Research objectives Perform LCA on Willow-based Ethanol fuel to evaluate the following: • Global warming potential (GWP) • Fossil energy use • Water use • Other impacts such, toxicity, acidification, and photochemical-oxidants formation To improve the environmental fuel’s performance with contributional analysis.
ScopeBiomass production Biomass transport Biochemical conversion (core process)Fuel distribution Fuel use
Key assumptions Land use does not cause direct or indirect greenhouse gas emissions. • Direct emissions for site preparation are offset by below ground accumulation. • Use of idle land minimizes indirect land use Feedstock and final products are transported 100 miles (average round trip). Electricity from biorefinery displaces production from US national grid – no regional specificity. Gypsum is disposed of as a solid by-product Comparisons with gasoline are on an equivalent energy (MJ) basis System expansion used to model impacts of co-products
Willow Biomass Production Cycle Three-year old after Site Preparation coppicePlanting One-year old after coppice CoppiceFirst year growth Early spring after coppicing
Willow Production & Harvesting The largest inputs in terms of energy and dollars are: harvesting site preparation and establishment N fertilizer inputs Crop is not irrigated Willow harvested using single pass cut and chip system Chips are blown into a forage or dump wagon and sent right to the biorefinery
Process area Process Yields Value Unit Pretreatment Xylan to Xylose Yield 75 % Mannan to Mannose Yield 61 % Galactan to Galactose Yield 61 % Arabinan to Arabinose Yield 75 % Saccharification Cellulose to Glucose Yield 75 % Co-Fermentation Glucose to Ethanol Yield 95 % Xylose to Ethanol Yield 85 % Arabinose to Ethanol Yield 85 % Mannose to Ethanol Yield 95 % Galactose to Ethanol Yield 95 % Contamination Loss 3 %Overall Yield = 74 gallons ethanol/ton (OD biomass)
MethodologyBiomass SimaPro LCAgrowth/yield model GREET vehicle-use(by CORRIM) model (by UW) model (by ANL) ASPEN process model (by NREL and UW)
Global Warming Potential (GWP)
Fossil energy use
Conclusions Production of ethanol from willow plantations is near carbon neutral • Displacement of power production from coal and oil • No accounting for indirect land use Water usage for bioconversion is substantial and will need to be addressed Other impacts are mixed –much greater for ethanol (acidification) for some and greater for petroleum(toxicity) for others
AcknowledgementThe support for this research from the US Forest Service andthe Department of Energy is greatly appreciated.
Willow – excellent feedstock for bioconversion processes Example SRWC (Short Rotation Woody Crop) Rapid early growth rates Ease of vegetative propagation from dormant cuttings. Ability to re-sprout after multiple harvests. Suitable for cultivation on low quality land. Broad genetic diversity Good “sugar release”
Agrochemical Combustion CO2 Offgas emissions emissionsSYSTEMBOUNDARIES Fossil fuels production S1: Willow production and collection subsystem Lubricants production Planting Harvesting Chipping Fertilizers production CO2 Pesticides production S2: Ethanol biorefinery subsystem Water Willow chips Gypsum Landfill Feedstock handling Pretreatment & Conditioning Distillation & Dehydration Chemicals production Syrup & solid residues Saccharification & Co-fermentation Ethanol Enzyme production Storage Wastewater treatment conditioning Sludge & biogas Nutrients production Energy production Electricity Steam Utilities Avoided US mix electricity production Landfill Excess electricity Ash S3: Ethanol distribution S4: Ethanol use subsystem Fossil fuels production subsystem