Life cycle assessment (LCA) was combined with primary data from nine forest harvesting operations in New York, Maine, Massachusetts, and Vermont, from 2013 to 2019 where forest biomass (FB) for bioenergy was one of several products. The objective was to conduct a data‐driven study of greenhouse gas emissions associated with FB feedstock harvesting operations in the Northeast United States. Deterministic and stochastic LCA models were built to simulate the current FB bioenergy feedstock supply chain in the Northeast US with a cradle‐to‐gate scope (forest harvest through roadside loading) and a functional unit of 1.0 Mg of green FB feedstock at a 50% moisture content. Baseline LCA, sensitivity analysis, and uncertainty analyses were conducted for three different FB feedstock types—dirty chips, clean chips, and grindings—enabling an empirically driven investigation of differences between feedstock types, individual harvesting process contributions, and literature comparisons. The baseline LCA average impacts were lower for grindings (4.57 kg CO2eq/Mg) and dirty chips (7.16 kg CO2eq/Mg) than for clean chips (23.99 kg CO2eq/Mg) under economic allocation, but impacts were of similar magnitude under mass allocation, ranging from 24.42 to 27.89 kg CO2eq/Mg. Uncertainty analysis showed a wider range of probable results under mass allocation compared to economic allocation. Sensitivity analysis revealed the impact of variations in the production masses and total economic values of primary products of forest harvests on the LCA results due to allocation of supply chain emissions. The high variability in fuel use between logging contractors also had a distinct influence on LCA results. The results of this study can aid decision‐makers in energy policy and guide emissions reductions efforts while informing future LCAs that expand the system boundary to regional FB energy pathways, including electricity generation, transportation fuels, pellets for heat, and combined heat and power.
There is a lack of widespread interest in slow pyrolysis biochar pathways relative to other bioenergy pathways because of the perceived absence of biochar's market value when produced at a commercial scale. Thus, most refereed techno-economic analyses focus on fast pyrolysis. This study quantifies the carbon price point at which the economic feasibility of the slow-pyrolysis pathway for biochar production is equal to or greater than a fast-pyrolysis pathway for biochar and biofuel production using baseline minimum carbon prices (MCP). These factors are then modeled under uncertainty to generate stochastic cash flows for the calculation of a 20-year net present value and carbon abatement cost probability distributions. This article examines whether a slow-pyrolysis pathway is ever more financially attractive than a fast-pyrolysis pathway at realistic carbon prices. The results show fast pyrolysis to fuels and biochar achieving the lowest baseline MCP of $61.38/Mg, while the slow pyrolysis to biochar and methanol at 450 °C scenario yields the highest baseline MCP of $642.40/Mg. A notable result is the baseline MCP for the slow pyrolysis to biochar scenario achieving $123.48/Mg, when compared with the fast pyrolysis to fuels and electricity scenario, resulting in a baseline MCP of $182.03/Mg. The results suggest that carbon prices, when high enough, can incentivize biochar carbon sequestration produced from slow-pyrolysis pathways rather than carbon abatement with biofuels, and that slow pyrolysis to biochar and methanol scenarios require a higher baseline MCP and are less financially competitive than the other pathways.Techno-economic analysis (TEA) is a comprehensive methodology used to quantify the economic feasibility of cellulosic bioenergy production. 18 Brown et al. conducted a TEA of biobased chemical production via the fast-pyrolysis 596
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