature Portfolio

Recent studies have illuminated key trade-offs in bioenergy cropping at field scale. One study reported that cultivating maize for biomethane on drained peat soils yields soil CO₂ emissions up to three times greater than equivalent natural gas, emphasising the need to account for soil-borne emissions in lifecycle assessments. Another long-term investigation over 30 years in a temperate Mollisol revealed that perennial grasslands and rotationally grazed pastures maintained full-depth SOC stocks, while cash-grain and alfalfa systems lost carbon at rates approaching 0.8 Mg C ha⁻¹ yr⁻¹. By incorporating bulk-density corrections and deep-profile measurements, this work underlined the inadequacy of row-crop systems for sustained SOC sequestration and the value of well-managed perennial bioenergy systems in stabilising soil carbon in productive agricultural landscapes.

Bioenergy Crop Systems and Soil Carbon Dynamics publication trend

The graph below shows the total number of articles in bioenergy crop systems and soil carbon dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Bioenergy crop systems: Agricultural regimes using dedicated plant species to produce biomass for renewable energy.

Soil organic carbon (SOC): The carbon component of organic compounds within the soil, originating from plant and microbial residues.

Perennial crops: Plant species that live for multiple years, developing deep root systems that enhance soil carbon inputs.

Annual crops: Plant species grown for a single season, often involving tillage that can accelerate SOC decomposition.

Carbon sequestration: The long-term storage of carbon in terrestrial reservoirs, notably in soil organic matter.

Bulk density: The mass of dry soil per unit volume, including pore spaces, used to convert carbon concentrations into stocks.

References

1. Biomethane produced from maize grown on peat emits more CO2 than natural gas. Nature Climate Change (2024).
2. Soil carbon maintained by perennial grasslands over 30 years but lost in field crop systems in a temperate Mollisol. Communications Earth & Environment (2024).
3. Impact of bioenergy feedstock carbon farming on sustainable aviation fuel viability in the United States. Proceedings of the National Academy of Sciences of the United States of America (2023).
4. Soil organic carbon stock change following perennialization: a meta-analysis. Agronomy for Sustainable Development (2023).
5. Changes in soil organic carbon under perennial crops. Global Change Biology (2020).