Workers stand next to a large metal tank.
An anaerobic digester located at the City of Tshwane’s Zeekoegat Wastewater Treatment Plant.

The Multiple Benefits of Turning Waste to Energy

By Peter Nash

Landfills and wastewater treatment plants generate methane, a potent greenhouse gas (GHG), from decomposing organic waste and wastewater treatment processes, respectively. What if there were ways to reduce GHG emissions while simultaneously creating renewable energy? And what if there were additional benefits beyond reducing emissions and creating energy?

In South Africa, provincial and municipal governments are supporting the national government’s ambitious GHG emissions reduction targets in a variety of ways, including recovering methane from wastewater treatment processes, and by generating renewable energy through diverting organic waste from landfills. While the benefits of reducing emissions and generating renewable energy are valuable on their own, a variety of other benefits can be realized from these types of low emissions development (LED) projects. To highlight the multiple benefits of turning waste to energy, let’s briefly explore what two South Africa Low Emissions Development Program (SA-LED) municipal partners are pursuing in the areas of combined heat and power (CHP) and diverting waste from landfills.

Combined Heat and Power

The city of Tshwane in Gauteng Province engaged SA-LED to support the development of a CHP plant at their Zeekoegat wastewater treatment plant. SA-LED conducted an infrastructure and operational audit of the plant, assisting with the detailed design of the CHP system for Zeekoegat. The CHP plant will take methane generated from anaerobic digestion to meet all or a portion of the overall wastewater treatment plant’s energy needs. Not only can the methane be combusted to generate electricity in a turbine, but residual heat can be recovered for use at the plant, such as heating the digesters that break down waste.

Combined heat and power plant in Tshwane, South Africa will have the capacity to generate 0.4 MW and could reduce over 3,000 metric tons of CO2e per year.

CHP therefore provides an efficient and renewable way to recover the maximum energy value from the methane produced at the plants, which would otherwise be vented or flared. Moreover, CHP can offer additional benefits of decreased electricity costs (plants in South Africa account for 20 percent or more of municipal energy consumption) and improved reliability of the plants through minimizing the impacts of power outages on plant operation, which is particularly prevalent in the South African context.

Image

Large covered sludge fields with grass in the foreground.
Sludge drying beds located at the City of Tshwane’s Zeekoegat Wastewater Treatment Plant.

Diverting Organic Waste from Landfills

The Garden Route District Municipality in the Western Cape Province faces challenges with waste management, largely due to the district landfill exceeding capacity. The municipality also had large amounts of organic waste that could be used for LED projects but was not aware of the exact organic waste streams, their volumes or flows, or what to do with each stream. SA-LED supported the municipality by conducting a waste characterization study that identified six organic waste streams and their respective volumes and sources. Then SA-LED developed a waste management decision-making tool that determines which waste management technologies and processes can be applied to manage and/or divert the waste streams away from landfill. With the tool, the municipality now has the ability to make informed decisions on how to assess proposals and determine potential technologies to apply to each waste stream, including (but not limited to) waste-to-energy, composting, and anaerobic digestion. For each alternative practice, the tool also calculates additional benefits, including avoided landfill waste, GHG emissions reductions, energy use, and jobs supported.

The municipality has plans in place to construct a new composting facility. If approximately 32,000 metric tons of organic garden waste per month were to be diverted to the facility, the lifespan of the municipality’s landfill could be extended by 10 years.

Composting organic waste could reduce GHG emissions by 11,500 metric tons of CO2e per year and save the municipality $1.7 million annually.

Additionally, through the waste characterization analysis, SA-LED identified slaughterhouse waste as the most problematic food waste type to manage due to its hazardous nature. One solution to manage the potential negative impacts is anaerobic digestion, which generates biogas that can be used to produce heat or electricity, as well as a by-product that can be used as fertilizer. If slaughterhouse waste is diverted from landfills into anaerobic digestors, GHG emissions would be reduced through methane capture and renewable biogas energy generation, resulting in an estimated reduction in GHG emissions of 5,700 metric tons of CO2e per year. The construction and maintenance of the anaerobic digester facility would also create 53 new local jobs. Diverting this waste would also extend the landfill’s lifespan by three years with 9,700 metric tons of slaughterhouse waste diverted annually. Finally, 290 metric tons of fertilizer would be created annually, providing an alternative to chemical fertilizers.

As these two examples demonstrate, a variety of benefits can be realized from turning waste into energy projects. Benefits such as reduced energy consumption, cost savings, improved reliability, extending municipal infrastructure lifespans, and job creation can help policymakers promote and justify LED projects, encourage investment or budget allocation for LED projects, and aid in the expansion of existing LED projects.

To learn more about turning waste to energy and the multiple benefits of LED projects and to access a variety of LED that SA-LED produced, please visit the SA-LED Program page on Climatelinks.

Country
South Africa
Sectors
Energy
Strategic Objective
Mitigation
Topics
Adaptation, Carbon, Emissions, Low Emission Development, Climate Change, Conflict and Governance, Clean Energy, Infrastructure, Mitigation, Urban
Region
Africa

Peter Nash

Peter Nash is an international development leadership and management specialist with more than 12 years of experience, including implementing and providing administrative, financial, and operations support for USAID-funded programs in east and southern Africa. He is currently a director in Chemonics’ East and Southern Africa Division. His technical expertise includes natural resource management, climate change adaptation and mitigation, youth development, and environmental education. Mr. Nash holds a M.S. from Colorado State University in human dimensions of natural resources and a B.A. from Connecticut College in environmental studies and anthropology.

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