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: [email protected]Presented at: Carbon Footprint Supply Chain Summit, 24-25 May 2007, London
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Identifying and managing emissions from farms and food chains
Presented at: Carbon Footprint Supply Chain Summit, 24-25 May 2007, London. 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*. - PowerPoint PPT Presentation
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Identifying and managing emissions from farms and food chains
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.