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Climate Action Accelerator > Solutions > Composting

Composting

  • Waste management: principles and life cycle
  • Waste
  • Food waste

Composting is the natural process by which organic waste is turned into fertiliser over time. Compost is usually made up of plant and food waste, which decomposes into a mixture that is rich in beneficial nutrients and organisms for soil. Composting is a relatively easy and cheap way to produce less waste, reduce methane from landfills, reduce pollution from chemicals, regenerate soil, sequester more carbon in the soil, retain water in the soil, and protect biodiversity.

Why is it important?

Every year, across the world, 1.3 billion tonnes of food is either lost or wasted. In addition to exacerbating hunger and food insecurity, food loss and waste contribute to the three planetary crises that threaten our collective future – climate change, biodiversity loss, and pollution. (1)

Food loss and waste generate up to 10 % of global greenhouse gas emissions, while using land and water resources to produce (unused) food increasingly put pressure on biodiversity. (2) Food waste often ends up in incinerators and landfills. Organic waste composed about 1/3 of the waste in Californian landfills in 2018 (3) and landfill waste is responsible for 11% of global methane production, a powerful greenhouse gas. (4) By reducing food waste, composting reduces greenhouse gas emissions. Waste management also comes at a cost, whether it is for transporting or managing waste, or because of the impact of polluting nature. Globally, billions of dollars are spent on landfills alone. (5)

Composting is one of the best options for managing organic waste while also reducing environmental impacts.  Proper composting of the organic waste we generate in our daily lives – inedible or unconsumed food – can be used as natural fertiliser and reduce the dependence on chemical fertilisers, a main source of soil, water, and air pollution worldwide. Pollution from chemicals has adverse consequences on human health and biodiversity.  For example, overfertilisation contributes to the eutrophication of freshwater systems and coastal areas by encouraging growth of harmful algae blooms and the subsequent formation of dead zones in many parts of the world. (6)

Composting has been practised for centuries by traditional communities and is a central component of regenerative farming and gardening. Compost’s rich mixture of microorganisms and nutrients can significantly improve soil and plant health, with cascading benefits for human and animal well-being. (7)

What is the solution?

Collect food waste from strategic locations on your premises and compost it.

Composting is about speeding up the decomposition process of organic matter by creating a relatively controlled and optimal environment for it. The decomposition of matter is due to microorganisms such as bacteria, microbes, and fungi. Ideally, a compost pile is made up of two thirds of carbon rich elements (dry, woody materials, commonly referred to as “browns”), and one third of nitrogen rich elements (food scraps, commonly referred to as “greens”).  This mix, along with proper amounts of oxygen, ensures the decomposition which results in compost, a fertiliser rich in phosphorus, nitrogen and potassium, all essential for soil health. (8)

Composting can be done on a wide range of scales, going from the individual home composting to community level composting, to industrial scale facilities. It can be left to decompose over time in a dedicated space or used as a fertiliser to grow crops.

There are many ways to make compost: on-site composting, in-vessel composting, vermicomposting, aerated (turned) windrow composting, aerated static pile composting, etc. Choosing a method will depend on your goals, materials, and environment, in particular whether the compost will be used as fertiliser, and on the volume of waste that will be managed. If the goal is to centralize the organic waste for treatment and a later use as fertiliser, a collection service will need to be implemented. (9)

  • Point of attention

    It is also possible to produce compost from animal or human excrements (collected via dry toilets). This is another key ecological solution to reduce water consumption and pollution. But beware, the composting process of faeces is not the same as that of food waste. It is longer, has more risk of spreading pathogens and requires separate management. Under no circumstances should the two processes be confused. Composting locations and times must be separate.

Key facts

1/3

of the food worldwide goes to waste. (10)

28%

of waste deposited in landfills can be composted. (11)

40%

of agricultural greenhouse gas emissions are linked to inorganic fertilisers and manure storage and use. (12)

7.8 million

If everyone in the USA composted, it would be equivalent to removing 7.8 million cars from the road. (13)

14%

Up to 14% of carbon introduced with compost into soil can remain there. (14)

5x

5 times more water can be retained by the soil with compost added than traditional soil. (15)

© Conscious Design/Unsplash.

Key actions

  • #1 Assess the situation, the need and the system

    Assess the amount of organic waste produced, the volume of waste that could be managed for composting, the collection and processing potential, and the end use of the compost produced (internal or external). Evaluate the available space (collection and treatment). Assess the risks, costs, advantages and points of attention. Identify the best system that will suit your needs. The larger the operations, the more investments it will represent, but the greater community benefits it will reap. Hire a professional or do it yourself.

  • #2 Identify the location of the composting bin

    Locate the composting bin on your premises, mutualise efforts with other organisations, join a community compost or hire an external service provider. The ideal compost location is a dry and shady spot. Choose wisely compost sites, at a safe distance from any public facility or water resource. Protect them from unwanted visitors.

  • #3 Collect food waste

    Place organic waste collection bins in strategic locations (cafeteria, break room). Clearly display consistent operating instructions to users along with a list of what to compost or not.

  • #4 Train staff

    Train the people who will be responsible for operating and maintaining the system, from collecting the waste to the compost sites. Create a skilled workforce.

  • #5 Operate and maintain

    Compost needs to be looked after regularly. Mastering the composting technique is a key success factor (or obstacle) to the project. Good ventilation and humidity are critical to a good decomposition process with little odour. It is recommended to turn the pile around once a week during the hot season and every month during the cold season. Water the pile (or add more wet materials) if it becomes too dry and add carbon-heavy browns if it becomes too wet. Take standard safety precautions when handling the waste (mask and gloves). Negative outlooks on composting by local stakeholders can hinder the development of a project.

  • #6 Use or distribute the compost

    Use compost on your premises as a natural fertiliser instead of chemicals. If you don’t garden, create a local partnership (farmer, municipality) to donate or sell the compost.

  • #7 Communicate and raise users’ awareness

    Raise users’ awareness on the importance of composting. The success of the project depends on the good participation of the staff. Organise a zero-waste event or composting workshops. Communicate about the initiative locally, to your partners or donors.

To consider

  • Potential co-benefits

    • Reduction of waste production and landfills
    • Reduction of pollution from chemicals
    • Free fertiliser to dispose of
    • Improved soil health with the use of compost
    • Better water retention of soil and flood prevention with the use of compost
    • Protection of human health and biodiversity
    • Reduced costs of waste management

  • Success conditions

    • Staff awareness raising about the importance of composting
    • Operating instructions of what to compost or not clearly displayed and followed by users
    • Compost regularly maintained
    • Use found for compost

  • Prerequisites and specificities

    • Presence of a place to install the composting bin, or a local community composting place to join
    • Some waste can preferably be avoided because of added risks and difficulties (meat, dairy)
    • Never mix faeces and food waste composting

  • Potential risks

    • Potential disease or infection from handling the waste
    • Can have an unpleasant odour if too wet
    • Can attract animals and insects if meat, dairy or bones are discarded

Success stories

Doctors Without Borders: turning food waste into compost in Zimbabwe

MSF works in Harare to reduce the spread of waterborne diseases. It designed a solution to manage biodegradable waste, like food scraps, which can fill up dump sites and water pipes quickly and is expensive to remove. To turn the organic waste into compost, MSF installed composters and supplied the earthworms needed to transform that waste into biofertiliser, called vermicompost. So, while bio-waste is reduced, organic fertiliser is produced, which can be used for household food gardens or sold for extra income. With the natural reproduction of earthworms within the composter, there is also a market to sell earthworms to people who are new to composting. (16)

ACTED: composting workshops throughout the world

The humanitarian NGO ACTED’s approach goes beyond crisis management, with a pledge for sustainable development and the goal for communities to be self-sustaining. In Lebanon, within the scope of a project involving Le Foyer de la Providence and the European Union (OCHA), ACTED organised composting training and garden management workshops.  The Lebanese University is also involved in the project to produce compost. In Mali, ACTED held similar workshops, tailored for cattle farmers which were taught to use manure in compost. It was later sold to farmers. In Senegal, women received similar technical help from ACTED about composting. (17) (18) (19)

Composting in refugees’ camps in Jordan with Action Against Hunger and GIZ

Jordanian communities are growing rapidly due to Syrian refugees, and so is the waste accumulated in refugee camps. Since 2021, Action Against Hunger has implemented a livelihoods program to improve employment opportunities for vulnerable refugees and host communities, in partnership with the German agency for international development and employment (GIZ), and Azraq municipality in Jordan. The program is focused on the solid waste management sector and has included cash for work opportunities through the establishment of a compost unit meant to support the sustainable management of organic waste. It also was comprised of cleaning campaigns in line with national strategies. Composting plants have been set up at the Karak and Irbid sites, where high-quality compost is produced from organic waste. The production and marketing of certified compost under the responsibility of the municipality has increased in quantity and quality. (20) (21)

Female farmers in Tanzania embrace composting and teach each other

A joint initiative from the Jane Goodall Institute and the Behavioral Change Campaign aims to teach farmers in Tanzania about composting technology and environmental conservation. The BCC has found that women recorded a higher adoption rate on the compost technology compared to male farmers. Some women even stepped into an advisory role for others and provide inspections of other local farms. (22)

Decentralised composting projects in Bangladesh

Waste Concern, a specialised NGO, has been operating in Dhaka since 1995. They noticed that out of the enormous 1.65 million metric tons of solid waste produced annually in the city, more than 80% were organic. They started a community based decentralised composting project, which has since then been replicated in other communities, with land being provided by public agencies and local government bodies. They have managed to avoid more than 18’000 tons of CO2 emissions each year and have generated more than 400 local jobs for the urban poor. To scale-up its model, Waste Concern as a Social Business Enterprise partnered with a for-profit private Dutch company using CO2 emissions offsets from the Clean Development Mechanism (CDM) of the Kyoto Protocol. Waste Concern also established a Regional Recycling Training Centre located in Dhaka, offering training programs to help local officials to undertake full operational activities. This model has already been replicated in more than 26 cities. (23)

Composting in a French hospital

A hospital in Marennes, France, has implemented a local composting strategy with four composters. The organic waste from meals and kitchen scraps is composted on site. This approach is supported by the local government’s Regie des Dechets, within the scope of a territorial plan. The end goal is to bring attention to waste in the hospital and to not only recycle and compost, but also to reduce the amount produced. (24)

Start of city-wide composting project in India

With the main objective of providing an alternative to the burning of leaves in the city, the Citizen Environment Improvement Society, an Indian NGO, has launched a campaign introducing composting at a municipal level in Noida. They have created 20 vermicompost pits at strategic locations such as schools, along with a program to promote individual composting at home. The action is motivated by the local ban on horticulture waste burning but aims to go beyond and educate people about how simple it is to turn organic waste into beneficial compost. (25)

Community level composting in Tanzania

A composting initiative was launched by KIWODET, a community-based organisation in Dar es Salaam, Tanzania. KIWODET managed to successfully implement a composting operation for commercial organic waste. Their additional waste collection and sorting activities also contributed to an increased feedstock control as well as the integration of informal waste collecting activities. They are an example that initiatives can arise from local capacity in developing countries, with ready availability and good compostability of the waste stream. However, their example serves as a reminder that negative consumer attitude and lack of municipal support can hinder the acceptance of compost produced from residential wastes. (26)

Composting facility in Honduras

The city of Comayagua has been running a composting operation, which collects organic matter from all over the city and turns it into compost. They use a mincing machine, and the waste is either put in hot composting piles and regularly turned over or oxygenated through vermicomposting. The compost is used locally and has even helped the mayor’s office to completely stop the purchase of agrochemicals. (27)

Organic waste management and composting center in Buenos Aires

In 2014, the Ministry of Public Space and Urban Hygiene studied the city’s waste and notice that 44% of it was organic. The city implemented a waste management plan with collection routes and organic waste drop points. The organic waste collected is treated in a composting facility, located in the city recycling center. All the compost generated in this center is then used by the Government in the green spaces. This management plans avoids hundreds of tons of greenhouse gas emissions each year. (28)

Tools and good practices

  • Composting manual for cold climate countries, Action Contre la Faim International, 2018

    This manual gives advice on composting and on the implementation of composting project in countries with colder climate. It gives details about many composting methods and has plenty of examples and case studies. It also provides detailed methodologies for planning, implementing, and monitoring composting projects.

    Read here

  • Compost and vermi-fertiliser manual, USAID

    This manual gives a presentation of types of compost and organic fertilizer, along with a detailed methodology about making and tending to compost piles. It also dives deeper into vermicomposting and its technicalities.

    Read here

  • Practical plan for hospital food waste recovery, Biocycle, 2012

    This plan presents a comprehensive food waste program for a typical 1,000 bed hospital. It presents recovery options for wood waste. One of the recovery options is composting on site.

    Read here

  • Composting knowledge tools and documentation, Regeneration

    Regeneration is an organisation working on solutions to the climate crisis and aiming to connect people to the resources, organisations, and tools to implement them. It presents an extensive repertoire of information, technical knowledge, tools, documentation and relevant actors in the field of compost.

    Read here

  • Home composting guide for beginners, World Clean-up Day, 2023

    This guide walks the user through the selection of a composting method best suited for their situation. It also serves as a reminder for the uses of compost, the science behind the process, what to put in in, and common issues faced when composting. It is intended for individual home users, but is perfectly applicable for smaller community projects.

    Read here

  • Organise a composting workshop, CDPNE, 2020

    This guide provides instructions on how to conduct a workshop on composting. It walks the organizer through the preparation and structure of the workshop. Available in French.

    Read here

  • Campus composting manual, Post Landfill Action Network, 2019

    This manual is a step-by-step guide for the implementation of composting on a campus. It reviews the various stakeholders and leadership involved in such a project. It also gives advice on the creation of a strategic plan and the expansion of the activities beyond the school.

    Read here

To go further

  • The benefits of using compost for mitigating climate change, Environment Protection Authority, Australia, 2011

    This report by the Department of Environment, Climate Change and Water of New South Wales, Australia, summarises an extensive and detailed literature review. The report findings support the NSW and Federal government priorities to reduce waste and tackle climate change.

    Read here

  • European Compost Network

    The ECN is a membership organisation with 66 members from 27 European Countries. Members include all European bio-waste organisations and their operating plants, research, policy making, consultants and authorities. Thanks to their members, ECN represents more than 4500 experts and plant operators with more than 45 million tonnes of biological waste treatment capacity.

    Read here

  • International Compost Alliance

    The Alliance is a global network sharing the knowledge, recommendations, and practices of its member organizations. It aims to maximise the recycling of organic wastes and advance the manufacturing of certified, high-quality compost to benefit the environment and society.

    Read here

  • Global waste management outlook, UNEP, 2015

    This lengthy document presents holistic approach towards waste management and gives numerous tools. It highlights the significance of recognizing waste and resource management as a contributor to sustainable development and climate change mitigation. This document gives directions for a way forward on waste management, with composting as part of the solution.

    Read here

  • Results-based financing for municipal solid waste projects, World Bank, 2014

    This report, part of the Urban Development Series, provides examples of Results-Based Financing for MSW projects. It aims to present the challenges faced in the design and implementation of MSW projects. The report also gives recommendations on how to address each challenge. This is a piece tailored for local managers of solid waste and policymakers.

    Read here
Waste management: principles and life cycle
solution area

Waste management: principles and life cycle

Sources

(1) UNEP, “How composting can reduce our impact on the planet”, 2021. Read here.

(2) UNEP, “Food Waste Index Report”, 2021. Read here.

(3) CalRecycle, “Organic Materials Management and Climate Change”, 2018. Read here.

(4) Gloria Dickie, “Landfills around the world release a lot of methane – study”, Reuters, 2022. Read here.

(5) Bruna Alves, “Price of landfilling municipal waste in the U.S. 2020-2021, by region”, Statista, 2023. Read here.

(6) UNEP, “Environmental and Health Impacts of Pesticides and Fertilizers and Ways of Minimizing Them: Envisioning a Chemical-safe World – Summary for Policymakers”, 2021. Read here.

(7) Regeneration, “Compost”. Read here.

(8) Compost Magazine, “The Science of Composting: How Compost Happens”, 2023. Read here.

(9) Regeneration, “Compost”. Read here.

(10) FAO, “Global food losses and food waste – Extent, causes and prevention”, 2011. Read here.

(11) Environmental Resilience Institute, Indiana University, “Composting at home: How to reduce your waste and make your own fertilizer”. Read here.

(12) UNEP, “Environmental and Health Impacts of Pesticides and Fertilizers and Ways of Minimizing Them: Envisioning a Chemical-safe World – Summary for Policymakers”, 2021. Read here.

(13) Environmental Resilience Institute, Indiana University, “Composting at home: How to reduce your waste and make your own fertilizer”. Read here.

(14) Department of Environment, Climate Change and Water NSW, “The benefits of using compost for mitigating climate change”, 2011. Read here.

(15) Environmental Resilience Institute, Indiana University, “Composting at home: How to reduce your waste and make your own fertilizer”. Read here.

(16) MSF, “Reaping the rewards of recycling in Harare, Zimbabwe”, 2022. Read here.

(17) ACTED, “Des solutions innovantes pour la sécurité alimentaire et nutritionnelle en milieu urbain”. In French. Read here.

(18) ACTED, “Soutien aux initiatives communautaires pour un relèvement solidaire”. In French. Read here.

(19) ACTED, “Des acteurs économiques au service de leurs communautés”. In French. Read here.

(20) Action Against Hunger, “Consultant (Final Evaluation of Action Against Hunger Project)”. Read here.

(21) Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH, “Waste disposal with positive effects”, 2021. Read here.

(22) USAID, “Female Farmers Embrace Composting, Teach Others How to Grow Healthy Crops”, 2022. Read here.

(23) Waste Concern, “Waste Concern’s Integrated Resource Recovery Center (IRRC) being replicated by Dhaka City Corporations (North and South)”, 2018. Read here.

(24) Rochefort General Hospital, “Compostage : l’hopital passe à la vitesse superieure”, Vert & Bleu n°52, 2017. In French. Read here.

(25) Sharmila Bhowmick, “NGO launches composting drive in Noida”, The Times of India, 2015. Read here.

(26) Aisa S. Oberlin and Gábor L. Szántó, “Community level composting in a developing country: case study of KIWODET, Tanzania”, Waste Management & Research 29(10):1071-1077, 2011. Read here.

(27) UNDP Latin America and Caribbean, “Composting, a practice that values our waste”, 2023. Read here.

(28) María Agustina Ferrari, “Organic Waste Management and Composting Center”, Construction21 France, 2021. Read here.

 

Cover photo © Gabriel Jimenez/Unsplash.

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