Pyrolysis biochar systems for recovering biodegradable materials: A life cycle carbon assessment

A life cycle assessment (LCA) focused on biochar and bioenergy generation was performed for three thermal treatment configurations (slow pyrolysis, fast pyrolysis and gasification). Ten UK biodegradable wastes or residues were considered as feedstocks in this study. Carbon (equivalent) abatement (CA) and electricity production indicators were calculated. Slow pyrolysis systems offer the best performance in terms of CA, with net results varying from 0.07 to 1.25 tonnes of CO2 eq. t−1 of feedstock treated. On the other hand, gasification achieves the best electricity generation outputs, with results varying around 0.9 MWhe t−1 of feedstock. Moreover, selection of a common waste treatment practice as the reference scenario in an LCA has to be undertaken carefully as this will have a key influence upon the CA performance of pyrolysis or gasification biochar systems (P/GBS). Results suggest that P/GBS could produce important environmental benefits in terms of CA, but several potential pollution issues arising from contaminants in the biochar have to be addressed before biochar and bioenergy production from biodegradable waste can become common practice.

► This is a life cycle assessment for three thermal treatment configurations.
► Slow pyrolysis systems offer the best performance in terms of carbon abatement.
► Gasification achieves the best electricity generation outputs.
► Waste treatment practices as reference scenarios have a key influence upon results.
► Results suggest that biochar systems produce important environmental benefits.