Urban Waste Disposal

Improved access to municipal waste services in a favela of Brazil

Strategies for waste reduction, separation, processing, management and recycling and reuse are feasible, low-cost alternatives to the open incineration of solid waste, which is common now in developing cities. Where incineration is unavoidable, then combustion technologies with strict emissions controls are critical.

Improved collection, management and disposal of urban waste is one important strategy that can yield multiple improvements in both climate and health. Using anaerobic digestion, methane emissions can be captured from sewage, livestock manure, and landfill solid waste, and used as biogas or bio-methane, a fuel for cooking, heating or power needs. A

Anaerobic biosolid digestion systems can produce a gas composed of 55% to 70% methane, which is typically much cleaner than biomass combustion, although not as low-emissions as natural gas.

As a renewable fuel, methane capture and use, however, has many other health and environment advantages. The process reduces methane emissions to the atmosphere that contribute to ozone, which are a factor in chronic respiratory illnesses, as well as a contributor to climate change. Finally if biogas replaces biomass or coal combustion in household cooking or heating, then household and outdoor air pollution will also be significantly reduced.

Millions of rural households in China, and thousands in Nepal, already generate biogas cooking fuel from animal waste in small, simple digesters. Insofar as these also process household sewage waste, biogas production also requires a hook-up to an improved latrine, which has a sanitation benefit as well.

In larger, industrialized plants that exist at urban level, recovery of over 90% of methane gas can be achieved with established technologies. Improved urban wastewater treatment systems can also provide a source of methane capture and purification, and the resulting fuels may be used as a clean source of urban power generation as well as for households.

The UNEP-affiliated Climate and Clean Air Coalition, in which WHO is a leading member, has launched a municipal solid waste initiative which fosters technical training and awareness-building to assist cities around the world in mitigating methane emissions from municipal solid waste landfills.

Methane capture in a biogas system at the Gramacho
landfill in Rio de Janeiro, Brazil

UN Foundation

Sustainable waste management activities can serve as a catalyst for local economic development as well. For instance, a joint U.S.-Brazil initiative, created in collaboration with municipal authorities, and with the support of financing from the UNFCCC’s Clean Development Mechanism, created a methane capture system in Rio de Janeiro’s Gramacho landfill. This biogas project improved waste enclosure and drainage, a sanitation benefit for the city, as well as introducing methane flaring and connection to purification for use as an income and energy source. The project is anticipated to produce 90 million normal cubic metres (Nm3)of biogas on average over 20 years.