Can straw recycling achieve sustainable agriculture at the smallholder level? A case in a semi-arid region

Diversified straw recycling practices are essential to achieve sustainable agriculture at the smallholder level. This study comprehensively evaluated the sustainability of two straw recycling models, agro-pastoral-biogas (CCBS) and carbonization (CBBS). The findings demonstrated that the economic indicators (such as spring maize yield and net economic benefits) accounted for a larger proportion of the total score in the CCBS model, indicating that the model is more sustainable for promoting smallholder economic income, while the CBBS model performed even better in carbon sequestration and emission reductions. These results were attributed to the more notable increase in spring maize productivity and the addition of two production units, fattening and biogas digester. However, the sustainability of the CCBS model declined as the straw recycling chain lengthened; the CBBS model had the highest sustainability index. Specifically, maize grain yield and SOC storage increased by 3.86%-11.7% and 11.66%-36.07%, respectively, and soil GHG emissions increased by 20.57% and decreased by 59.9%, respectively, for both models. Despite the substantial economic or environmental benefits, neither model can achieve the win -win goal of sustainability. We conservatively recommend the CCBS model and suggest more specialized smallholder production, but call for more interventions to optimize the CCBS model, as it encompasses multiple development objectives, such as combining planting and breeding, energy substitution, and carbon sequestration -emission reduction, which is more in line with the aspirations of smallholders and other groups.