Consequential Life Cycle Assessment of Biochar Comparing Different Biochar Production and Application Pathways

Abstract

Biochar fights climate change, in addition to a range of possible environmental benefits. However, widespread adoption is lacking. This is partly due to policymakers' and end users' lack of confidence in biochar's effects. It does not help that biochar is diverse – many types can be produced by changing the feedstock and production conditions – and versatile – it can be used in many applications. In an attempt to improve decision-making given the diversity and versatility, this research investigates two types of biochar in two applications. The biochars are produced from the woody fraction of green waste and from chicken manure. One application is biochar's direct use as soil amendment, whereas the other is a cascading use of biochar. The latter means it is first used in anaerobic digestion before being applied to land (mixed in the digestate). This research aims to determine whether diverting biomass for biochar has a positive environmental impact and, if yes, to identify the scenario (biochar and application) with the biggest environmental gain. We do this using a consequential life cycle assessment (LCA). Based on preliminary results, using the biomass to produce biochar provides an environmental gain compared to the current use. Furthermore, the cascading use of biochar provides a greater gain than the direct field application. It is expected that the sensitivity and uncertainty analyses will provide new insights into the dynamics of the environmental impact of the different systems. To our knowledge, this is the first LCA of biochar that simultaneously compares feedstocks and applications. Furthermore, the number of consequential LCAs of biochar is limited.