The Climate Action Accelerator estimates the Greenhouse Gas (GHG) emissions of the humanitarian sector globally in 2022 to be approximately 35.3 megatonnes of carbon dioxide. This compares to the emissions of a European city with approximately 4.6 million inhabitants. The sector’s contribution to climate change cannot be neglected. To fulfil and acknowledge this responsibility, the humanitarian sector has launched various initiatives to reduce its carbon footprint. By early 2025, 471 humanitarian organisations had signed the Climate and Environment Charter for Humanitarian Organizations, stating their willingness to rapidly reduce GHG emissions. While the largest emissions in the humanitarian sector are linked to purchased goods (32%), cash-based interventions (29%) and purchased services (14%), the contribution from waste is not known or quantified. Nevertheless, waste does generate GHGs and in line with the Climate and Environment Charter and the Do No Harm principle P.1, GHG emissions from SWM in humanitarian response must be addressed and minimised.

Impact of SWM on Climate Change

The transport, treatment and disposal of solid waste generates greenhouse gases and airborne pollutants, contributing to climate change. Emissions come mainly from burning or decomposing waste and, to a lesser degree, the handling (transport) of the waste because of its use of fossil fuels. The largest source of GHG waste emissions is landfill methane (CH₄), which is generated from the anaerobic decomposition of organic materials. Uncontrolled burning of waste emits black carbon, nitrous oxide (N₂O), and carbon dioxide (CO₂) Other greenhouse gas emissions are halogenated compounds found in e-waste, such as refrigerants and insulating foam in fridges and freezers, which can be released when e-waste is inadequately disposed of or dismantled. 

Global Warming Potential measures the potency of greenhouse gases. It is referenced to the potency of CO₂ and measures are expressed as a CO₂ equivalent. All waste emissions mentioned above – methane, nitrous oxide, black carbon and halogen-containing compounds – are much more potent than CO₂. Both methane and black carbon are Short-Lived Climate Pollutants (SLCPs), meaning they have a relatively short atmospheric lifetime. Reducing SLCPs is important as they have a significant impact on near-term global warming and cause other negative effects. For instance, black carbon is a component of fine particulate matter (PM_2.5) and can cause respiratory health issues; methane contributes to ground-level ozone formation which adversely affects public health and ecosystems. 

Methane emissions from uncontrolled disposal or open dumping U.10 and landfills U.9 have received the most attention in waste and climate discourse. Methane is generated during the anaerobic degradation of organic matter and is most prominent in disposal sites. Engineered, sanitary landfills are designed and constructed to capture and use methane. However, such landfills are rare in low and middle-income countries and humanitarian settings. In unmanaged disposal sites, methane instead flows by the path of least resistance and escapes directly into the atmosphere.

Black carbon is less well documented and its impacts are not well understood. Open burning (i.e. incomplete combustion) U.11 is the main source of black carbon in waste management. Black carbon is also emitted from waste transportation, particularly when older vehicles and lower-quality fuels are used. Black carbon emitted into the atmosphere can travel long distances across the planet and settle on the surface of sea ice and snow. There, it accelerates melting by absorbing, rather than reflecting, sunlight, further contributing to global warming. Black carbon emissions from biomass burning are much lower than the methane emissions generated from waste. However, the significantly higher global warming potential of black carbon (its CO₂ equivalent) makes it a significant short-lived climate pollutant. 

Mitigation of GHG Emissions from Solid Waste in Humanitarian Settings

Phasing out open burning U.11 and diverting biodegradable wastes from disposal reduce GHG emissions from waste in humanitarian settings. Transitioning from end-of-pipe waste management towards resource management and a circular economy and enhancing waste prevention P.1, recycling and recovery could further reduce GHG emissions.

The most straightforward way of reducing black carbon emissions in humanitarian settings is to stop open burning U.11 in all its forms and locations. This requires an understanding of the reasons for open burning followed by training, awareness and appropriate alternatives to prevent the practice. Waste emissions are also reduced by diverting the organic biodegradable fraction of waste from disposal into organic waste treatment and reuse (T.1 to T.5), significantly reducing GHG emissions and eliminating methane emissions at the disposal site. Additionally, the recycled organic fraction can substitute for other products (such as fertilisers) avoiding emissions generated by their production. For example, diverted biodegradable waste generates compost T.1 which can partially substitute chemical fertilisers, reducing GHG emissions from fertiliser production and increasing carbon sequestration and storage in soils. Similarly, anaerobic digestion T.3 of waste generates biogas and digestate. Biogas is a carbon-neutral substitute for fossil fuels. Digestate can substitute chemical fertilisers and contribute to carbon storage. Black soldier fly treatment T.4 produces insect protein for use as animal feed and frass, replacing fish meal and/or soya bean, preventing their GHG emissions. Frass can substitute fertilisers and contribute to soil carbon sequestration.

Making secondary materials out of recycled paper, glass, metals, plastics T.7, textiles and waste electrical and electronic equipment avoids emissions that would have been generated by primary extraction and production. For glass, plastics, ferrous metal, textiles and aluminium, studies show that recycling yields overall net greenhouse gas flux savings of between about 30 kg CO₂e (for glass) and 95 kg CO₂e (for aluminium) per tonne of municipal waste, compared with the disposal of untreated waste. 

Overall, reductions in emissions of greenhouse gases associated with the transportation of waste, residues and recovered materials are minor compared to the much bigger greenhouse gas fluxes in the system, such as those resulting from preventing production and landfill gas emissions. Nevertheless, they can still be reduced by, for example, minimising travel distances, prioritising clean fuels and vehicles with efficient combustion and practising fuel-efficient driving.

Impact of Climate Change on SWM Systems and Strategies for Adaptation and Resilience

In some regions, climate change is expected to cause more frequent extreme or slow-onset events such as increased rainfall and wind speed or droughts. The infrastructure of solid waste is vulnerable to new climate patterns; it is rarely designed to be resilient to climate change phenomena and its lifespan can be shortened by these stresses. Excessive moisture and rainfall combined with improper design and poor maintenance may lead to severe landslides at disposal sites, more frequent flooding and disruption of roads.  More wind and dry weather facilitate waste fires which emit hazardous gases, particulates and embers, further spreading fire during drought. Pests and pathogens can proliferate with increased temperatures and rainfall, potentially threatening the health of waste workers and residents. A better understanding of climate change effects and site-specific risk assessments are needed to reduce risk, better respond and improve the resilience of systems and their operation and maintenance.