Life cycle assessment of biochar produced from forest residues using portable systems

Abstract

Forest fires are getting extreme and more frequent because of increased fuel loads in the forest and extended dry conditions. Fuel treatment (i.e., thinning) methods to mitigate forest fires will generate large volumes of forest residues together with available logging residues that can be used to produce biochar. It has been proposed that portable biochar systems are economical means to utilize forest residues as an alternative to slash burning. In this study, the environmental impacts of biochar produced from forest residues using three portable systems [1. Biochar Solutions Incorporated (BSI), 2. Oregon Kiln, and 3. Air-curtain Burner] were evaluated using a cradle-to-gate life-cycle assessment approach. Environmental impacts were analyzed considering the various quality of feedstock, biomass collection methods, different production sites, and various sources of power used in the production of biochar. The results illustrate that the global warming potential (GWP) of biochar production from forest residues through BSI, Oregon Kiln, and Air-Curtain Burner were 0.25–0.31, 0.11, and 0.16 tonne CO2eq./tonne of fixed carbon in biochar respectively. Compared to pile burn, biochar production from forest residues with a portable system at the landing, reduced global warming potential (GWP) by 1.92–2.83, 2.7, and 1.9 tonnes CO2eq./tonne of biochar through BSI, Oregon Kiln, and Air-Curtain Burner respectively. The Air-Curtain Burner and Oregon Kiln have minimal feedstock preparation, thus have lower environmental impacts than the BSI system. The BSI system requires feedstock preparation and power to operate the system. The use of the biomass-gasifier generator improved the environmental performance substantially (16–280%) compared with a diesel generator in biochar production. Overall, the net GWP in biochar produced (0.10–1.63 tonne CO2eq./tonne of residues) from forest residues can reduce environmental impacts (2–40 times lower net CO2eq. emissions) compared to slash burning.