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 co-

products– 169 kg of products per tonne of cane, sugar is 85%

of mass• Energy– Look at energy value of each product and co-

product– 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 EnergyType 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