Using compost and other biological additives to increase soil carbon and drawdown CO2

Research has shown that more carbon can be sequestered through increasing microbial action in healthy soils by application of compost (coupled with other land use changes) than any other methodology, including tree planting.

Soil carbon drawdown is the quickest, cheapest (and most intelligent!) way to halt and reverse climate change, with some amazing co-benefits such as healthier food, increased yields and drought resilience.

Increasing organic matter in soils (and therefore carbon) can be partly achieved by capturing the nutrients in organic waste from our cities through composting (from backyard worm farms to industrial wind row composting), and returning this microbe and nutrient rich material back to the soil. It can happen really quickly with enough resources and political will, and is a much more cost effective way to treat organics and lower emissions than burning the same organic waste in waste to energy systems

We’ve summarised what is of course a very complex topic below with some learned quotes, including excerpts from pioneering work by Dr Christine Jones, who I have heard talk about this topic.

“A soil carbon improvement of only 0.5% in the top 30 centimetres of 2% of Australia’s estimated 445 million hectares of agricultural land would safely and permanently sequester the entire nation’s annual emissions of carbon dioxide. Sequestering atmospheric carbon in soil as humified organic carbon would also restore natural fertility, increase water-use efficiency, markedly improve farm productivity, provide resilience to climatic variation and inject much-needed cash into struggling rural economies.

The ‘soil solution’ to removing excess carbon dioxide (CO2) from the earth’s atmosphere is being overlooked because current mathematical models for soil carbon sequestration fail to include the primary pathway for natural soil building. The process whereby gaseous CO2 is converted to soil humus has been occurring for millions of years. Indeed, it is the only mechanism by which topsoil can form. When soils lose carbon, they also lose structure, water-holding capacity and nutrient availability. Understanding soil building is thus fundamentally important to future viability of agriculture. Rebuilding carbon-rich topsoil is also the only practical and beneficial option for productively removing billions of tonnes of excess CO2 from the atmosphere”

Under appropriate conditions, 40%-60% of carbon fixed in green leaves* can be transferred to soil and rapidly humified, resulting in rates of soil carbon sequestration in the order of five to 20 tonnes of CO2 per hectare per year. In some instances, soil carbon sequestration rates above 20 tonnes of CO2 per hectare per year have been recorded where there were virtually no ‘biomass inputs’, suggesting the mycorrhizal carbon highway was the primary mechanism for soil building.

A change from annual to perennially based agriculture can double soil carbon levels in the topsoil within three to five years, particularly when the starting point is below 2%. Soil carbon increases of 0.5%-1% could thus be achieved relatively easily with simple changes to land management across the agricultural zones of eastern, southern and western Australia. Almost 60% of the Australian continent is currently used for food production. The resilience of the resource base to climatic extremes will increasingly be of national and international significance in coming decades. Every 27 tonnes of carbon sequestered biologically in soil represents 100 tonnes of CO2 removed from the atmosphere. As a bonus, it also enables more reliable and profitable production of nutritious food.”

Dr Christine Jones, ANU, Australian Farm journal 2008

“The amount of C in soil represents a substantial portion of the carbon found in terrestrial ecosystems of the planet. Total C in terrestrial ecosystems is approximately 3170 gigatons. Of this amount, nearly 80% (2500 GT) is found in soil (Lal 2008).  The soil carbon pool is approximately 3.1 times larger than the atmospheric pool of 800 GT (Oelkers & Cole 2008). 

The goal of increased storage of carbon in soil has received much wider acceptance due to a better understanding of the processes involved in SOC (soil organic carbon) storage, more direct control of these processes through human activities, and the other known ecosystem benefits to be obtained by increasing SOC, including benefits to water quality and increased food security.”


“Applying organic fertilizers, such as those resulting from composting, to agricultural land could increase the amount of carbon stored in these soils and contribute significantly to the reduction of greenhouse gas emissions, according to new research. Carbon sequestration in soil has been recognized by the Intergovernmental Panel on Climate Change and the European Commission as one of the possible measures through which greenhouse gas emissions can be mitigated.

“An increase of just 0.15% in organic carbon in arable soils in a country like Italy would effectively imply the sequestration of the same amount of carbon within soil that is currently released into the atmosphere in a period of one year through the use of fossil fuels,” write Enzo Favoino and Dominic Hogg, authors of the paper.”

Imagine if we were able to divert most organic waste from landfill, convert it to compost and then return this to productive soils! We may as a country be able to become “carbon positive” within a relatively short timeframe!


In Australia up to 40 per cent of the average household garbage bin is food waste.
Australia needs a food waste strategy, Jon Dee – ABC Environment [web]

Approximately two thirds (62 per cent) of all waste landfilled is organic waste. The bulk of which came from the municipal [domestic] stream.

Globally landfills and waste produces 55 million tonnes of methane annually.  This accounts for 16% of human methane emissions.

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