Identifying and managing emissions from farms and food chains

Gareth Edwards-Jones

Georgia Koerber Liz York

Llorenç Milà i Canals*

University of Wales, Bangor

University of Surrey*Contact: g.ejones@bangor.ac.uk

Presented at:

Carbon Footprint Supply Chain Summit, 24-25 May 2007, London

Key messages

• Lack of knowledge

• Complexity

• We can assume ‘too much’

Based on on-going research ‘Comparative assessment of the advantages and disadvantages of growing fruit and vegetables in the UK and

overseas’ funded by the UK Research Councils’ Rural Economy and Land Use programme (RELU).

Outline

• Definitions

• Different ways of estimating ‘carbon footprint’

• Commercial relevance of these different measurement methods

• Overview of agricultural emissions and what it means

• What does this mean for business and the planet?

Carbon is not the only cause of climate change

– Nitrous oxide (N2O) : 1kg = 296 kg CO2-eq/kg

– Methane (CH4): 1 kg = 23 kg CO2-eq/kg

– Others include CFCs, halons, methyl bromide, sulphur hexafluoride, halogenated HC, mono/di/trichloromethane…)

So to get the whole picture we really need to talk about GLOBAL WARMING POTENTIAL (GWP)

Method 1 – food miles

Emissions from food miles

Transport type kg CO2 (direct)/t*km kg CO2-eq (GWP)/t*km

Passenger car 0.191

kg /passenger km

0.203

kg /passenger km

Van <3.5t 1.076 1.118

Truck, 16t 0.304 0.316

Truck, 32t 0.153 0.157

Plane, freight# 1.093# 1.142

Train, freight 0.037 0.038

Transoceanic freight 0.010 0.011

Transoceanic tanker 0.005 0.005

Assessment

Measure Comprehension by public

Measurement and

calculation

Planet saving ability

Food miles High Easy Poor

Method 2: Life Cycle Assessment (LCA)

The food system

Farm

Transport

Storage & processing

Retail

INPUTS OUTPUTS

MachineryPesticidesFertiliserElectricityFuel

FoodWastesPollution

MachineryFuel

MachineryElectricity

Pollution

PollutionWastes

ElectricityPackaging

WastesPollution

The LCA for inputs to potatoes in UK

Global Warming Potential (GWP 100 years) kg CO2-Equiv./tonne potatoes at the farm gate

• Fertiliser 42

• Pesticide 2.5

• Machinery 5.1

• Mechanisation 66.4

Normalised impact assessment for watercress sourced from the UK (organic and conventional), the USA (organic and conventional) and Portugal (conventional) (Sim et al. 2006)

Lettuce data – on measurement v standard

GWP CO2-equiv (100yrs) per kg of lettuce at the farm gate for 2 UK farms supplying lettuce between January and

April.

• Farm 1 – 3.72 kg CO2-equiv

• Farm 2 – 1.18 kg CO2-equiv

Source: Mila i Canals et al .(2007a)

Primary energy use per kg of apples from European and Southern Hemisphere suppliers for the different seasons

(Mila i Canals et al .2007b)

Energy consumption in the life cycle of 1

kg of potatoes

0

2

4

6

8

10

12

Energy (gross calorific value,MJ)

MJ/

kg

of

coo

ked

po

tato

es

Potato storage andpackaging

UK cropping potato,cradle to farm gate

Transport and retail

Home processing

Assessment

Measure Comprehension by public

Measurement and

calculation

Planet saving ability

Food miles High Easy Poor

Standard LCA Medium - high Medium Medium

Soil – the missing elephant

Removal in crops and animal products

Biological fixation (N2)

Nitrification

Immobilisation

Mineralisation

Gaseous loss (NH3, N2O, N2)

Microbial Biomass

Soil Organic Matter (SOM)

NO3-

Nitrate

NH4+

Ammonium

Root uptake (NH4

+, NO3-)

Leaching (NO3

-)

Exchangeable NH4

+

Rainfall (NH4

+, NO3-) Fertilisers, manures,

plant residues

Rothamsted quote crop residues with nitrogen content < 1.2-1.3% (C/N=30) causes Immobilisation of soil or fertiliser N. > 1.8-2% (C/N=20) results in Mineralisation

Most uptake as NO3-

within plant NO3-

reduced to NH4+

Nitrification involves conversion of ammonium-N 1st to nitrite-N and then to nitrate-N mediated by specific soil bacteria:NH4

+ NO2- NO3

-

When annual crop residues are returned to the soil, breakdown is normally 70% complete within 12 months

Heterotrophic micro-organisms transform SOM 1st to amino-N and then to ammonium-N

Clovers and Lucerne leave 150-200 kgN/ha, Peas and beans leave 20-50 kgN/ha nitrogen.

Nitrate-enriched groundwater leads to eutrophication.

NH3 clings to water droplets, eventually resulting in acid rain. Fossil fuel combustion including the Haber-Bosch process has caused 6-7 fold increase in NOx flux to the atmosphere

Nitric acid is formed from water droplets and N2O, process of wet deposition. Dry deposition is oxides sticking to soil and plants, accounting for 20-60% of total acid deposition.

or put more simply……..

Humus

or

organic matter

or

soil organic carbon

MICROBIAL COMMUNITY

Plant material

Fertiliser(organic and inorganic)

Nitrous oxideMethane

Carbon dioxide

Comparative losses in Carbon

• The UK’s current industrial CO2 emission is 0.04 G tonnes C per year (and falling) (Bellamy et al 2005).

• One study suggests that since 1978 UK soil has lost 0.013 G tonnes C per year based on change in soil organic carbon (Bellamy et al. 2005).

• Therefore, UK soils are losing carbon from soil at one third the rate of industrial emissions.

• The fuel used to import food and drink to the UK accounts for 0.001 G tonnes C per year (Pearce 2006).

If these figures are correct UK soils are losing carbon at 13 times the rate of emissions from food imports.

1 Gt = 1015g

Nitrous oxide

Between 66% and 70% of N2O emissions are derived from soil (IPCC 2000; Bouwman 1990).

English emissions in 2002:

• synthetic fertiliser application (27%)• leaching of fertiliser nitrogen to ground and surface water (26%)• wastes from grazing animals (13%)• ploughing in crop residues (13%)• manure used as fertiliser (8%)• atmospheric deposition of ammonia (NH3) and oxides of nitrogen (NOx)

(6%)• cultivation of legumes (2%)• cultivation of histosols (i.e. high organic content soils) (0.7%)• biological fixation in improved grass (0.5%)

(Defra 2004)

Soil Emissions of Nitrous Oxide and Methane

• Applying a typical emission factor of 2.2%, leads to an emission of 6.6 to 13.2 kg N2O-N ha-1 (Tzilivakis et al., 2005).

• Equivalent to CO2 emissions in the range of 3 to 6 CO2-Equiv./tonne/ha

The soil organic content to typical agricultural land is

440 CO2-Equiv./tonne/ha

Relatively small emissions of N2O can exert a strong influence on the total GWP of an ecosystem.

Methane

• UK agriculture emits 873,000 t methane per year.

• Land fill emits 928,000 t – a lot of this from food waste

• Cattle responsible for 70% of the agricultural emissions.

• 87% of total emissions is due to enteric fermentation.

• Agricultural soils with plenty of oxygen are actually methane sinks.

(Defra 2004)

The public and The Green Room

• But to say that soil itself contributes to greenhouse gas should make people either alarmed or sceptical about this report's implications..

Jeremy Mason

 

• This article is short-sighted, inaccurate, and misleading. To insinuate that the green house gasses from the soil are responsible for environmental degradation is ridiculous.

D., USA

 

• The bit about the gases produced by different kinds of soil seems to me unnecessary for the issue at hand, unless the author is claiming that significant pollution results from our choice of soil. THAT would be news.

Dustin, Philadelphia

Variation with emissions

Gaseous emissions from soils differ with:

– Temperature

– Soil type

– Soil moisture

– Crop?

– Crop management?

Spanish Soil with Rising and Falling Limbs Overlying

0

1

1

2

2

3

3

4

5 10 15 20 25 30

Temp (°C)

Soil

Res

pira

tion

(μg

CO

2 g

-1 h

-1)

Temperature vs Soil Rise Temperature vs Soil Fall

Effect of temperature on CO2 emissions

Source: York unpublished

Regional distribution of average emissions of CO2-equivalents from soils, normalised by the area of agricultural land in the NUTS 2

regions (Freibauer 2003).

Average emissions of CO2-equivalents per hectare from agricultural ecosystems in Europe (Freibauer 2003).

9:00 12:00 15:00 18:00

0

5

10

15

20

25

0

100

200

300

May 2005

9:00 12:00 15:00 18:00

0

5

10

15

20

25

0

100

200

300

June 2005

9:00 12:00 15:00 18:00

0

5

10

15

20

25

0

100

200

300

July 2005

Soil Temperature 0C

Time of Day

9:00 12:00 15:00 18:00

0

5

10

15

20

25

0

100

200

300

August 2005S

oil

CO

2 E

fflu

x +

/- 2

SE

M

(µm

ol.m

-2.s

-1)

So

il CO

2 Efflu

x +/- 2

SE

M (to

n.h

a-1.yr

-1)

Assessment

Measure Comprehension by public

Measurement and

calculation

Planet saving ability

Food miles High Easy Poor

Standard LCA Medium - high Medium Medium

LCA with soil emissions

Low Hard Better

Summary so far

• So the missing element from many carbon footprints so far relates to the absence of measured emissions data – which clearly vary a lot over time and space.

• But it’s even worse than that…..

Carbon Budget Studies

Description of Study NEP (t C ha-1 yr-1)

Winter wheat (Triticum aestivum L.), Thuringia, Germany (Anthoni et al., 2004).

1.85-2.45

(Eddy Covariance)

2.52 ± 0.34 (Calculated)

Mixed coniferous- broadleaved foresta, meadow steppeb and typical steppec, North East China Transect (Zhou et al., 2002).

5.03a, 2.27b and 1.75c

No till, bare field with only wheat straw (Triticum aestivum L.) additions, Ohio USA (Duiker and Lal, 2000)

Annual straw addition rate0 2 4 8 163.84 5.64 4.51 5.34 6.63

Carbon Budget Studies

Description of Study NEP (T C ha-1 yr-1)

Corn/Soybean Conventionald (full width tillage) versus Alternativee (reduced tillage, spring oats before barley) (Baker and Griffis, 2005)

3.76d, 3.50e

Restored prairie: Maize, no-tillage, unfertilised: Maize chisel-plowed, unfertilised:Maize no-tillage, fertilised:Maize chisel-plowed, fertilised:(Brye et al., 2002)

-1.70.6-0.31.12.5

Onion (Allium cepa L.) Fertilised:Mikasa, Japan. Unfertilised:(Hu et al. 2004) Fertilised, bare: Unfertilised, bare:

1999 20000.02 and 0.27

-0.28 and -0.70 -1.9 and -2.1 -2.1 and -2.2

Assessment

Measure Comprehension by public

Measurement and

calculation

Planet saving ability

Food miles High Easy Poor

Standard LCA Medium - high Medium Medium

LCA with soil emissions

Low Hard Better

LCA with full carbon budget

Low V. hard The best

Key messages for those devising carbon footprints for agriculture

• Need a Systems approach.

• There is considerable diversity in food production systems and the environments where they occur.

• Collection of system / site specific data is important.

• Standard databases will improve with time – but have deficiencies at the moment.

GHG Account for UK agriculture, land use and forestry (2004)

Category CO2 equivalent (millions of tonnes)

%

Enteric fermentation 16.9 34.7

Manure management 3.4 7.0

Agricultural soils 26.4 54.2

Agriculture total 46.8 96

Land use change & Forestry (net)

1.9 4

Netcen (2004)

Means of achieving carbon neutral food:in the food chain

• Renewable energy for manufacturing inputs

• Energy efficient food transport

• Energy efficient food storage

• Energy efficient kitchens

• Reduce waste

• Reduce land used in food production and have more ‘wild land’ to act as a carbon sink.

• Close nutrient cycling loop by putting food waste (and STW) back to land

• Fewer people?

Means of achieving carbon neutral food:on the farm

• Reduce methane production from ruminants:

• Reduce emissions of N2O:

• Reduce emissions of CO2 :

• Feeding strategies• GM• Fewer animals

• Reduce cultivations• Reduce cultivated area

• Reduce fertiliser use• Better timing of fertiliser• GM N-fixing crops

Will carbon accounting save the planet?

NO

But it’s more likely to help if….

• The public understand the issues and care enough to use the market to bring about change.

• Business and Government use the correct science.

• Scientists communicate clearly and understand the needs of business.