Without a rapid shift to more sustainable ways of dealing with trash, it will be difficult to meet the climate goals set out in the Paris Agreement, a new study suggests. The good news is that such a shift is well within reach technologically, the analysis indicates.
“We found that with the readily existing waste-handling technologies, such as retrofitting landfills, digesting organic waste, and composting organic waste, we can curb global solid waste emissions to net-zero warming by 2050,” says study team member Kok Sin Woon, a sustainability researcher at Xiamen University Malaysia. “However, we need to act immediately, as the results of action need time to manifest.”
Municipal solid waste management hasn’t received much attention as a global warming solution. But it has a lot of potential because decomposition of garbage releases large amounts of methane, a powerful greenhouse gas.
Methane is responsible for about one-third of climate warming. It is more potent than carbon dioxide in terms of warming effect, but much less persistent: its half-life in the atmosphere is about 10.5 years, compared to 120 years for carbon dioxide.
All this means that cutting methane emissions could reduce near-term climate warming – which in turn could make more room in the global carbon budget and buy time to deal with hard-to-decarbonize industries such as manufacturing and long-haul aviation.
The new study is the first global analysis of how reduced methane emissions through better management of municipal solid waste could contribute to climate goals.
In the study, Woon and his colleagues calculated greenhouse gas emissions from trash disposal and treatment facilities from 1990 through 2020 in 43 countries that collectively produce more than 85% of municipal solid waste globally. They also modeled how much trash these countries are likely to produce, and the corresponding greenhouse gas emissions, from 2020 through 2050.
Without any changes to municipal solid waste management, the world’s trash is likely to responsible for the equivalent of 32 to 35 billion tonnes of carbon emissions between 2020 and 2050, the researchers report in the journal Science. But the municipal solid waste sector can only emit the equivalent of 11 to 27 billion tonnes of carbon dioxide to stay within the 1.5 or 2.0 °C warming limits of the Paris Agreement.
“The global solid waste sector is not on track for climate targets,” Woon says – neither under the Paris Agreement nor under the Global Methane Pledge, a promise to reduce methane emissions by 30% between 2020 and 2030 that more than 100 countries have signed on to.
The researchers next analyzed four different strategies for reducing the climate impact of municipal solid waste: breaking trash down in anaerobic digesters and using the resulting biomethane (which would reduce emissions by 70%), halving waste generation (which would yield a 63% reduction in emissions); composting organic waste (which could achieve a 57% reduction); and retrofitting landfills with systems to capture methane (27% reduction in emissions).
No single strategy can achieve a climate-neutral municipal solid waste system, so a combination of shifts will be necessary, the researchers say. Reducing the volume of waste would have the biggest impact in high-income countries, while sending trash to anaerobic digesters would have the biggest impact elsewhere. Together, the two strategies could result in a global waste management system with a negative cumulative climate impact by 2050, they calculated.
Implementing those strategies will likely require a combination of government regulation, economic incentives, and communications tools. “The technologies are there, and it is a matter [of] whether relevant stakeholders will be aware of the seriousness of this issue and take action by implementing the appropriate technologies for waste treatment,” Woon says.
The researchers are now looking more broadly at other environmental impacts of trash, Woon reports. “Waste is a complicated issue.”
Source: Hoy Z.H. et al. “Curbing global solid waste emissions toward net-zero warming futures.” Science 2023.