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This study assessed the cradle-to-grave life cycle greenhouse gas (GHG) emissions of ethanol production via the fermentation of sugars derived from hot water extraction (HWE) of forest biomass under two processing energy scenarios (biomass, natural gas). The energy source was a key driver of the climate change benefits of ethanol production. Compared to petroleum gasoline, the lifecycle GHG emissions of ethanol fuel were 78% lower for the biomass scenario while the natural gas scenario resulted in 2% increase of GHG. Monte Carlo analysis revealed that when the input variable parameters were allowed to vary by 20% from their baseline value, the biomass scenario was always compliant with the 60% GHG reduction requirement for cellulosic ethanol. Measures to improve the energy efficiency of the biorefinery per unit of ethanol produced (i.e. increase ethanol yield or reduction in energy consumption) could result in ethanol fuels produced under the natural gas scenario with GHG emissions equal to or less than those of petroleum gasoline. The potential for ethanol from forest biomass in the Northeast United States to contribute to the decarbonization process is heavily dependent on the process energy resources chosen to power the biorefinery and the characteristics of the designed conversion process. [Display omitted] • Carbon footprint of ethanol from forest biomass hot water extract was assessed. • A natural gas and a biomass scenario for process energy were defined. • Biomass scenario resulted in low carbon biofuels with 78% less GHG than gasoline. • Natural gas scenario emitted 2% more GHG emissions than gasoline. • The most influential parameters included ethanol yield and energy needed for HWE. [ABSTRACT FROM AUTHOR]

Abstract Bulk density is a key attribute of biomass feedstocks that affects both conversion processes and logistics. Reported bulk density for fresh willow chips ranges between 195 and 393 kg m−3 and it is unknown if standardized methods using several kg of chips scale effectively to collection vehicles that contain several Mg. The objective of this study was to compare three bulk density methods for 53 commercially harvested willow loads and compare bulk density in three different collection wagons. An ISO standard 'bucket' method was compared to actual and effective bulk density measurements. Mean as-received bulk density using the standard ISO method was 262 kg m−3 (σ = 25) and was not correlated with wagon load measurements of actual or effective bulk density. The actual bulk density in a small (10 m3) collection vehicle was 302 kg m−3 (σ = 32), which was significantly greater than the 214 kg m−3 (σ = 28) that was measured in two larger (30 m3) collection vehicles. In addition, actual bulk density in wagons was higher than the effective bulk density (247 kg m−3 (σ = 24)) observed for the truck deliveries. Collection wagon geometry and design impacted these results, which may have implications for modeling these systems. The variation in bulk density values is important to understand and represent in modeling of harvesting and logistics systems in order to capture what is actually occurring in commercial scale operations. Highlights • Bulk density (BD) values available in the literature cover a wide range. • BD of shrub willow biomass was determined using three methods. • BD measured in commercial wagons did not match BD values from standardized methods. • Willow BD in collection wagons was influenced by size and geometry of dump bodies. • Effective BD may be an adequate surrogate for actual BD in commercial vehicles. [ABSTRACT FROM AUTHOR]