Chapter 9 Agriculture
Introduction
• Agriculture results in major environmental
impacts
• 8.5 to 16.5 Pg CO2e/yr (17 to 32% of total
released)
• N2O and enteric methane major contributors
– N2O from fertilizer
– Enteric fermentation from animals
– Growing meat consumption
• N2O emissions growing
9.2 Problems with LCA in Ag
• Widely varying practices
• Lack data sources of individual processes like
seen in a factory
• Differences in soils
– N2O emissions strongly influenced by soil moisture
• Big thing is co-products
– Prime beef, regular, mechanically recovered,
hides, tallow, etc.
9.3 Sugarcane
• Different crops for sugar production
• Generally want the highest return ($/ha)
• Farmers can shift to different crops and
rotations according to prices
• Multiple uses for sugar crops
– Ethanol
– Sugar
– Combustion of fiber
9.3 Sugarcane
• Cradle to grave assessment using Ecoindicator 95
• Functional unit tonne of sugar leaving mill
• Impact categories
–
–
–
–
–
Energy MJ
GHGE kg CO2 eq
Acidification potential (g sulphate equiv) g SO4-2 eq
Eutrophication potential (g phosphate eq) g PO4-3 eq
Fresh water use kL
Initial Findings
• Crop production dominates environmental
burdens – relative to processing
• Two problems
– Variability in crop production systems
– Many of the environmental impacts dominated by
dynamic soil process
• These processes are not very well understood
• Linked it with a soil model on N uses
Variability – Sensitivity Analysis
• Three scenarios allow for an average and 2
extreme results
– Handled by looking at state average farming
system
– Wet tropics scenario (low N, no irrigation, lower
cane yield)
– High yield scenario (high N and irrigation)
Allocation of Inventory Flows
• Co-products handled with economic allocation
and system expansion
• Using economic allocation
– Raw sugar (96%) and molasses (4%)
– 143 kg sugar and 26 kg molasses per tonne cane
– $300/tonne sugar and $70/tonne for molasses
System Expansion
• Difficulty with equivalence when dealing with
substitution of the coproducts
• Molasses replaces 40% barley (supplement
pasture), 20% of wheat (ethanol
fermentation), and 40% nothing (attractant for
cattle)
• Results almost identical for each allocation
approach
Other Allocation Options
• Mass
– Divide allocation by mass of products and coproducts
– 169 kg of products per tonne of cane, sugar is 85%
of mass
• Energy
– Look at energy value of each product and coproduct
– Split allocation by energy output
– Maybe a little difficult with DDGS versus ethanol
Results
• Agricultural activities biggest factor,
processing minor
• Eutrophication potential
– Emissions to air ammonia, N2O and NOx
– Water emissions primarily due to nitrate NO3-,
phosphate, PO4
– Differences due to climate, soil type
– High yield and low yield cases resulted in similar
energy yields
Areas for Data Improvements
• Environmental conditions – climate, soil type,
topography
• Agronomic practices
• Geographic location relative to supporting
infrastructure
Conclusions
• Variability should be considered carefully in ag
crop production, particularly with
environmental impacts
• Traditional LCA models an average process,
agriculture makes this difficult
• Opportunity for quick LCA’s on field scale
• Optimized sugar cane production, not
necessarily best use of land
• Some production practices are difficult to
change – peoples behavior
9.4 Milk Production
• Conventional milk versus ultra high
temperature (UHT) milk
– UHT is heated very quick and hot relative to
conventional milk
– Shelf life of 6 to 9 months
– Stable at room temperature
Results – % of Total Energy
Type
Packaging
Farm
Manufacturing
Retail Transport
Conventional
14
21
14
3
UHT
19
13
18
19
UHT is higher overall in energy. This is due to the longer
transport distances, not as many processing plants.
9.5 Maize to Maize Chips
• Considers soil GHG balances (including N
application) and extends system to include
processing
• Functional unit 400 g packet of corn chips
• Measurement unit were kg CO2 eq/packet
Measurements
• Went to processing facility
• On-Farm measurements of N2O
– Previous 5 years focused on stubble and soil
carbon dynamics
– Looked at following N fertilization
• Zero N and stubble burned
• 329 kg N/ha and stubble burned
• 329 kg N/ha and stubble tilled into soil
Results
• 6% of emissions are pre-farm (mfg inputs)
• 36% on-farm
– N fertilization largest GHGE on-farm
• 58% post-farm
– Electricity for processing biggest factor
– Boxes, transport and oil large factors also
Results Fig 9.3 Horne et al., 2009
Comments on Fig 9.3
• Pre and on-farm operations add $0.4/kg CO2
eq
• Processing has $2/kg CO2 eq
• Pre and on-farm are adding less value per unit
of GHGE
• Makes it harder to invest in abatement
strategies
– Electricity, packaging, and transport maybe a
bigger impact per dollar
9.6 Food Miles
• Local versus global food production
• Idea is that local food with minimal transport
is more environmental friendly
• Two issues
– Food production is about more than
transportation
– Assumes transport is dominate environmental
impact in food production systems
– In general, transport of raw foods relatively small
Food Mile Studies
• Some studies indicated that shipping
tomatoes from Spain instead of greenhouses
in the UK was less impact
• Some areas have advantages in crop
production – New Zealand has year round
grazing
• Shipping fruit from the other hemisphere
might be better than storing for 1 year
Differences in Shipping
• Ambient shipping by sea low impact (although
bunker fuel is very dirty)
• Road trucking in refrigerator trailers is energy
intensive
• Air would be even worse
CSA Impact
• May minimize some of the negative impact
relative to conventional food systems
• Less chemical use, less erosion, less packaging,
fewer food miles, and more crop and
ecosystem diversity
• However, few systematic and complete LCA’s
to justify these statements
9.7.1 Ag Sustainable
• Ag is a major problem (emitter) and potential
savior (biofuels and carbon sinks)
• LCA useful for comparison different options
for a similar product or service
– Wool and nylon (nylon actually better, but not
natural)
9.7.2 Constraints on LCA Applications
to Ag Systems
• Climate change impacts on ag pests, diseases,
crop growth, yields, and water poorly
understood
• Time boundaries – fertilizer or lime available
over multiple years
• Most systems are “established” land use
change “water under the bridge”
LCA and Ag Systems
• Timing and nutrient cycles poorly understood
– Land clearing
– Fuel use on farm
– Fertilizer
– Water
– N2O
– Some studies have indicated that biofuels were
worse than fossil fuels due to N2O
– This focused on GHGE
– Might need more of the eco-indicator type
analysis (chapter 5)
Ketchup Example
• Wide variation in tomato cultivation phase
• Production of ketchup fairly well defined
• Use at home a problem
– Bottle in refrigerator for 1 year had 90% more
embodied energy than a bottle used in 1 month
• Room for “quick” LCA tools for on-farm/field
use
9.7.3 Issues Beyond LCA and Interface
Between Other Decision Tools
• Two apple production systems is a fair use
– Other factors would include rural landscape,
natural heritage, wildlife diversity
– LCA will have trouble with some of these factors
• Economic factors
– Food production is high in the US and EU (20% of
land is set aside)
– Potential food problems in the future
Key Questions
• What is limiting
– Land
– GHGE
– Water
• Will vary by geographic location
• LCA need for evaluating conventional and new
ag systems
– Look for maximum societal benefits
9.8 Conclusions
• Ag LCAs are important
– Land use, water use
– GHGE
– Pollutants
– Fertilizer, N2O
• LCA can help with counterintuitive results
– Food miles
– Natural versus synthetic
Ag Stakeholders
• Need to be effort to educate stakeholders on
the roll of LCA
• Calculators need to be made available for
farmers
• Economic impact and GHGE (corn chip
example)
– Less income derived from farm side than
processing