Good afternoon. The NSW Government is committed to establishing a sound scientific basis for understanding climate change and developing adaptation responses. The NSW Government in its State Plan set a target for reducing greenhouse gas emissions by 60% by the year 2050. This document addresses a number of key priority areas for climate change actions including waste reduction and climate change adaptation. I will firstly give the briefest of updates on climate change figures in Australia, and I will then look at some of the relationships that greenhouse gases have to horticulture and I will then explore the carbon and nitrogen cycles in more detail. Finally, I am here to do a sell job – to explain to you why compost has a great role for you and your business in helping society tackle climate change
A report made public by the European Environment Commission in March, 2009 underlines the crucial role that soils can play in mitigating climate change. “ Soils contain around twice the amount of carbon in the atmosphere and three times the amount to be found in vegetation. Soils are an enormous carbon reservoir”, containing around 1600 billion tonnes, and “poor management can have serious consequences ”. The report underlines the need to sequester carbon in soils – “ the technique is cost competitive and immediately available, requires no new or unproven technologies, and has a mitigation potential comparable to that of any other sector of the economy .”
A brief Australian update, published by the CSIRO at the end of last year: * Rainfall Since 1950, most of eastern and south-western Australia has experienced substantial rainfall declines. Across New South Wales and Queensland these rainfall trends partly reflect a very wet period around the 1950s, though recent years have been unusually dry. In contrast, north-west Australia has become wetter over this period, mostly during summer. From 1950 to 2005, extreme daily rainfall intensity and frequency has increased in north-western and central Australia and over the western tablelands of New South Wales, but decreased in the south-east and south-west and along the central east coast Temperature * Australian average temperatures have increased 0.9°C since 1950, with significant regional variations. The frequency of hot days and nights has increased and the frequency of cold days and nights has declined. Oceans Global sea levels rose by about 17 cm during the 20th century, and by around 10 cm from 1920-2000 at the Australian coastal sites monitored. Substantial warming has also occurred in the three oceans surrounding Australia, particularly off the south-east coast and in the Indian Ocean. reef-building corals are under increasing physiological stress from a changing climate and increasing uptake of carbon dioxide by the oceans. Skeletal records of corals in the Great Barrier Reef show that calcification has declined by 14.2% since 1990. The data suggest that such a severe and sudden decline in calcification is unprecedented in at least the past 400 years.
Following a map of where temperature increases have occurred since 1970 (from the BOM)
This graph shows the mean temperature anomaly since 1900. An anomaly is a deviation from the normal or typical condition. The World Meteorological Organization has found that 2000-2009 was the world’s warmest decade on record, warmer than the 1990s which in turn was warmer than the 1980s. In Australia, the Bureau of Meteorology has found each decade since the 1940s has been warmer than the preceding decade. The Earth has warmed by around 0.74 degrees Celsius from 1906-2005. This is a statistically significant climatic change.
In the twentieth century, the global average sea level rose by 17 cm and sea levels are projected to continue to rise. There is strong national and international evidence supporting a projected rise of up to 40 cm by 2050, and 90 cm by 2100, for the NSW coastline. Coastal land has been subject to natural coastal hazards for thousands of years, including coastal erosion and coastal flooding. Projected sea level rises will increase these hazards, and NSW needs to plan now for these long-term impacts to minimise social and economic disruption.
Greater temperature extremes will make our environment more prone to droughts, floods and fires. We will not be able to say, for example, that the floods this year were caused by climate change, but we do know that rising temperatures over a longer period will have a significant effect – and it is at the margins where these effects will be most felt.. Dr Kate Hammill from the Fire ecology Unit
Emissions of greenhouse gases are produced a result of a number of natural and human processes. These include the decay or burning of biomass, ‘burps of ruminant livestock, the addition of nitrogen fertiliser and animal manure, crop residues returned to the soil, nitrogen fixation, nitrogen leaching and runoff, atmospheric deposition, and the anaerobic decomposition of organic matter during flood irrigation. The principal greenhouse gases accounted for from horticulture and agriculture are methane (CH4) and nitrous oxide (N2O). The main agricultural sources of CH4 are the digestion of feed by livestock, manure management and the burning of pastoral grassland and woodland. The main agricultural source of N2O is soils, primarily as a result of the use of nitrogen-based fertilisers on crops and pastures. Manure management and burning are also sources of N2O. Greenhouse gas emissions represent a loss of valuable resources from farming systems. There is a wide range of actions that land managers can take in order to enhance the efficiency with which these resources are used, thereby reducing their greenhouse impacts and improving productivity at the same time.
The Australian National Greenhouse Gas Inventory, 2007, has reported the GHG emissions from agriculture. Of the total emissions of approximately 576,000 Gt emitted in Australia, approximately 14 per cent of Australian greenhouse emissions come from agriculture and 67 per cent of that is methane produced by livestock. Ag soils emit approx 17% and manure management accounts for some 3.9%. Of all the N 2 O emissions in Australia, nearly 86% comes from agricultural sources.
Looking at those numbers in gigatonnes, we can again see that agricultural emissions are dominated by enteric emissions, colloquially referred to as the ‘farts and burps’ of livestock, particularly cows. The size of the beef herd is the main driver of agricultural emissions. Livestock numbers are largely driven by growth in export and domestic demand, the ability of the land to support these livestock numbers in drought conditions and a general shift in both domestic and international consumer preferences towards meat products. It is worth noting the significant contribution made by agricultural soils and noting that manure ‘management’, does not include composting.
As we have seen, emissions from agricultural soils are the third highest form of emission. Soil organic carbon losses in agricultural systems are caused by accelerated mineralisation, erosion and leaching, and are enhanced by regular ploughing, planting, and harvesting. There is a world-wide decline in soil organic carbon levels which has contributed to elevated carbon dioxide emissions. In Australia, there has been a considerable soil C loss since the clearing of native pastures and forests for agriculture. This loss ranges from 40 to 400 tonnes per hectare. The average rate of decline is 50%.
Although nitrogen emissions are comparatively small, they are potent, at around 320 times the potency of Carbon dioxide. Moisture and aeration Maximum N2O emissions usually occur when soil water content provides for an abundance of aerobic and anaerobic sites. Temperature Nitrification and denitrification occur primarily with temperatures between 25 and 35 degrees Celsius, with more N 2 O emissions occurring as the temperature gets closer to 35 o . Soil pH At pH levels above 8.0 and below 5.5 to 6.0, N2O emissions can be several times higher than in neutral soil. Easily degradable organic compounds are the source of energy for denitrifying organisms.
The contribution of the worldwide drying out of peat stores through either harvesting or the conversion of peat lands to agriculture, adds substantially to agricultural emissions, and should not be ignored. Peat extraction has largely stopped in NSW, however the peat bogs in the Alpine, Blue Mountains and Southern Highlands areas are at risk because of fires, coal mining, erosion and exotic weed invasion. The risk of fires is particularly potent and in this, we can see the notion of ‘feedback’ mechanisms being played out – the hotter and drier the climate, the more the peat lands break down and emit methane thus adding to the GHG’s which produce the hotter and drier conditions. And so on – as a feedback loop.
Now that we have heard about the negative contributions of agriculture to GHG emissions, we need to look at how ag practices can mitigate climate change effects.
There is a potential for agriculture to mitigate climate change, and this potential is substantial. Potential for mitigation is generated when changes include: 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 CO 2 -e yr – 89% from soil C sequestration.
Before looking at agricultural practices in more detail, we must look at the very good news story that lies in the diversion of organics from landfill (such as garden organics, food organics, wood, timber, biosolids and manures) – that is before it is ever applied in agriculture: The diversion of organics which would have otherwise been landfilled in Australia in 2007 was 4.28 Mt CO2 –e, almost as much as was saved by landfill gas capture – (at 4.5 MtCO2e- in 2007). This figure is not in the National Carbon Accounts, and DECCW is working towards getting the figures sufficiently robust to be included in the National Accounts. Johannes Biala’s work, the literature review commissioned by DECCW has estimated that if just 50% of organic material currently going to landfill nationally was composted approximately 10MtCO2 -e could be saved per year.
In NSW in 2008-2009, approximately 277,000 tonnes of CO2 equivalent was saved by diverting organics from landfill. For those of you familiar with NSW and Victorian Government’s Black Balloon campaign - that’s more than 5.54 billion black balloons.
For convenience, the organic soil carbon pools are often grouped into three pools according to the speed of breakdown and replacement: fast - this pool has a short turnover time, with fast decomposition (e.g. daily to annual); also referred to as the labile or active pool slow - this pool has a longer turnover time, with slower decomposition (e.g. annual to decadal); also referred to as the stable or humus pool passive - this pool has a much longer turnover time (e.g. decadal to centennial/millennial); also referred to as the recalcitrant or refractory pool. The proportion of total soil carbon in each pool can vary widely, but is assumed to be in the range of 10% for the fast pool,40% to 80% for the slow pool, and 10% to 50% for the passive pool.
Compost is a complex mixture of inorganic and organic components, ranging from labile to resistant in terms of degradability, as well as dissolved organic carbon, which may be degraded or leached. As with other organic soil amendments, the rate and extent of mineralisation of compost products after application to soil depends on the quantity, type, maturity and particle size distribution of the applied product, as well as on soil properties, environmental conditions, and agricultural management practices. The longer the organic materials are composted, the smaller the portion of organic matter degrades after soil application. The question that everyone here is interested in understanding the answer to is “Just how much does compost contribute to soil C sequestration?”
Firstly, we should look at how much compost we need to add just to maintain soil C. Maintenance of soil c levels is critical for a range of agricultural and environmental reasons. Over the many trials that have been conducted, it has been estimated that just to maintain the levels of carbon in soils, the following amounts of compost have to be added annually. o Mature garden organics compost (used on silty loam) 4.8 t DM ha-1 yr-1 o Mature biowaste compost (used on loamy sand) 3.8 t DM ha-1 yr-1 o Pasteurised biowaste compost (used on silty clay loam) 2.6 t DM ha-1 yr-1.
The application of compost to arable soils can increase soil organic carbon levels; this has been demonstrated in Europe (UK and Germany), North America and Australia. It is important to consider the sequestration of compost-derived carbon over both the long-term (100 years) and the medium term (20 to 50 years). Carbon sequestration resulting from compost use is an important interim climate change mitigation measure, because it provides opportunities for implementing low-cost measures that are immediately available and deliver a wide range of other environmental, agronomic and societal benefits. Such measures could provide some “breathing space‟, which allows for the development, testing and implementation of other mitigation measures and low carbon technologies. Based on the various studies that Johannes Biala has reviewed, the figures on the screen were calculated, ie 45% of carbon applied with compost is retained over a 20-year period, 35% over a 50-year period, and 10% over a 100-year period.
Carbon sequestration resulting from compost use can be considered as an interim climate change mitigation measure. Such measures are important because they provide opportunities for implementing low-cost measures that are immediately available and deliver a wide range of other environmental, agronomic and societal benefits. Such measures could provide some “breathing space‟, and be used to complement other mitigation measures and low carbon technologies.
Compost’s contribution to climate change mitigation does not stop with soil c sequestration or diversion benefits. Replacing, or partially replacing, nitrogenous fertilisers also forms part of compost’s contribution. Because only a small proportion of the total nitrogen applied with compost is mineralised and used by plants, continuous compost use increases soil nitrogen levels substantially, providing significantly higher soil nitrogen supply potential. In trials, nitrogen use efficiency ranged between an average of 2.6% and 10.7% during the first year after compost application; subsequent (three or more years after compost application) nitrogen availability depends largely on site and production-specific conditions but is generally in the range of 2–3% of added compost nitrogen. Continuous compost use will increase nitrogen use efficiency in the initial year after compost application, with a maximum of 40% efficiency measured after 21 years of compost use. Mineralisation from mature composts usually occurs faster than from fresh composts. Fresh compost as well as those with high C/N ratio usually incur temporary nitrogen drawdown.
By combining the sequestration benefits and the benefits of replacing mineral fertiliser we can arrive at the following figures per 10 tonne of Dry Matter compost applied per hectare.
Apart from sequestering carbon, substituting the use of mineral fertiliser, and possibly reducing nitrous oxide emissions, the use of compost offers additional opportunities for reducing GHG emissions directly and indirectly. These include: reducing/avoiding the use of micronutrients reducing/avoiding the use of agricultural lime reducing/avoiding the use of gypsum avoiding the use of humic substances on their own as soil improvement treatment reducing need for irrigation and the associated use of fuel/electricity reducing the use of tractor fuel due to improved tilth reducing erosion and loss of soil and nutrients reducing the use of biocides increasing yields, and hence improving the efficiency per unit of input.
Looking at the application benefits, we know that there are a range of other good news stories to be told. Water is one of the most important (and saleable) of these benefits. In NSW in 2008-2009, we estimated the following valuing of environmental benefits from applying 500,000 tonnes of material (conservative figure, seeing that 1.9 million cubic metres of material were sold). Some of our studies have shown water savings of between 30 and 50% this is not only saving water, it can mean the difference between a crop and no crop at all. It will certainly save money. Using the environmental benefit costings from the DECCW 2004 Triple Bottom Assessment of Garden Organics (Nolan ITU) report, we can estimate environmental savings (for 2008-2009), these include: $11.85 million savings due to water retention $11 million due to phosphate replacement $3.3 million in avoided urea $1.3 million due to reduced acidification $1.3 soil carbon sequestration $1 million due to reduced salinity This is conservative – based on the application of only 500,000 tonnes.
Please advise if you’d like to be notified when the report has been published.
Acknowledgement <ul><li>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. </li></ul>
Climate Change, Compost and Horticulture <ul><li>Australian climate change overall </li></ul><ul><li>Horticulture and Greenhouse gases </li></ul><ul><li>Carbon story and nitrogen story </li></ul><ul><li>Bringing you the good news of compost </li></ul>
CSIRO Australian Update <ul><li>Less rainfall </li></ul><ul><li>Climate changes: more hot days average increase 0.9 O C, more fires </li></ul><ul><li>Sea level rises- 0.5 to 2m by 2100 </li></ul>
Coastal erosion hot spots Collaroy/Narrabeen Warringah Council Mona Vale Pittwater Council Bilgola Pittwater Council Wamberal/Terrigal Gosford City Council Norah Head Wyong Shire Council Noraville Wyong Shire Council The Entrance North Wyong Shire Council Winda Woppa, Jimmys Beach Great Lakes Council Batemans Bay Eurobodalla Shire Council
GHG Emissions from Agriculture <ul><li>Livestock 67% </li></ul><ul><li>Ag soils 17% </li></ul><ul><li>Manure management 3.9% </li></ul><ul><li>Ag N 2 O is 85.8% national N 2 O emissions </li></ul>
Soil C loss <ul><li>Natural between 40 and 400 t/ha </li></ul><ul><li>Av rate of decline ~50% </li></ul><ul><li>Caused by accelerated mineralisation, erosion, leaching </li></ul>
Nitrogen and Climate Change <ul><li>Denitrification main source of N 2 O </li></ul><ul><li>Emissions affected by: </li></ul><ul><li>Moisture & aeration </li></ul><ul><li>Temperature </li></ul><ul><li>Soluble C </li></ul><ul><li>Fertiliser input </li></ul><ul><li>Soil pH </li></ul>
Potential for Mitigation from Agriculture <ul><li>Improved practices that increase yields and generate more inputs of C residue </li></ul><ul><li>More efficient N use, geared to crop needs </li></ul><ul><li>Measures to reduce erosion </li></ul><ul><li>Restoration of degraded agricultural land </li></ul><ul><li>Global mitigation potential by 2030 ~ 4,500 – 6,000 Mt CO 2 -e yr – 89% from soil C sequestration. </li></ul>
Benefits of Diversion <ul><li>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). </li></ul>
Diversion Benefits: Greenhouse Gas Savings <ul><li>2008-2009 </li></ul><ul><li>In NSW removing organics from landfill saved 277,000 tonnes of CO2-e </li></ul><ul><li>That’s more than 5.5 billion black balloons </li></ul>
Soil Carbon Pools <ul><li>10% fast - short turnover time, with fast decomposition, daily to annual; also known as labile or active pool </li></ul><ul><li>40-80% slow - longer turnover time, with slower decomposition, annual to decadal; also known as stable or humus pool </li></ul><ul><li>10-50% passive - longer turnover time, decadal to centennial/millennial; also known the recalcitrant or refractory pool. </li></ul>
Using Compost <ul><li>Around 50% of C contained in raw materials is retained and found in compost, mostly in recalcitrant organic compounds such as humic substances </li></ul>
Maintaining Soil C <ul><li>To retain current soil organic levels: </li></ul><ul><li>Mature garden organics compost (used on silty loam) 4.8 t DM ha-1 yr-1 </li></ul><ul><li>Mature biowaste (garden/food organics) compost (used on loamy sand) 3.8 t DM ha-1 yr-1 </li></ul><ul><li>Pasteurised biowaste (garden/food organics) compost (used on silty clay loam) 2.6 t DM ha-1 yr-1. </li></ul>
Carbon sequestration <ul><li>An interim climate mitigation measure: </li></ul><ul><ul><li>45% of C applied lasts 20 years </li></ul></ul><ul><ul><li>35% over 50 years </li></ul></ul><ul><ul><li>10% over 100 years. </li></ul></ul>
BUT… <ul><li>Carbon sequestration resulting from compost use can be considered as an interim climate change mitigation measure. </li></ul><ul><li>Provides an opportunity for implementing low-cost measures that are immediately available and deliver a wide range of other environmental, agronomic and societal benefits. </li></ul><ul><li>Could provide some “breathing space‟, and be used to complement other mitigation measures and low carbon technologies. </li></ul>
Nitrogen use <ul><li>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 </li></ul><ul><li>Mineralisation from mature composts usually occurs faster than from fresh composts, </li></ul>
Combined Effects of Sequestration and Fertiliser Replacement <ul><li>By adding compost at the rate of 10 t DM ha-1 the following savings can be made </li></ul><ul><li>~ 5,224 kg CO 2 -e in 20 years </li></ul><ul><li>~ 3,710 kg CO 2 -e in 50 years </li></ul><ul><li>~ 1,187 kg CO 2 -e in 100 years </li></ul>
Bonus Savings! <ul><li>Reduced micronutrients </li></ul><ul><li>Reduced agricultural lime </li></ul><ul><li>Reduced gypsum </li></ul><ul><li>Reduced use of ‘humic’ additives </li></ul><ul><li>Reduced need for irrigation (pump electricity) </li></ul><ul><li>Improved tilth – reduced tractor fuel </li></ul><ul><li>Reduced biocides </li></ul><ul><li>Reduced soil erosion </li></ul><ul><li>Increased yields </li></ul>
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 <ul><li>Let nature do it! Let nature help by providing cost effective, interim climate change mitigation for the next 20+ years. </li></ul><ul><li>Diversion of organics nationally saves almost as much as landfill gas capture does (nearly 4.5 Mt /year). </li></ul><ul><li>For 1t DM compost applied per hectare - 118 kgs of CO 2 -e saved. </li></ul><ul><li>It’s not all about C, compost delivers a number of other environmental benefits. </li></ul>
Thank you, and for the earth’s sake, good composting!
Further Information: Information, resources and case studies http:// www.environment.nsw.gov.au http:// www.recycledorganics.com