Post on 22-Jan-2015
description
Life Cycle Assessment (LCA)
of
Ethanol Fuel from Willow Biomass
CORRIM
Mohit Rastogi, Rick Gustafson, Joyce Cooper, Timothy Volk,
Jesse Caputo, Leonard Johnson, Maureen Puettmann
CORRIM Biofuels Research
• Gasification
• Pyrolysis
• Bioconversion
Ethanol
Pyrolysis Oil
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.
Scope
Biomass transport
Biochemical conversion
(core process)
Fuel distribution Fuel use
Biomass production
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
coppice
One-year old after
coppice
Coppice
First year growth
Site Preparation
Planting
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
Biochemical conversion process
SO2 Steam Lime H2SO4 Gypsum Nutrition
Enzyme
Steam
Burner/Boiler/ Turbogenerator
Utilities
Feedstock storage &
Handling
Storage
Saccharification &
Co-Fermentation
Product purification Wastewater
Treatment
Pretreatment and
Conditioning
Feedstock (Willow)
Nutrition Vent
Steam
Electricity
Boiler blowdown
Anaerobic, CH4
Still solids and evaporator syrup Ethanol
Broth
Excess condensate
Recycle condensate
Cooling tower blowdownn
Recycle water
Steam
(34 MGPY)
(Excess electricity:
~ 20 MW)
(462,000 ton/year)
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)
Methodology
SimaPro LCA
model (by UW)
Biomass
growth/yield model
(by CORRIM)
ASPEN process model
(by NREL and UW)
GREET vehicle-use
model (by ANL)
RESULTS
Global Warming Potential (GWP)
Water use
Fossil energy use
Other Impacts
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
Acknowledgement The support for this research from the US Forest Service and
the 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”
Chemicals production
Nutrients production
Harvesting Chipping
Feedstock handling Pretreatment &
Conditioning
conditioning
Distillation & Dehydration Saccharification &
Co-fermentation
Enzyme production
Storage
Energy production
Wastewater treatment
Utilities Electricity Steam
Landfill
Landfill
S1: Willow production and collection subsystem
S2: Ethanol biorefinery subsystem
S3: Ethanol distribution
subsystem
Water
CO2
Sludge & biogas
Ethanol
Sy
rup
& s
oli
d r
esid
ues
Lubricants production
Ash
Gypsum
Offgas CO2 Combustion
emissions
Willow chips
Avoided US mix
electricity production
Planting
Fertilizers production
Fossil fuels production
Pesticides production
Agrochemical
emissions
Excess electricity
Fossil fuels production
S4: Ethanol use subsystem
SYSTEM
BOUNDARIES
Contribution analysis for Ethanol (Other Impacts)