Land-use change and straw removal in sugarcane cultivation: a meta-analysis of soil carbon stocks

Increasing biofuel production is crucial to accelerating the energy transition and mitigating climate change. However, the impact of land-use change (LUC) and management practices on soil organic carbon stocks (SOCs) must be considered when assessing the true greenhouse gas (GHG) cost of biofuels. Here, we conducted a meta-analysis (474 pairwise observations) to obtain Brazil's SOCs change factors (SOCscf) for LUC and management practices in sugarcane fields. We found that native vegetation conversion to sugarcane reduced the SOCs in all assessed periods. Annual crops conversion to sugarcane reduced SOCs in the early years but increased after 20 years. Converting pastureland to sugarcane reduced SOCs only in the 10- to 20-year period, with no change observed in the other evaluated periods. However, its high SOCscf variability is probably related to pasture degradation levels, suggesting an increase in SOCs when conversion occurs from degraded pastures. Straw management, one of the main practices that impacts SOCs in sugarcane fields, did not affect it at low removal rates (< 34%). Meanwhile, moderate (34-66%) and high (> 66%) removal resulted in losses of 5.0% (SOCscf 0.950) and 9.9% (SOCscf 0.901), respectively.  Ultimately, we emphasise that our results could inform the development of improved public policies and be incorporated into future life cycle assessment (LCA) and modelling studies.  They provide reliable data on the regional SOCscf induced by LUC and straw removal, enhancing the accuracy of the carbon footprint assessment of biofuel production.