COP28 : The significant potential of better waste and resource management for climate mitigation

Numbers do matter, and the Intergovernmental Panel on Climate Change (IPCC)’s statement in their 2013 Fifth Assessment Report (AR5) that the waste sector is responsible for around 3% of global greenhouse gas (GHG) emissions has led to a common perception that waste management has little to contribute to the mitigation of climate heating. But that perception is WRONG. This article sets out the case that, although measurement is difficult and uncertain, and the ‘system boundary’ is a bit ‘fuzzy’, we can still, using IPCC terminology, have high confidence that the overall contribution of better waste and resource management to the mitigation of climate heating is significant. Whether that number is 15%, 20%, 25% or some other number, it does not affect the conclusion: the contribution is significant, and action is needed NOW to ensure that better waste and resource management, and improved resource efficiency, are included as a core part of every country’s nationally determined contribution (NDC).

To avoid double counting, IPCC partition the economy into sectors, with the ‘waste sector’ confined to end-of-pipe waste management. So the top two segments of Figure 1 show the direct emissions of greenhouse gases (GHG) using that narrow definition. More than 90% of the waste sector’s direct contribution to climate heating is methane from the anaerobic degradation of organic wastes, mainly from dumpsites and solid waste landfills but also from wastewater treatment. Methane is a ‘short lived climate forcer’ (SLCF) which is at least 28 times more powerful than CO₂, and up to 80 times for the first 20 years after release into the atmosphere.

But solid waste management is evolving into waste and resource management and towards a circular economy, with the emphasis moving to the 3Rs of reduction, reuse and recycling. Each of those can contribute to climate mitigation by displacing GHG emissions elsewhere in the economy: IPCC credits those indirect savings to the upstream sector which put the product or material on the market, or which generated the displaced energy. Even the most advanced high-income countries still have much potential for climate mitigation from the 3Rs.

IPCC’s AR5 uses 2010 data. The first environmental control legislation was introduced in high income countries from the early 1970s, which gradually increased the level of control for solid waste landfills. The early operational controls (the ‘3Cs’ – confine, compact, cover) resulted in anaerobic controlled disposal sites, (the basic control level now set to meet SDG indicator 11.6.1), thus increasing methane generation. The next step to improve controls collected the landfill gas, often using flares to convert methane to CO₂ which provided significant climate mitigation. Full control or environmentally sound management (ESM) recovered energy from the gas, thus offsetting part of the already much mitigated GHG emissions. These environmental controls were supplemented from 1990 by moves to divert organic wastes from landfills, explicitly to reduce GHG emissions. So by 2010, the estimated 3% direct emissions from the waste sector, as measured by AR5, reflects more than 30 years of effective mitigation efforts by many high income countries.

Data on GHG emissions goes back to 1990, set as the base year under the UN Framework Convention on Climate Change (UNFCCC) adopted in 1992. To take the UK as a case study, by 1990 88% of municipal solid waste was still disposed of to landfills. Table 1 shows the development of the waste sector’s contributions to total UK GHG emissions from 1990 to 2021; the 1990 baseline already reflected mitigation of landfill emissions due to improved controls with either flaring or gas recovery.Landfill emissions remained relatively stable through the 1990s, before sharp reductions from 2000 which reflect the introduction of full ESM controls under the EU Landfill Directive, as well as EU mandated diversion of waste from landfills as an explicit climate mitigation measure. In 1995, landfills alone accounted for 9.3% of total national GHG emissions, reduced to 3.2% by 2021. This sharp reduction means that the solid waste sector has out-performed other larger sectors, contributing 20% of the overall national mitigation achieved between 1990-2010. This illustrates the potential of the waste sector to provide ‘quick wins’.

Some examples from specific studies in developing countries support the hypothesis that the % contribution of solid waste management declines over time as control over landfills improves and wastes are diverted to other management methods. A lifecycle analysis (LCA) of three upper middle income countries in 2005/07[ii] showed that methane from landfills accounted for 6.8-13.5% of total national CO₂-eq emissions in Tunisia and 7.2-10.5% in Turkey, with the ranges reflecting assumptions of 50 to 100% disposal in controlled (anaerobic) landfills without gas control; Mexico showed a range of 6.2-8.0%, reflecting 100% controlled landfills, with gas capture in the range of 100% (lower estimate) to 20%. Both these and the UK examples would suggest that, when municipal solid waste (MSW) is collected and disposed of in basic controlled landfills (i.e meeting SDG target 11.6), the baseline contribution to national GHG emissions is around 10%.The composition of MSW in developing countries is predominantly organic, unlike high-income countries. Results for specific cities do suggest that direct contributions from the waste sector can be even higher. Two examples come from the C40 Cities[iii] Deadline 2020 programme to prepare climate action plans. In Accra, Ghana, the 2015 baseline showed waste as the largest emitting sector at 44%, with solid waste contributing 30%, split into 17% controlled landfill, 10% open dumping and 3% open burning and other incineration. In Quezon City, Philippines the waste sector contributed 19% of total emissions in 2016, with 12.9% from solid waste management.

Open burning of waste was omitted from IPCC estimates up to AR5 due to data not meeting their quality threshold. Considerable recent research has tried to plug that gap. Some early estimates assumed high levels of open burning, which when combined with newly measured emission factors and high CO₂eq values gave rise to estimates of a 2-10% contribution to global GHG emissions[iv]. However, using a more recent re-estimate of open burning levels and the lower IPCC AR6 CO₂eq values, that estimate is now reduced to 0.5-1.0%[v].

Using recycled materials as secondary raw materials in industrial production to displace virgin materials significantly reduces GHG emissions, both by reducing direct energy consumption in the production process – e.g. in glass production by 35%, paper and steel over 50%, plastics over 70% and aluminium over 90% – and by the indirect upstream avoidance of mining, processing and transport of primary raw materials. The net savings from recycling are particularly dependent on the local conditions and assumptions in the life cycle assessment.

Returning to the UK case study, recent reports estimate that sorting and recycling alone helped avoid 45 MtCO₂eq emissions in 2018[vi] (9.7% of total national GHG emissions of 465Mt); and that food waste accounts for 36 Mt[vii](7.7%). The latter is similar to an estimate that 9% of global GHG emissions are used to grow food that are thrown away without being eaten[viii]. Food waste prevention is explicit in the SDGs as Target 12.3, but is only one of many commodities or products where prevention would make large GHG savings.

So, the best estimates, that the range of savings available from recycling and energy recovery, and from waste prevention, which are each 5-10% of global GHG emissions, are quite conservative.

The world is facing a global waste emergency[ix] characterized by a lack of access to municipal solid waste (MSW) collection for 2.7 billion people and the alarming statistic that almost 40% of collected waste ends up in uncontrolled disposal or is openly burned[x]. This crisis is ongoing and threatens to worsen in low- and lower-middle income countries as populations grow, urbanization accelerates, and waste generation per capita increases with economic development. Without action, many cities in Africa and South Asia are projected to see their waste generation double every 15-20 years[xi]. To tackle this emergency, it is essential to extend MSW collection to all, while phasing out open dumps and open burning (SDG 11 sustainable cities – indicator 11.6.1).

Tackling this “waste emergency” will have benefits across many sustainable development goals (SDGs). Those most impacted by unmanaged or mismanaged wastes are the most vulnerable in society (SDG 1.4 – basic services for all; SDG 10 – reduce inequality). The local benefits often focus on public and individual health (SDG 3) and the environment (SDG 6.3 – improve water quality by eliminating dumping; SDG 12.4 – environmentally sound management (ESM) of all wastes). Global benefits include significant contributions to prevention of marine pollution (SDG 14.1) – achieving SDG 11.6.1 would halve the mass of plastics reaching the oceans[xii] – and to climate mitigation (SDG 13).

To make SDG 11.6.1 achievable, both logistically and financially, it is necessary to work in parallel to stem the growth in waste quantities, particularly in cities. Reducing food waste and losses along the supply chain (SDG 12.3) will also help to end hunger (SDG 2). Increasing recycling rates (SDG 12.5) will divert waste from landfill and reduce investment costs. Separating the dominant organic fraction at source and collecting that separately as a clean feedstock for organics recycling will promote sustainable, local, small-scale food production (SDG 2.3 & 2.4), create jobs (SDG 8.5) and slash methane generation from the residual wastes (SDG 13). Increasing dry waste recycling rates can be achieved by building on the existing informal recycling sector and integrating them alongside the MSW management service. Separating wet organics at source makes the remaining waste much cleaner, enabling the recyclers to work in cleaner and healthier conditions, and leading to increased quantity and better quality of materials for recycling and improved, decent livelihoods (SDG 8.5).

Clean, source separated organic feedstock is critical to organics recycling, as it allows use of compost and digestate for food crops, or indeed direct feeding to animals or breeding insects such as black soldier flies as a source of protein or fertiliser, without concerns over contamination with either plastics, chemicals or heavy metals. Municipalities in the global South must be wary of anyone selling technologies that can ‘magically’ separate the organic fraction cleanly from mixed waste – any product derived from mixed waste is at best a ‘compost-like’ or ‘bio-stabilized’ material, which should be destined for use as municipal landscaping (e.g. alongside roads) or as soil cover on a landfill, and not be used for food crops.

While the benefits of MSW management are both local and global, the costs are typically considered to be a local responsibility. The problem is that even the costs of basic services to meet SDG 11.6.1 (95+% mixed waste collection and controlled disposal) are unaffordable in many towns and cities in low- and middle-income countries. To maximise the climate benefits, actions beyond SDG 11.6.1 are needed, to divert waste from landfill through separation at source to increase both organics and dry waste recycling, and to collect and control landfill gas. Local cost recovery needs to be complemented with income from extended producer responsibility (EPR) schemes, where the supply chain who place packaged products on the market bear the full costs of collecting, recycling and properly disposing of their packaging which forms part of MSW. Also, the international community needs to recognise the global benefits by targeting both climate finance, and ‘plastics finance’ under the plastics treaty, to support the transition to sustainable MSW management practices.

Official development finance first supported MSW projects in the 1970s, but soon found that sustainable solutions required more than the capital costs of equipment. This led to the development of the integrated sustainable waste management (ISWM) framework in the 1990s, which emphasises the need to consider all the technical aspects – collection, treatment and disposal, and the 3Rs; and all the governance aspects – the stakeholders including the users and the service providers, financial sustainability, the national policy framework and local institutional coherence. Local capacity building is an essential component of most initiatives. There are lots of cautionary tales about failed projects, including full control landfills reverting to open dumps because the city could not afford the running costs. The old Clean Development Mechanism (CDM) under the Kyoto Protocol was used to provide an income stream from utilization of landfill gas, which provided a powerful incentive for cash-strapped cities to fund proper operation of their new landfill sites. The closure of CDM left a large gap.

What is needed now is a proper ‘joined-up’ approach, where all the different stakeholders – local and national, international development, climate change, plastics pollution, waste producers and the waste and resource sectors – work together to enable win-win-win solutions across multiple SDGs. Climate finance has a critical role to play, but does need to be designed to accommodate some specific characteristics of sustainable waste projects. These always go beyond just equipment. The waste needs to be collected, and preferably separated at source. Many recycling (and organic waste diversion) projects are community based. Project revenues will never cover costs – and recycling revenues should accrue to the informal recyclers not to ‘the project’. Even controlled or ESM landfill projects are often in the mid $5-95 million range that is less interesting to development agencies. Funding needs to reach communities, non-governmental organisations (NGOs), municipalities and regional governments – this constrains development agencies who must work via national governments. The cross-cutting nature of the benefits can appear to conflict with 'additionality', the criterion that projects need to provide GHG mitigation benefits that would not have happened otherwise. Calculating and monitoring the mitigation achieved is challenging, which can translate into high transaction costs for accreditation and verification.

Addressing the global waste emergency is not only a local responsibility but also a global imperative. By adopting sustainable waste management practices, countries can achieve rapid and deep reductions in direct GHG emissions while also realizing significant GHG savings through both organic and dry waste recycling. This multifaceted approach tackles all four quadrants in Figure 1, making it a comprehensive strategy to combat the global waste crisis and move towards a more sustainable future.

We strongly urge global leaders to integrate sound waste and resource management into their nationally determined contributions. Alongside significant potential for climate mitigation at a reasonable cost, such actions will also facilitate equitable progress across a broad range of the Sustainable Development Goals.

Authors: David C Wilson is a lifelong waste and resource management consultant, Visiting Professor at Imperial College London and ISWA Honorary Life Member. Carlos Silva Filho is ISWA President. Aditi Ramola is Technical Director at ISWA.