Biochar replaces peat in horticulture: Environmental impact assessment of combined biochar & bioenergy production
Fryda L, Visser H J M, Schmidt J (2019)
This study evaluates the environmental impact of replacing natural gas heating and peat use in the horticulture substrate market by means of biomass ga,sification towards co-production of syngas and biochar. The produced syngas can provide sustainable greenhouse heating; biochar is currently considered as a peat substitute while it offers carbon sequestration potential when disposed in the soil due to its higher carbon recalcitrance compared to peat. The carbon footprint of four feedstocks is followed, namely willow and pine from tree nurseries, grade A wood pellets produced from demolition wood and park residues. The CO2 emissions timing is taken into account (time delay between harvest, decay and growth rates of organic matter, peat and biochar). Emission calculations from indirect land use changes (iLUC) are included for the two wood feedstocks (willow and pine). The feedstock source and physical properties have a high share in the environmental impact of the bioenergy production (process heat) and biochar. Peat replacement by biochar reduces the current pressure on the environment caused by peat extraction and use. When biochar is stored permanently in the soil as a disposal option, the corresponding negative CO2 flux further reduces the total CO2 emissions acting as a carbon capture and storage mechanism.