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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

Annie Kavanagh

DECCW

annie.kavanagh@environment.nsw.gov.au

Ph: (02) 8837 6016