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Climate Change, Compost and Horticulture
Annie Kavanagh
Sustainability Programs
Acknowledgement
This presentation is largely based on the work undertaken by Johannes Biala of The Organic Force, commissioned by the NSW Department of Environment, Climate Change and Water.
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Climate Change, Compost and Horticulture
1. Australian climate change overall
2. Horticulture and Greenhouse gases
3. Carbon story and nitrogen story
4. Bringing you the good news of compost
CSIRO Australian Update
Less rainfall
Climate changes: more hot days average increase 0.9OC, more fires
Sea level rises- 0.5 to 2m by 2100
Sea Level Rises and Coastal Erosion
Coastal erosion hot spots
Eurobodalla Shire Council Batemans Bay
Great Lakes Council Winda Woppa, Jimmys Beach
Wyong Shire Council The Entrance North
Wyong Shire Council Noraville
Wyong Shire Council Norah Head
Gosford City Council Wamberal/Terrigal
Pittwater Council Bilgola
Pittwater Council Mona Vale
Warringah Council Collaroy/Narrabeen
Greater temperature extremes
Plants and climate change
GHG Emissions from Agriculture
Livestock 67%
Ag soils 17%
Manure management 3.9%
Ag N2O is 85.8% national N2O emissions
Australian Agricultural Emissions (gigatonnes)
55,500
3,400
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14,600
1,400 282 Enteric Fermentation
Manure Management
Rice Cultivation
Agricultural Soils
P rescribed Burning ofSavannas
Field Burning ofAgricultural Residues
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Soil C loss
Natural between 40 and 400 t/ha
Av rate of decline ~50%
Caused by accelerated mineralisation, erosion, leaching
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Nitrogen and Climate Change
Denitrification main source of N2O
Emissions affected by:
• Moisture & aeration• Temperature• Soluble C• Fertiliser input• Soil pH
Peat
The Good News
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Potential for Mitigation from Agriculture
Improved practices that increase yields and generate more inputs of C residue
More efficient N use, geared to crop needs
Measures to reduce erosion
Restoration of degraded agricultural land
Global mitigation potential by 2030 ~ 4,500 – 6,000 Mt CO2-e yr – 89% from soil C sequestration.
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Benefits of Diversion
In Australia in 2007, approximately 4.28 Mt CO2 –e saved by diverting organics from landfill, almost the same as was as recovered as landfill gas (4.5 Mt CO2-e). 19
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Diversion Benefits: Greenhouse Gas Savings
2008-2009
In NSW removing organics from landfill saved 277,000 tonnes of CO2-e
That’s more than 5.5 billion black balloons
Soil Carbon Pools
10% fast - short turnover time, with fast decomposition, daily to annual; also known as labile or active pool
40-80% slow - longer turnover time, with slower decomposition, annual to decadal; also known as stable or humus pool
10-50% passive - longer turnover time, decadal to centennial/millennial; also known the recalcitrant or refractory pool.
Using Compost
Around 50% of C contained in raw materials is retained and found in compost, mostly in recalcitrant organic compounds such as humic substances
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Maintaining Soil C
To retain current soil organic levels:
Mature garden organics compost (used on silty loam) 4.8 t DM ha-1 yr-1
Mature biowaste (garden/food organics) compost (used on loamy sand) 3.8 t DM ha-1 yr-1
Pasteurised biowaste (garden/food organics) compost (used on silty clay loam) 2.6 t DM ha-1 yr-1.
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Carbon sequestration
An interim climate mitigation measure:
- 45% of C applied lasts 20 years
- 35% over 50 years
- 10% over 100 years.
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BUT…
Carbon sequestration resulting from compost use can be considered as an interim climate change mitigation measure.
Provides an opportunity for implementing low-cost measures that are immediately available and deliver a wide range of other environmental, agronomic and societal benefits.
Could provide some “breathing space‟, and be used to complement other mitigation measures and low carbon technologies.
Nitrogen use
Continuous compost use will increase nitrogen use efficiency in the initial year after compost application, with a maximum of 40% measured after 21 years of compost use
Mineralisation from mature composts usually occurs faster than from fresh composts,
Combined Effects of Sequestration and Fertiliser Replacement
By adding compost at the rate of 10 t DM ha-1 the following savings can be made
~ 5,224 kg CO2-e in 20 years
~ 3,710 kg CO2-e in 50 years
~ 1,187 kg CO2-e in 100 years
Bonus Savings!
Reduced micronutrients Reduced agricultural lime Reduced gypsum Reduced use of ‘humic’ additives Reduced need for irrigation (pump electricity) Improved tilth – reduced tractor fuel Reduced biocides Reduced soil erosion Increased yields
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But wait – there’s more!(NSW 2008-2009)
$33 million$11.85 m water
$11m phosphate replacement
$3.3m avoided urea
$1.3m reduced acidification
$1m due to reduced salinity
Take Home Messages
Let nature do it! Let nature help by providing cost effective, interim climate change mitigation for the next 20+ years.
Diversion of organics nationally saves almost as much as landfill gas capture does (nearly 4.5 Mt /year).
For 1t DM compost applied per hectare - 118 kgs of CO2-e saved.
It’s not all about C, compost delivers a number of other environmental benefits.
Thank you, and for the earth’s sake, good composting!
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Further Information: Information, resources and case studies
http://www.environment.nsw.gov.au
http://www.recycledorganics.com