Compost Magic

Written by our intern Tapiwa Muzite

If you are reading this you probably already love compost.  And you know that compost is much more than that lovely stuff you make at home and feed to your soil.  We thought we would really delve into the benefits of compost for our soil, our climate and our plants.

Please share this with your non-composting friends (maybe they will finally get your passion!).

• Composting results in less organic waste finding its way to the landfill thereby reducing the carbon dioxide equivalent (CO2e) emissions that might have occurred as a result of the collection and transportation of the organic waste from its point of generation to the landfill and the rotting of that waste in the landfill. For each tonne of food waste composted, 232kg CO2e of emissions are saved vs. landfilling. Composting also reduces waste disposal costs for municipalities and extends landfill life as food waste can occupy up 1.5m3 for every tonne of food waste.

• Adding compost to soil increases its Soil Organic Matter (SOM) content.  This helps improve soil stability by as much as 29% to 63%. SOM is crucial for improving the water holding capacity of soil. Adding compost to clay soils improves their water absorbing capacity as it opens up air pockets.  Similarly for sandy soil, adding compost reduces drainage rates and improves its water holding capacity by as much as 50%.

• Compost can result in significant water saving in irrigated lands. Australian research showed that adding 50 tonnes of compost on 1 hectare (or 5kg per 1m2) of agriculture land saved 200,000 litres of irrigation water per hectare per year.

• Compost should be seen as a key climate change mitigation strategy.  Adding organic matter (compost) to soil removes carbon from our atmosphere. Ryals and Silver showed that applying 76m3 of compost on 1 hectare of California rangelands removed carbon from the atmosphere and stored it into the soil at a rate of 1 tonne per hectare per year over three years.

• Not only does healthier composted soil help retain water and absorb carbon, compost also stays in the soil for a long time thus having a triple benefit.  Over half of compost’s carbon will stay in the soil for over a year; and up to 16% for 100 years.

• Compost helps reduce the use of inorganic fertilisers in agriculture as nutrients for example nitrogen, potassium and phosphorous required for plant growth are also available in compost. Compost holds and slowly release nutrients thereby retaining nutrients for plant uptake and reducing the washing down of nutrients beyond the root zone as water soaks down into the soil.

• Compost helps build the soil-food-web by increasing the different types of microbes in the soil as well as their numbers.  Fertile soil contains  up to 26 million beneficial bacteria.  Adding compost to the soil will increase the population of beneficial bacteria and by up to 16 times – as these bacteria are key in making nutrients available to plants this is a real boost to the vitality of your plants.

• Compost can even be used to treat soil contaminated by petroleum hydrocarbons (e.g. gasoline, diesel and oil), pesticides and herbicides.  A 70% input of compost to contaminated soil has been proven to eliminate all toxins. This is a lot cheaper than removing all the contaminated soil and moving it to a hazardous waste landfill site.

• Compost makes our plants healthier.  It reduces the occurrence of pathogenic diseases and thus can radically reduce the use of fungicides and bactericides in agriculture and landscaping. Application in turf grass has shown that compost suppresses pathogens that lead to damping-off, snow mould, fusarium and brown patch.

1. Chen, S., (2015). Evaluation of compost topdressing, compost tea and cultivation on tall fescue quality, soil physical properties and soil microbial activity. University of Maryland, College Park.
2. Andersen, J.K., Boldrin, A., Christensen, T.H, Scheutz, C., (2012). Home composting as alternative treatment option for organic household waste in Denmark: an environmental assessment using life cycle assessment-modelling. Waste Manag. 32, 31-40
3. DEFRA/DCC, (2016). 2016 UK Government GHG Conversion Factors for Company Reporting. Department of Energy and Climate Change (DECC) and the Department for Environment, Food and Rural Affairs (DEFRA). UK
4. Martínez-Blanco, J., Lazcano, C., Christensen, T.H., Muñoz, P., Rieradevall, J., Møller, J., Antón, A., Boldrin, A., (2013). Compost benefits for agriculture evaluated by life    cycle assessment. A review. Agron. Sustain. Dev. 33,721-732
5. Recycled Organic Unit (2006). Life cycle inventory and life cycle Assessment for windrow composting systems, Recycled Organics Unit, University of New South Wales. Department of Environment and Conservation, Sydney, NSW, Australia.
6. Giusquiani, P.L., Pagliai, M., Gigliotti, G., Businelli, D., Benetti, A., (1995). Urban waste compost: effects on physical, chemical and biochemical soil properties. J. Environ. Qual. 24, 175–182.
7. Ryals, R. and Silver, W, L., (2013). Effects of organic matter amendments on net primary productivity and greenhouse gas emissions in annual; grasslands. Ecological Applications. 23, 46-59
8. CARB, (2011). Methods for estimating Greenhouse Gas Emission reductions from compost from commercial organic waste. Planning and Technical Support Division, California Air Resources Board.
9. EPA, (1998). An analysis of composting as an Environmental remediation technology. United States Environmental Protection Agency.