Life Cycle Assessment of Integrated Biorefinery- Cropping Systems: All Biomass is Local Seungdo Kim...
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Transcript of Life Cycle Assessment of Integrated Biorefinery- Cropping Systems: All Biomass is Local Seungdo Kim...
Life Cycle Assessment of Integrated Biorefinery-
Cropping Systems: All Biomass is Local
Seungdo Kim and Bruce E. Dale
Michigan State UniversityJune 24 - 25, 2004June 24 - 25, 2004Arlington, VirginiaArlington, Virginia
Biocommodities: A New Partnership between the U. S. Chemical Industry & U. S. Agriculture?
Raw Materials + Processing = Value-Added Products
Processing by Physical, Thermal, Chemical and/or Biological Means
Cost to make mature, commodity products depends on:
1) Raw material cost (60-70% of total)2) Processing cost (the remainder)
Features of a Mature Biocommodity Industry: Some Lessons from Petrocommodities
• Yield of product(s) is the dominant techno-economic factor
• Raw material cost & supply ultimately determines potential scale of industry
• Product slate diversifies over time• Very broad plant raw material base (but
compositionally materials are quite similar)• Agricultural productivity (“food vs. fuel”) is the
ultimate constraint on production• “Sustainability” is the dominant socio-environmental
constraint: soil fertility first of all• Industry will be influenced to an unprecedented
degree by local issues: “all biomass is local”
Cost of Biomass vs Petroleum
020406080
100120140160180
5 10 15 20 25
Cost of oil, $/barrel
Cos
t of
bio
mas
s, $
/ton Weight only
Energy content
Some Perspectives and Premises on Agriculture as a Producer & Consumer of Energy
• Inexpensive plant raw materials will catalyze the very large scale production of fuels from “biomass”
• “Consumer of energy” is straightforward• “Producer of energy” not so straightforward
– Except for windpower, agriculture does not “produce” energy– Conversion facility (“biorefinery) makes the energy products
• Systems questions addressed by “life cycle analysis” (LCA) integrating agricultural sector with biorefinery
• Some critical issues: – all BTU are not created equal– “exchange rate” 3
BTU coal = 1 BTU electricity– all BTU do not have the same strategic importance– “All Biomass is Local” climate, soils, crops
What Are Life Cycle (LCA) Models?
• Full system studies of material/energy inputs & outputs of both products & processes • Inventory environmental impacts of products & processes (many possible impacts, select “key” ones)• Objectives:
– Benchmark, evaluate & improve environmental footprint– Compare with competition– Comply with regulations or consumer expectations?
• Methods for doing LCA studies are not universally agreed upon—allocation issues in particular are both important and somewhat controversial
Some Life Cycle Analysis Standards: In Plain English
• Use the most recent data possible• Make it easy for others to check your data
and methods= transparency• Set clear system boundaries: what exactly
are we comparing?• Multi-product systems must allocate
environmental costs among all products-(no environmental burdens assigned to wastes)
• Perform sensitivity analysis: how much do results vary if assumptions or data change?
Our Approach to Life Cycle Analysis
• Be very specific about the location and particular cropping systems that support the biorefinery
• Be very clear and careful about system boundaries
• Defend/explain allocation of environmental burdens among products-including energy products
• Formulate, ask and answer specific questions
• Explore complete system (Industrial Ecology model) when possible
• Remember: “All Biomass Is Local”
Advantages of a Local Focus for Biobased Products LCA
• Reduces opportunities for agenda-driven manipulation of data
• Studies are more relevant to the actual situation faced by investors & innovators
• Better application of agricultural & environmental policy instruments
• Improves selection of crops & cropping systems for local biorefineries
• Illuminates opportunities for system integration & “waste” utilization
Objectives
• Environmental performance of biobased products– Integrated biorefinery-cropping systems
• Ethanol• Polyhydroxyalkanoates (PHA)
• Eco-efficiency analysis– Ethanol and PHA are produced from the
same unit of arable land
Concept of Biorefinery
•Fuels
•Chemicals, etc.
•Monomers
•Lubricants
•Polymers
•Feeds & Foods
•Electricity
•Fertilizer
•Steam
Plant RawPlant RawMaterialMaterial
Pre-Pre-processingprocessing
Final Final ProcessingProcessing
Functional Functional UnitUnit
Recycle or Recycle or DisposalDisposal
Crop Residues
Oilseeds
Sugar Crops
Woody & Herbaceous
Crops
Grains
Protein
Oil
Lignin
Ash
Carbohydrates
Syngas
Products to Replace
Petroleum Based or
PetroleumDependentProducts
Recycledwithin
Product System
orto OtherProduct Systems
Compost pile or
Landfill
Cropping Systems
• Cropping site: Washington County, Illinois• No-tillage practice• Continuous cultivation (No winter cover crop)
– 0 % of corn stover removed: CC – Average 50 % of corn stover removed: CC50
• Effect of winter cover crop – Wheat and oat as winter cover crops after corn
cultivation with 70 % corn stover removal: CwCo 70
Products in a Biorefinery AgriculturalAgricultural
processprocess BiorefineryBiorefinery ProductsProducts UseUse
Corn grain
Corn stover
Corn grain
Wet milling
Corn stoverprocess
Wet milling
PHA fermentation& recovery
•Corn oil•Corn gluten meal•Corn gluten feed
•Ethanol•Electricity
•PHA
Liquid fuel
Edible oil
Animal feed
Export to power grid
Polymer
If applicable
•Ethanol
•Corn oil•Corn gluten meal•Corn gluten feed
Corn stoverCorn stover
process
•PHA
If applicable
Ethanol production systemEthanol production system
PHA production systemPHA production system
•Electricity
Life Cycle Assessment Study
• Functional Unit: One acre of farmland• Allocation: System expansion approach
– Avoided product systems• Gasoline fueled vehicle for ethanol fueled vehicle• Polystyrene for PHA• Corn grain and nitrogen in urea for corn gluten meal/corn gluten feed• Soybean oil for corn oil• Electricity generated from a coal-fired power plant for surplus electricity
• Inventory data sources: Literature– Soil organic carbon and nitrogen dynamics: DAYCENT model
• Impact assessment: TRACI model (EPA)– Crude oil consumption, Nonrenewable energy, Global warming
Primary Assumptions• Ethanol yield
– From corn grain: 2.55 gal/bushel (via wet milling)– From corn stover: 89.7 gal/dry ton
• Ethanol is used as an E10 fuel in a compact passenger vehicle– a mixture of 10 % ethanol and 90 % gasoline by
volume
• PHA yield– From corn grain: 10.9 lb of PHA/bushel– From corn stover : 294 lb of PHA/dry ton
• PHA replaces an equivalent mass of petroleum based polymer.
Allocation Procedures
Corn oil
Corn grainCorn gluten meal
Corn gluten feed
PHA
Soybean oil
Conventional polymer
Soybean milling Soybean culture
Corn culture
Polymer production
ProductsProducts Alternative product systemsAlternative product systems
Crude oil
Nitrogen in urea Ammonia Natural gas
Driving by E10 fueledvehicle
Driving by gasolinefueled vehicle
Crude oilGasoline
Ethanol production systemEthanol production system
PHA production systemPHA production system
Surplus electricity Electricity Coal-fired power plant Coal
Coproduct systems in both production systemsCoproduct systems in both production systems
Primary Products from Biorefineries
Unit CC CC50 CwCo70
Ethanol production
Ethanol from corn grain (A) gallon acre-1 year-1 346 342 357
Ethanol from corn stover (B) gallon acre-1 year-1 - 143 209
Total ethanol (A+B) gallon acre-1 year-1 346 511 565
Electricity exported MWh acre-1 year-1 - 0.94 1.4
Distance driven by an E10-fueled vehicle
103 miles acre-1 year-1 79 110 129
PHA production
PHA from corn grain (A) lb acre -1 year-1 1,484 1,466 1,530
PHA from corn stover (B) lb acre -1 year-1 469 685
Total PHA (A+B) lb acre -1 year-1 1,484 1,935 2,215
Electricity exported MWh acre-1 year-1 - 0.32 0.47
Crude Oil Consumption
-3500
-3000
-2500
-2000
-1500
-1000
-500
0
CC CC50 CwCo70
Cropping system
Cru
de
oil
[lb
ac
re -1
ye
ar-1
]
Ethanol productionsystem
PHA productionsystem
Negative environmental impact represents an environmental credit. Negative environmental impact represents an environmental credit.
Nonrenewable Energy
-70
-60
-50
-40
-30
-20
-10
0
CC CC50 CwCo70
Cropping system
No
nre
new
able
en
erg
y [M
M
Btu
acr
e -1
yea
r-1]
Ethanol productionsystem
PHA productionsystem
Global Warming
-14000
-12000
-10000
-8000
-6000
-4000
-2000
0
2000
4000
CC CC50 CwCo70
Cropping system
Glo
bal
war
min
g [
MM
lb
CO
2 e
q.
acre
-1 y
ear-1
]
Ethanol productionsystem
PHA productionsystem
Eco-efficiency Definition
ratioimpacttalEnvironmen
addedvalueEconomicefficiencyEco
fuel&materialrawofCost
productsofvalueMarketaddedvalueEconomic
credittalEnvironmen
impacttalEnvironmenratioimpacttalEnvironmen
A practice with a greater eco-efficiency would be more sustainable.
Eco-efficiency Analysis • Suppose ethanol and PHA are produced together
from the same unit of arable land.
Crude oil used(0,0)
Nonrenewable energy(0,0)
Global warming(1,0)
X: Fraction of corn grain utilized for producing ethanolY: Fraction of corn stover utilized for producing ethanol
Conclusions• Cropping systems play an important role in the
environmental performance of biobased products.• Utilizing corn stover combined with winter cover crop
production (CwCo70) is the most environmentally favorable cropping system studied here.
• Both ethanol and PHA produced in CwCo70 provide environmental credits in terms of crude oil use, nonrenewable energy and global warming.
• Considering only “sustainable utilization” of biomass (i.e., at maximum eco-efficiency), the fractions of corn grain and corn stover utilized for producing ethanol vary with the impact categories.
• Sustainable, energy-producing approaches are available to produce commodity chemicals & fuels from plant raw materials