The SWEET Tool Sparks Change in Cities Around the World by Measuring, Monitoring, and Mitigating Waste Emissions

From devastating seasonal flooding in Ghana’s capital of Accra, to a plague-like epidemic in Surat, India in 1994, to a landslide in the Philippines Quezon City in 2000, uncontrolled and unmanaged municipal solid waste can be deadly. Beyond the clogged drains and disease breeding grounds, the trash that cities produce is a significant source of short-lived climate pollutants (particularly methane and black carbon) which have devastating impacts on climate change and clean air. In fact, it's estimated that the waste sector is responsible for over 12 percent of global methane emissions, one of the most significant contributors to climate change. At least a third of the world’s waste is mismanaged through open dumping or burning. The problem is also getting worse: by 2050, annual waste generation is expected to increase by 70 percent, up from over 2 billion tonnes in 2016. 

Given how cities are central to global waste production, there is also a huge opportunity for them to address the problem. It’s hard, however, because you can’t manage what you can’t measure.  Understanding exactly where waste sector emissions come from is tricky— from open dumps and landfills, to open burning, to composting facilities, to incineration facilities, and waste handling equipment like bulldozers and garbage pick-up trucks, each city has a variety of sources of emissions all along the waste management chain.

To bridge this gap, the United States’ Environmental Protection Agency (US EPA) in support of the Climate and Clean Air Coalition’s (CCAC) Municipal Solid Waste Initiative developed a tool in 2017 called the Solid Waste Emissions Estimation Tool, or SWEET. It’s Excel-based and municipalities can download it from the CCAC Waste Initiative’s Knowledge Platform. Cities can use SWEET to get a baseline measurement of their waste emissions and monitor them over time. They can also measure the ways that different interventions would impact emissions levels over time — how would installation of a biogas collection system at a landfill affect emissions? How much black carbon could be averted if they upgraded their waste collection fleet?

If a city has overall emissions reductions goals, SWEET helps them better understand how investments in waste management in particular will contribute to those goals, which helps cities prioritize interventions and make financing decisions. The tool can also help the city see and how their emissions compare to other cities.

“One of the things the tool does best is help communicate to people how significant emissions from landfills are relative to other emissions sources in the waste sector,” said Joe Donahue, Senior Associate, Abt Associates. “Landfill emissions just dwarf everything else and I think until this tool existed, a lot of cities didn’t understand that.”

Unregulated dumpsites, in particular, are a huge problem for methane and black carbon emissions. According to the International Solid Waste Association, dumpsites receive 40 percent of the world’s waste and the globe’s 50 biggest dumpsites affect the daily lives of 64 million people. In low-income countries, just 36 percent of the population has a trash collection service.

A major objective for the tool was that it would help cities connect the dots between the waste sector, climate, clean air, and other development indicators. Waste can seem like an intractable problem and SWEET can help cities recognize that intervening in the waste sector is a lot easier than it seems— and that the multiple benefits can be big.

“Once we help them connect the dots between food security, logistics, transport, job generation, environmental impact, they realize that with relatively simple actions and decisions they can mitigate emissions,” said Gabriela Otero, a Technical Coordinator at ABRELPE who has helped multiple cities in Brazil start using SWEET. 

Ms. Otero and her team started running the SWEET tool in 2017 in the southern city of Curitiba and then soon after in Sao Paulo, the most populous city in Brazil with over 12 million people. 

“When you see how big the numbers are for potential emissions avoided if they make the right decisions it is really attractive,” said Otero. “The SWEET tool is a very good technical and political commitment tool.”

Already, the mayor of Sao Paulo has incorporated the emissions mitigations calculated using SWEET’s tool into the city’s strategic goals, citing CCAC’s Waste Initiative as the reference point for their goal of reducing and diverting solid waste from landfills. The tool showed that diverting organic waste from landfills, including by composting it, can lead to emissions mitigation which helped motivate an increase in the number of decentralized composting facilities. 

Now, their team is running the SWEET Tool in Rio de Janeiro to understand the current waste emissions of the city, as well as the potential emission reductions from proposed interventions. They’re also gearing up to use it in Manaus in the heart of the Amazon.

Like many countries around the world, Brazil struggles with financing solid waste, Otero says that of the country’s 5,570 municipalities, only 15 percent charge waste fees to help fund the sector. SWEET’s measurements are already helping cities access climate finance, equipping them with solid data that offers proof of what they can achieve with funding.

“The project we developed under the CCAC Waste Initiative is being presented to international development banks because the potential for mitigation is really, really substantial,” says Otero. “This is part of why municipalities are excited about the SWEET tool and also about joining the CCAC, they want to transition to an environmentally friendly waste management system and also it can help them access climate funds and environmental funds.”

Brazil isn’t the only country leveraging SWEET's possibilities. In fact, the tool has been so popular that the development team regularly hears from cities in countries they’ve never directly engaged with. Today, it's been used in 44 cities across 31 different countries.

“I’ve been really just continually pleasantly surprised by its adaptation,” said Tom Frankiewicz, Program Manager, U.S. EPA,. “It’s been interesting to see how people are using it and how quickly it’s been disseminated.”

From the World Health Organization using it to model public health impacts in Accra, Ghana, to groups trying to use it to better understand the emissions impacts of plastics going into the ocean, Frankiewicz says the tool has taken on a whole other life in an exciting way. The International Solid Waste Association also used the tool for its #CloseDumpsites Campaign to document the effects of closing dumpsites in Brasilia, Vienna and Tel Aviv. The team of developers also receive regular emails from PhD students around the world looking to use the tool in their research. From Madagascar to Nepal, and Ecuador to Mongolia the tool has helped organizations better understand their waste management options.

India is another country where the SWEET tool has been widely deployed. 

As part of technical assistance provided by CCAC, SWEET was used for the East Delhi Municipal Corporation and Coimbatore City Corporation to help them develop work plans to improve waste management and mitigate SLCPs. The city used the tool to create a baseline for their  waste emissions and came up with alternate strategies to reduce them. In East Delhi this led the city to take decisions like not increasing the capacity of existing incineration plant (waste to electricity), decentralized composting facilities and bio-methanation plants that supply electricity to the grid. There is also an anaerobic digestion project for handling cow dung from the municipal area.

Likewise, the Energy and Resources Institute (TERI) used SWEET in Varanasi and Panaji, as part of a waste NAMA project (implemented with GIZ India) to evaluate baseline emissions and estimate the emissions that could be reduced through different project activities such as bio-methanation, recycling and composting.

“More and more cities are joining the CCAC and I believe models like SWEET are part of the reason, so that they can understand what their emissions trajectories will be and how they can reduce their emissions,” said Sourabh Manuja, Fellow, TERI.

Manuja adds that the SWEET tool is part of the curriculum of a course he teaches on Waste Management at the Indian Institute of Forest Management in Bhopal and that it was a part of a training session he took on waste management and climate change.

SWEET isn’t yet being used for national policy but Manuja hopes that can be the next step.

In Naucalpan de Juárez, Mexico, the SWEET tool was used to analyse the environmental benefits of an anaerobic digester to convert organic waste into biogas to generate electricity. The city used the emissions reductions analysis as technical justification to secure project funding, including a grant from Mexico’s National Bank for Public Works and Services to cover up to half of the project. 

Like any tool, SWEET’s utility depends a lot on the data that’s put into it.  It can be hard for cities to collect complete information about their waste management, particularly in places with unregulated activities like open burning. Luckily, collecting better waste data is an aim of the Sustainable Development Goals which is helping nudge cities towards building a more concrete information base about their waste. Soon enough, this growing database paired with tools like SWEET will help transform municipal waste around the world.

Watch the video below to learn more about SWEET.