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Replacing fossil fuels with biofuels offers a promising path to decarbonizing the transportation sector, a major source of greenhouse gas emissions (GHGs). Utilizing waste biomass such as forest residues is particularly appealing, as it avoids land-use change and associated GHG emissions. Current biofuel life cycle assessment (LCA) adopted by regulatory agencies considers forest residues as carbon-neutral feedstock and typically ignores soil organic carbon (SOC) changes from residue removal. Our study quantifies SOC change caused by removing forest residues in the Southern US and found that they can make a substantial contribution to the carbon footprint of biofuel derived from forest residues. Our results emphasize the need to include soil carbon assessment in future LCAs, biofuel policy, and forest management, even when waste biomass is used and no land-use change is involved.
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Dynamic life-cycle carbon analysis for fast pyrolysis biofuel produced from pine residues: implications of carbon temporal effects
Abstract BackgroundWoody biomass has been considered as a promising feedstock for biofuel production via thermochemical conversion technologies such as fast pyrolysis. Extensive Life Cycle Assessment studies have been completed to evaluate the carbon intensity of woody biomass-derived biofuels via fast pyrolysis. However, most studies assumed that woody biomass such as forest residues is a carbon–neutral feedstock like annual crops, despite a distinctive timeframe it takes to grow woody biomass. Besides, few studies have investigated the impacts of forest dynamics and the temporal effects of carbon on the overall carbon intensity of woody-derived biofuels. This study addressed such gaps by developing a life-cycle carbon analysis framework integrating dynamic modeling for forest and biorefinery systems with a time-based discounted Global Warming Potential (GWP) method developed in this work. The framework analyzed dynamic carbon and energy flows of a supply chain for biofuel production from pine residues via fast pyrolysis. ResultsThe mean carbon intensity of biofuel given by Monte Carlo simulation across three pine growth cases ranges from 40.8–41.2 g CO2e MJ−1(static method) to 51.0–65.2 g CO2e MJ−1(using the time-based discounted GWP method) when combusting biochar for energy recovery. If biochar is utilized as soil amendment, the carbon intensity reduces to 19.0–19.7 g CO2e MJ−1(static method) and 29.6–43.4 g CO2e MJ−1in the time-based method. Forest growth and yields (controlled by forest management strategies) show more significant impacts on biofuel carbon intensity when the temporal effect of carbon is taken into consideration. Variation in forest operations and management (e.g., energy consumption of thinning and harvesting), on the other hand, has little impact on the biofuel carbon intensity. ConclusionsThe carbon temporal effect, particularly the time lag of carbon sequestration during pine growth, has direct impacts on the carbon intensity of biofuels produced from pine residues from a stand-level pine growth and management point of view. The carbon implications are also significantly impacted by the assumptions of biochar end-of-life cases and forest management strategies.
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- PAR ID:
- 10308150
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Biotechnology for Biofuels
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 1754-6834
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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