Transcript Document

Greenhouse Accounting:
The View Beyond Carbon
Chris Mitchell
Chief Executive Officer
CRC for Greenhouse Accounting
All slides © CRC for Greenhouse Accounting 2003
Partners
Industry
(supporting)
•Alcoa of Australia
•Shell
•Stanwell
Corporation
Science programs
Vision
Australia meeting the
greenhouse challenge
supported by world-class
capability in greenhouse
accounting.
Mission
To provide research outputs
for land-based greenhouse
emissions accounting at the
national and project levels.
A Carbon: where is it and how
long do stocks last?
– Above & below ground
carbon (transaction costs)
B The national & global
carbon cycle - ‘Surprises’
– Carbon stock response to
change (risk)
C Model & data integration
– Increase confidence
D Applications & outreach
– Good practice, standards
– Scenarios &
– Quick response
No work on methane or nitrous oxide
Step-wise process for reducing
greenhouse gas emissions
1.
2.
Identify your emissions
Identify the key processes (or process steps) that lead to
emissions
–
3.
Determine the management interventions that may reduce
emissions
–
4.
(estimate the cost of pulling the levers)
Implement changes
–
6.
(work out how to pull the levers)
Evaluate the cost and effectiveness of proposed management
changes
–
5.
(find the levers)
(pull the levers)
Monitor effectiveness
–
(check that the levers work)
1. Agriculture and emissions
• Produces (emissions)
– CO2 (use of fossil fuels, land-use change)
• GWP 1
– CH4 (enteric fermentation, flood irrigation)
• GWP 21
– N2O (soil disturbance, fertiliser, burning)
• GWP 296
• Removes
– CO2 (sinks, agroforestry)
– CH4 (soil sink)
Even the most trivial inspection suggests that identifying
agriculture emissions poses some challenge
Identifying emissions - Nitrous oxide in the
atmosphere
N2O (ppb)
310
ice
atmosphere (Cape Grim)
290
270
250
1000
1200
Source: CSIRO
1400
year
1600
1800
2000
Global nitrous oxide budget
Sources
Tg yr
Range
Natural
9.6
4.6 – 15.9
Anthropogenic
8.1
2.1 – 20.7
17.7
6.7 – 36.6
3.9
3.1 – 4.7
12.3
9 – 16
Total
Imbalance (trend)
Total sinks
(stratospheric)
Implied total source
Source IPCC TAR
16.2
‘Natural’ sources of nitrous oxide
Tg N yr-1
Range
Ocean
Atmosphere
Tropical soils
3.0
0.6
1-5
0.3-1.2
Wet forest
3.0
1.0
2.2-3.7
0.5-2.0
1.0
1.0
9.6
0.1-2.0
0.5-2.0
4.6-15.9
Source
Dry savannas
Temperate soils
Forests
Grasslands
Natural sub-total
Source: IPCC TAR
‘Anthropogenic’ sources of nitrous oxide
Source
Tg N yr-1
Range
Agricultural soils
4.2
0.6 - 14.8
Biomass burning
0.5
0.2 - 1.0
Industrial sources
1.3
0.7 - 1.8
Cattle and feedlots
2.1
0.6 - 3.1
8.1
2.1 - 20.7
Anthropogenic sub-total
Source IPCC TAR
Australia’s emissions by sector (2000)
60
49.3
% of emissions
(all gases)
50
40
30
18.5
20
14.3
10
7.1
5.9
3.1
1.9
Source: National Greenhouse Gas Inventory 2002
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Agriculture emissions trends - Australia
Source: National Greenhouse Gas Inventory 2002
Australian agriculture emissions trends
Ag soils up 23.2% between
1990 and 2000
• 10% less emissions from less
animal waste (< animals)
130 % more N2O emissions
from fertilised crops and pastures
due to increased artificial nitrogen
fertiliser application
• 69.6 % more N2O emissions from
manure application in the field
(poultry)
• an increase of 1.4 % in emissions
of N2O from soil disturbance.
Source: National Greenhouse Gas Inventory 2002
Nitrogen fertiliser sold (Kt)
Trends in N fertiliser sales to pastoral
farmers in Victoria.
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
1980
1982
1984
1986 1988
Year
1990
1992
1994
1996
Data drawn from sale figures of a single fertiliser company in Victoria (Eckard et al. 1997).
2. Identify processes
Nitrification
Nitrosomonas
Autotrophic bacteria
2NH4+ + 3O2
Ammonium
Nitrobacter
2NO2- + O2
2NO2- + 2H2O + 4H+
Nitrite
Aerobic process:
• Occurs in soils
- • Releases energy
2NO3 • Excess of added ammonium
Nitrate can lead to nitrate leaching
• Nitrate is highly soluble and
therefore mobile
Denitrification
5CH2O + 4H+ + 4NO3-
2N2 + 5CO2 +7H2O
Nitrate
Gaseous loss
2NO3Nitrate
2NO2Nitrite
2NO
N2O
Nitric oxide
Nitrous oxide
Facultative anaerobic bacterial
process:
Heterotrophs eg Pseudomonas
• Wet soils
• Where O2 is present
denitrification is turned off
N2
Nitrogen
Conditions favourable to N2O
• low pH (narrow pH range)
•Very low O2 leads to N2
•Temperature
•Available C
•Nitrate & nitrite availability
N2, N2O
Air
System
NH3
N2
Water
Surface applied fertiliser
Aerobic
soil layer
NH4+
Upward
diffusion
NO2-
NO3
Deep
urea
fertiliser
Downward
diffusion
Nitrification
NH4+
Organic N
N2, N2O
Mineralisation
Denitrification
Anaerobic soil layer
Leaching
NO3
Given this how do emissions inventories
‘predict’ N2O?
• Emission of N2O is 1.25% of the N applied
• Global data suggest 1.25±1%
• So for 100 kg of N applied, actual emissions
might be:
– 0.39 kg N2O (115 kg CO2e)
or as much as 3.5 kg N2O (1036 kg CO2e)
 From a manager’s standpoint this is too
coarse – where am I?
Whole-farm GWP Analyses Corroborate Importance of N2O
Midwestern Corn-Soybean-Wheat Rotation (KBS, Michigan):
CO2
System
Δ Soil C
N
Fertilizer
Lime
Fuel
N2O
CH4
Net GWP
GWP (g / m2 CO2-equivalents)
Conv. till
0
27
23
16
52
-4
114
No till
-110
27
34
12
56
-5
14
Forest
0
0
0
0
21
-25
-4
NB: N2O measured; emission factor = 0.56%
Source: Robertson et al. Science 289:1922 (2000)
The Australian data-base
Net flux of N gases
Nitrous oxide emissions are difficult to predict
Water-filled pore space
…meanwhile back at the (cotton) farm
N2O loss
NH3 + N2 loss
N into plant tissue
(the bit generally measured)
N ‘immobilised’
in soil
NH3 loss
N transport in water
(sometimes deliberate)
Nitrate leaching
CH4
Whereas for pasture/livestock
Soil nitrate
Denitrification
N2
Nitrification
Fertiliser N
N2O
Soil ammonium
Legume
Utilisation
Leaching etc
3. Work out how to pull the levers
Environmental
‘Physical’
• Water
• Temperature
• C availability
– soil type
– rainfall
Biological
• Microbial flora
• Acclimation
Management (levers)
‘Practices’
• Amount of N applied
• Form applied
• Timing of application
‘Codes’
• BMPs
• EMS
• Accounting systems
• Policies
4. Indicative ($) Value of Benefits
• Dairy, grains and cotton
– 40% of the value of farm output
– almost $12b of exports in 2000-01
• Potential annual abatement of greenhouse gases
– 1.2 Mt per annum, worth conservatively $21.7m
• recent modelling suggests four times this is possible
• Savings in farm costs through using less fertiliser
worth $116m annually
• Systems management
– hard to quantify but water savings alone could be
worth several hundred million dollars annually
– water quality benefits
What’s needed
•
Real data on (N2O and CH4) emissions linked to environmental
drivers
– Sort out methods, develop protocols
– Enterprise relevant, prioritised
• Grains
• Cotton
• Dairy
•
•
Develop models to generalise
Best management practice
– Whole of farm greenhouse balances
• Extension
– Partnership
– International
Putting it all together
Field
measurements:
wheat, grazing
Data-sets for:
calibration/testing
Scaling-up,
Knowledge into
systems:
(Models)
Define important
systems
knowledge gaps
Best Management
Practice
Users
International
collaboration
In summary…& other observations
Greenhouse mitigation in agriculture is difficult because of knowledge
gaps
–
These knowledge gaps can be plugged
Agricultural systems are among the most complex for mitigation
Substantial gains are to be captured:
–
Greenhouse
–
Economic
–
Other environmental
•
•
•
N leaching: water quality
water management
‘tighter’ systems
And the systems that we are dealing with are already responding to
climate change, but that’s a whole other story
Agriculture
• Enteric fermentation
– methane
– by animal
• Manure management
– methane
• Rice cultivation
– methane from anaerobic soil processes
• Agricultural soils
– CH4 & N2O
• Prescribed burning of savanna
– Non-CO2 greenhouse gases (excludes
CO2)
• Field burning of agricultural residues
• Other