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

Abstract

To shift towards low fossil carbon economies, making more out of residual streams is increasingly promoted. Yet, it remains unclear whether or not deploying advanced reuse of residual biomass really achieves net environmental benefits compared to current management practices. By integrating resource assessment methods, consequential life cycle analysis 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), principally due to current crop residues and livestock effluent management practices which generate more than 90% of total environmental impacts and associated uncertainties. We systematically characterize the environmental impacts for each stream, by reporting potential improvement measures as well as actions to reduce uncertainties. Overall, current reuse of residual streams in agronomy is estimated to meet more than half of total French P and K fertilizing demand, but only around 6% for nitrogen due to current volatilization and farming accounting practices. Moreover, only 3% of residual streams are currently supplying an energy service. We believe the current situation is not a suitable reference for bioeconomy trajectories. There are already efforts underway to improve the agricultural reuse and energy recovery of these streams. These initiatives aim to reduce the baseline and prioritize the use of biogas in sectors without decarbonization options, potentially halving the residual impact. Accordingly, 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 relevance of bioeconomy strategies, but should include refined modeling and move towards spatially-explicit LCA to accompany local waste management planning.