Setting the environmental performance threshold for diverting residual streams towards bioeconomy strategies

Abstract

Abstract To shift towards low fossil carbon economies, making more out of residual biomass is increasingly promoted. Yet, it remains unclear if implementing advanced technologies to reuse these streams really achieves net environmental benefits compared to current management practices. By integrating resource assessment methods, consequential life cycle analysis (LCA) and uncertainty analysis, we propose a single framework to quantify the residual biomass baseline, which is the environmental threshold any bioeconomy strategy should overpass. For France, we estimate the residual biomass baseline to generate 18.4 ± 2.7 MtCO2-eq.y-1, 255 ± 35 ktN-eq.y-1 and 12,300 ± 800 diseases per year (particulate matter formation). More than 90% of total environmental impacts and associated uncertainties were found attributable to the conventional management of crop residues and livestock effluents. We systematically assessed the environmental impacts associated with each residual stream, by reporting potential improvement measures and actions to reduce uncertainties. Overall, reusing residual streams as fertilizing products is currently supplying more than half of total P and K demand for France, but only 6% of the nitrogen demand, due to volatilization and prevailing farming accounting practices. Moreover, only 3% of residual streams are currently diverted to energy recovery. We argue that current situation is not a suitable reference for bioeconomy trajectories, as efforts to improve the agricultural and energy reuse of residual streams are already underway. These include the wide deployment of anaerobic digestion and the prioritization of biogas to suply sectors without decarbonization options, among others. We suggest any alternative bioeconomy strategy should rather compare to this projected baseline, estimated for France at 8.5 MtCO2-eq.y-1. The proposed framework is a stepping stone in defining indicators tailored to track the environmental relevance of bioeconomy strategies, but should be integrated with spatially-explicit LCA to guide local waste management planning.