Life cycle environmental impacts of five technological routes for straw utilisation in China

Whilst five technological routes have been proposed in China and implemented for the comprehensive utilisation of crop straw, as fertilizer, fodder, fuel, basic material, and raw material, respectively, there is still uncertainty regarding their efficiency and environmental performance. This study compared the material flows, environmental impacts, and potential improvements of these five routes using full-scale data in the central region of China. All routes achieved efficient utilisation in terms of total solid with transfer coefficients of 67%similar to 100%, but the fertiliser, fuel and raw material routes required significant amounts of manure and wood chips, respectively, due to the process requirements. On the other hand, the routes producing briquette fuel and board had lower overall loads to the mid-point environmental categories than the others, with product substitutions leading to the highest savings in terms of climate change (-1330 kg CO2-eq/t and -311 kg CO2-eq/t, respectively). The fertiliser route performed differently in terms of toxic and non-toxic impact categories, with use-on-land of compost contributing -162 kg CO2-eq/t savings to climate change impacts by carbon sequestration and fertilizer substitution, and at the same time introducing N, P and trace metal pollution. According to the parameter sensitivity analysis, even slight reductions in material and energy consumption could lead to varying degrees of improvement in carbon reduction. Overall, the findings of this study provide quantitative evidence for the selection of appropriate technologies and the sustainable utilisation of crop straw, by maximizing the benefits of crop straw utilisation while minimizing its negative effects to the environment.