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Increasing amounts of municipal solid waste and ineffective waste management systems threaten the environment and contribute to global warming. Yet the waste sector is often neglected in discussions about climate change and air pollution. A new study by IIASA, in which BOKU was involved, shows for the first time how closed-loop systems in waste management can help to effectively reduce greenhouse gas emissions and air pollutants.

Municipal solid waste is what we commonly refer to as rubbish - the everyday items that we continuously throw away. The amount of waste generated globally each year has increased exponentially in recent decades, largely due to population and economic growth and the resulting changes in production and consumption patterns.

One third of the global waste mountain generated each year is produced by about one sixth of the population (high income countries). However, only about 13% is recycled and 5.5% composted. The lack of adequate facilities to manage these large volumes of waste - especially in low-income countries - often leads to environmental and health damage, including the emission of toxic pollutants and greenhouse gases into the atmosphere.

First global study

In the first global study of its kind, IIASA researchers, together with a scientist from the University of Natural Resources and Applied Life Sciences, Vienna (BOKU), have taken a close look at the waste sector. The study, which has just been published in Nature Communications, examined 184 countries and regions, differentiating between urban and rural settlement areas. The research approach is novel in that it applies Shared Socioeconomic Pathways (SSPs) - a set of scenarios describing alternative socioeconomic developments up to 2100 - to the waste sector and assesses the potential for reducing greenhouse gas and air pollutant emissions by comparing baseline and mitigation scenarios up to 2050.

"We wanted to examine future trends in municipal waste generation and analyse the impact on greenhouse gas emissions and air pollution if waste management systems are maintained at current levels by 2050. We then assessed the extent to which it would be possible to reduce waste and associated emissions if circular waste management systems were introduced under the various SSPs. This approach also helps us to understand how different global developments hinder or accelerate the scope and pace of circular economy system adoption and what impact this has on emissions," explains lead author Adriana Gómez-Sanabria, a researcher in the IIASA Environmental Management Research Group and a PhD student at BOKU.

Circular economy is a sustainable system where waste generation is minimised, waste collection systems reach the entire population, open burning of waste and disorderly dumping of waste are eliminated, waste is kept out of landfills, materials are reused and recycled and, as a last resort, waste is burned efficiently to generate energy.

Scenario for curbing waste incineration

For example, by comparing different scenarios, the researchers found that the Sustainability Scenario (SSP1) - a scenario that envisions a world in which more inclusive development is prioritised while respecting environmental limits - could provide significant and earlier co-benefits compared to scenarios in which inequalities are reduced but pollution control measures focus on treating pollutants in a separate process after they are generated. In this scenario, the researchers estimate that it would be possible to eliminate open burning of waste before 2050, thereby eliminating this source of air pollution.

Although it will not be possible to completely eliminate methane and CO emissions from MSW, the researchers point out that, based on the fact that the maximum technical abatement potential worldwide is estimated at around 205 million tonnes of methane in 2050, reducing emissions from MSW could account for almost a quarter of this. This highlights the need for swift and decisive action to reduce waste and keep it out of landfills, increase reuse and recycling, and promote carbon capture and storage technologies.

The researchers found that different socio-economic assumptions underlying each SSP lead to significant differences in future municipal waste streams. They assume that the lowest amounts of solid waste are expected in SSP3 (a scenario in which countries focus on achieving energy and food security goals within their own regions at the expense of broader development) and SSP4 (a scenario characterised by high inequality) due to slow economic growth and high inequalities between regions.

The results also suggest that lower purchasing power in low-income regions limits the purchase of goods and thus reduces the amount of MSW generated. In contrast, the highest MSW generation is expected in the SSP5 scenario. This scenario describes a world that relies on competitive markets, innovation and participatory societies to achieve rapid technological progress for sustainable development, and is associated with a corresponding steep increase in income and urbanisation rates.

Waste reduction coupled with circular economy

According to the authors, waste reduction coupled with the adoption of circular economy systems will provide a wide range of benefits, including the reduction of greenhouse gas emissions, air and water pollution, while supporting the achievement of the Sustainable Development Goals (SDGs). For example, SDG target 6.3, which aims to improve water quality by reducing pollution, stopping dumping and minimising the release of hazardous chemicals and materials by 2030, can only be achieved through more ambitious municipal solid waste reduction targets. Importantly, the scenarios developed allow for a systematic examination of the benefits of improving municipal waste management systems on a global scale and identify what policy and technical measures can be taken in the waste sector towards a circular economy.

"Increased implementation of circular economy principles can make an important contribution to more sustainable development. The study shows that significant reductions in emissions can be achieved in this way. To achieve this, analyses at the level of the entire system are needed in addition to technical studies relating to individual products. For example, with the help of integrated assessment models, as in this case, but also on the basis of an overall consideration of society's use of materials and energy," concludes co-author Helmut Haberl, who works at BOKU.

Reference:

Gómez-Sanabria, A., Kiesewetter, G., Klimont, Z., Schoepp, W., Haberl, H. (2021). Potentials for future reductions of global GHG and air pollutants from circular waste management systems.

Nature Communications DOI: 10.1038/s41467-021-27624-7

www.nature.com/articles/s41467-021-27624-7

Contact:

Prof. Dr. Helmut Haberl
Institute for Social Ecology (SEC)
University of Natural Resources and Applied Life Sciences Vienna
Phone: +43 1 47654 - 73714
helmut.haberl(at)boku.ac.at