Organic waste management reveals methane reduction opportunities in Uganda

Effective climate mitigation strategies require simultaneous actions targeting Carbon Dioxide (CO₂) and Short-Lived Climate Pollutants (SLCPs), such as methane (CH₄), Black Carbon (BC), Tropospheric Ozone (O₃) and Hydrofluorocarbons (HFCs). Tackling SLCPs and CO₂ across various sectors is essential to tackle near- and long- term warming¹. The waste sector in particular plays a significant role in climate mitigation as action in this sector reduces both short-and long-term climate pollutants contributing to combating climate change^2,3,4,5. Addressing organic waste is particularly crucial for reducing CH₄ emissions, as dumpsites and landfills generate approximately 20% of direct anthropogenic methane emissions through the anaerobic decomposition of organic waste^3,6.

Beyond climate mitigation, environmentally sound waste management reduces environmental impacts while also contributing to the achievement of all Sustainable Development Goals (SDGs) by supporting good public health and well-being, reducing pollution, fostering the circular economy, conserving natural resources⁷ and creating decent and green jobs⁸. Reducing waste and improving its management are crucial for building more climate-resilient, adaptative and equitable societies⁹, especially in the Global South in which current and projected increasing quantities of waste generation worsens the already critical situation of waste management systems and associated impacts^3,10,11,12. While efforts to prevent waste generation in the Global North still remain limited, the region has successfully managed rising waste quantities through advanced waste management infrastructure³. Although waste management practices in the Global North have proven successful, directly transferring them to the Global South is not appropriate due to significant differences in waste characteristics, socio-economic development, infrastructure availability, reliance on the informal sector and financial constraints¹³.

Despite these challenges, the Global South offers an opportunity to change the paradigm from adopting Global North treatments and centralized waste management systems to an approach that combines centralized and decentralized systems, placing communities at the core of waste management strategies^14,15,16. Decentralized waste management systems are particularly relevant in rural areas in the Global South, where waste collection and management services are often scarce¹¹. These systems offer communities the opportunity to engage in initiatives and directly benefit from sustainable waste management approaches while addressing the climate crisis.

The combination of centralized and decentralized management of organic waste is remarkably significant in the Global South, as food waste is expected to depict the highest increases in South Asia, sub-Saharan Africa, and South America¹⁷. This in combination with the fact that over 1.5 billion people, especially in rural areas in the Global South, lack access to clean energy for cooking and lighting¹⁸, and access to fertilizers remains limited, especially in Africa, where soils are low in fertility¹⁹, makes organic waste management an important player in providing additional sources of energy, fertilizers and animal feed in these regions. Africa’s waste collection rate is only 36%, with more than 90% disposed of in uncontrolled dumpsites or through open burning^10,20,21. Notably, 19 of the world’s 50 largest dumpsites are located in Africa, primarily in Sub-Saharan countries, where 57% of waste is organic and 13% plastic²². However, just 4% of Africa’s waste is recycled, despite the potential for up to 80% recyclability²¹.

While a number of studies have examined the climate mitigation potential of the waste sector at a global^3,4,23 and national levels, particularly in the context of the Biennial Update Reports to United Nations Framework Convention on Climate Change (UNFCCC)²⁴, Nationally Determined Contributions (NDCs) under the Paris Agreement²⁵ and Global Methane Pledge²⁶, the assessment of the relevance of waste management to adaptation, resilience and equitable societies remains underexplored. In Africa, addressing organic waste is particularly important as a climate mitigation strategy because the municipal waste sector contributes approximately 35% of the region’s methane emissions, estimated at 4.7 million tons of CH₄, equivalent to about 160 million tons of CO₂_eq²⁷ In South Africa, for example, studies estimated that the waste sector contributes more than 19 million tons of CO₂eq annually, representing 4.1% of the country’s total GHG emissions. In 2020, the sector accounted for 36.5% of total methane (CH₄) emissions, with solid waste disposal contributing 79.2% of these emissions. Using the WROSE and GAINS model, it turned out that by combining landfill gas recovery with electricity generation, recycling, and anaerobic digestion was the most effective option for reducing GHG emissions while maximizing waste diversion and resource recovery from biogenic food waste²⁸.

In this article, our objective is to bring together and demonstrate the cascade of benefits of addressing the organic waste sector for climate mitigation, adaptation, resilience, and equitable societies, using Uganda as a case study. Uganda has a rapidly growing population and urbanization rate, with major urban centers including Kampala, Gulu, Mbarara, Jinja, and Mbale. Uganda is administratively divided into 135 districts and the Kampala Capital City. Rapid urban growth has increased pressure on municipal services, particularly waste management systems, which are often characterized by low collection coverage, open dumping, and inadequate disposal infrastructure²⁹.

Urban areas in Uganda face significant waste management challenges, with nearly half of the waste remaining uncollected, resulting in a collection rate of only about 50%^22,30. This shortfall has led to open dumping in drains, unauthorized dumpsites, and widespread burning, particularly in Kampala and its metropolitan area, which struggle with high population density and inadequate infrastructure^22,30. In Kampala City alone, approximately 2000–2500 tons of waste are generated daily, yet only about 50% is either collected or improperly disposed of³¹. This contributes to severe air and soil pollution and greenhouse gas emissions. Notably, over 70% of the waste generated in Kampala is organic and could be composted or used to generate energy. However, instead of being utilized, it decomposes in landfills, releasing methane into the atmosphere^32,33. Organic waste composting remains limited, mainly championed by small and medium enterprises that process compost and energy.

Although Uganda received international support to enhance organic waste management infrastructure, including 12 CDM composting projects commissioned by the World Bank in 2012 (Uganda Municipal Waste Compost Programme), most of these initiatives are now non-functional, with the few operational ones performing sub-optimally due to inadequate funding and limited technical capacity³⁴. This situation once more highlights that technology transfer efforts that ignore local contexts are at high risk of failure.

Here we argue that to develop effective, equitable and implementable interventions and policies, it is crucial to adopt an approach centered on people’s realities and needs. People should have the right to shape interventions, so they can effectively adopt, respond to and benefit from them. We adopted a co-development methodology, an approach combining participatory and qualitative methods, to shape Uganda’s National Strategy for Reducing SLPCs emissions from the Organic Waste Sector, while also exploring and quantifying opportunities to enhance adaptation, resilience, and promote more equitable communities across the country. Combining co-design with modeling is methodologically valuable because it integrates local stakeholder knowledge into the design of mitigation scenarios while using modeling to quantify their potential GHG reduction, waste diversion, and resource-recovery impacts. This approach reduces the risk of producing technically optimal but socially or institutionally unrealistic recommendations. It is particularly relevant for organic waste management in African countries, where data gaps, informal practices, infrastructure constraints, and governance capacity strongly influence implementation³⁵. We extended the Greenhouse gas and Air Pollution Interactions and Synergies (GAINS) model to include Uganda’s waste sector and applied our most recent methodology^3,36, to estimate CH₄ emissions and mitigation potentials at both national and regional levels under a Reference Scenario, With Existing Measures Scenario and three mitigation scenarios co-developed during three stakeholder workshops. These scenarios incorporate a comprehensive review of the current state of organic waste generation and management in Uganda, an evaluation of the existing policy framework and reflect the collaborative approach to identify actionable strategies for reducing emissions in Uganda’s waste sector, using 2020 as the baseline year, with the assessment covering the period from 2005 to 2050. The scenarios are designed not only to represent the methane mitigation potential of organic waste but also to meet people's needs for fertilizers, energy for cooking and lighting, and animal feed. Here we show that combining multiple organic waste management interventions could avoid up to 1.3 million tonnes of carbon dioxide equivalent methane emissions annually by 2035, produce sufficient compost to fertilize approximately 271,102 hectares of maize and generate enough biogas to support the preparation of about 628,000 meals each year, strengthening climate resilience, food security and energy access.

The paper first presents the results of the co-design process, then the modeling framework and finally the scenario comparison. It then discusses the analysis of the co-benefits and concludes with the final remarks. The methodology section is presented at the end of the paper.