Methane is generated from solid waste and wastewater through anaerobic decomposition.
Together, solid waste and wastewater disposal and treatment represent about
20 per cent of human-induced methane emissions. Emissions are expected to grow
in the future, with the largest increases coming from developing countries.
Methane emissions can be reduced in many ways, including reducing waste generation
(source reduction), diverting waste away from disposal sites (i.e., through
composting, recycling, or incineration), recovering methane generated from the
waste, or ensuring that waste does not decompose in an anaerobic environment.
In general, any technique or technology that reduces methane generation or converts
methane into carbon dioxide through combustion will reduce greenhouse gases
(GHGs). The most effective mitigation approaches are those that either reduce
overall methane generation (because methane collection efficiencies rarely approach
100%) or ensure that the combusted methane is substituted for fossil-based energy.
Extensive technology transfer aimed at improving waste management is underway
both within and between countries, although most activities have been, and will
likely continue to be, domestic in nature. In many regions, large investments
are still required to provide adequate waste management services. In the past,
the climate-related impacts of waste management choices were not routinely considered.
Mitigation technologies can be readily deployed in this sector, however, and
provide benefits beyond the reduction of GHG emissions, such as reduced landfill
space requirements or additional energy generation through methane recovery.
Technology transfer in the waste management sector occurs predominately along
government driven pathways, with several levels of government (from the national
to the municipal level), participating. Key government priorities are establishing
appropriate policy/regulatory frameworks, supporting the expansion of private
sector participation, participating in technical assistance and capacity building
activities, particularly with community groups, and in some cases providing
incentives to catalyze desirable actions. This is discussed in more detail in
Historically, the private sector (including both domestic and multinational
companies, as well as more informal local enterprises) and community-based organisations
have been somewhat limited participants in government-driven technology transfer.
The private sector has an increasingly important role, however, because meeting
future waste management needs depends on expanded private investment. Private
sector driven pathways are already used routinely for some types of investments
(such as methane recovery at landfills), and efforts are underway to expand
private sector participation across the full range of waste management services
and technologies. The involvement of community organisations is also increasing
as the link between community support and project sustainability has become
clear. Soliciting local input and providing local training are two ways of ensuring
sustainability. In many areas, locally developed and implemented projects are
also being used to quickly address serious local concerns.
This review of the waste management sector reveals several key findings. This
sector can contribute to greenhouse gas mitigation in ways that are economically
viable and meet many social priorities. Already, extensive technology transfer
is underway, and it will continue due to the continuing need to provide and
improve waste management services for the world's population. In the past, the
government driven pathway has dominated this sector, and it will likely dominate
in the future as well. However, additional levels of government are becoming
involved, as national government agencies devolve responsibilities for waste
management to regional and municipal agencies. Private sector and community
driven pathways are also becoming more important in this sector. Regardless
of the pathway, it is important that projects emphasise the deployment of locally
appropriate technologies, and minimise the development of conventional large,
integrated waste management systems (with their attendant financial, institutional
and technical requirements) in situations where lower cost, simpler alternative
waste management technologies can be used.