Cancún, Mexico – The waste management sector is contributing 3-5 per cent of global man-made greenhouse gas (GHG) emissions, equal to around the current emissions from international aviation and shipping, according to some estimates.
But the report says the waste sector is in a strong position to move from being an emissions source to being a major emissions saver, in part by harvesting the methane from rubbish tips for fuel and electricity generation. In doing so, the sector can play a role in bridging the gap between where emissions need to be in 2020 and where emissions are heading under the various pledges associated with the 2009 Copenhagen Accord.
According to the recent Emissions Gap Report, presented in advance of the UN Climate Change Conference in Cancun by United Nations Environment Programme (UNEP) and researchers from 25 modelling centres, a best-case scenario would see emissions fall to around 49 gigatonnes (Gt) of C02 equivalent, if the Copenhagen pledges are fully implemented.
Scientists estimate that emissions need to be as low as 44 Gt in 10 years’ time to stand a good chance of keeping a 21st century temperature rise to under 2°C. Accelerated action on C02 emissions will be key to bridging this 5 Gt gap. But this could be assisted by greater action on a range of non-C02 pollutants ranging from black carbon and nitrogen compounds to methane.
“Every avenue, every opportunity and every option for cutting greenhouse gases needs to be brought into play if the world is to combat dangerous climate change and set the stage for a transition to a low-carbon, resource-efficient Green Economy urgently needed in the 21st century,” said Achim Steiner, UNEP’s Executive Director and Under Secretary General of the UN.
“The waste sector is already acting to minimize the impacts of potentially potent greenhouse gases like methane, but this is often done on a country-by-country basis. The time is ripe to scale up and deliver a far more coordinated and global response, especially in respect to developing economies. This offers multiple benefits ranging from curbing greenhouse gas emissions to generating new green jobs and increased access to energy from waste-into-electricity projects,” he added.
The report, “Waste and Climate Change: Global Trends and Strategy Framework”, was prepared by the UNEP’s International Environmental Technology Centre, based in Japan. The authors examine the contribution the waste sector can make in the fight against climate change and suggest a strategy for increasing this contribution.
The report lists three main areas in which GHG savings can be made in the waste sector:
- Reducing the amount of primary materials used in manufacturing through waste avoidance and material recovery through recycling (avoiding the GHG emissions from the energy used to extract or produce the primary materials);
- Producing energy from waste to replace energy from fossil fuels;
- Storing carbon in landfills and through the application of compost to soils.
But the study also underlines that much work remains to fully estimate the potential emissions contribution – and thus, possible emissions savings – from the waste sector because in many countries, data can be patchy and methods of calculating waste-related pollution vary between nations.
Indeed the report notes that levels of uncertainty can be as high as 10-30 per cent for developed countries (with good data sets) to more than 60 per cent for developing countries that do not have annual data.
Methane emissions from landfills are generally considered to represent the biggest impact on the climate from the waste sector, followed by incineration of waste. Methane is generated in landfills when microbes form and begin to break down organic matter, such as food, paper, wood or garden trimmings.
A roughly even mix of carbon dioxide and methane gas forms during the decomposition process, but the practice in some locations of burying or covering waste can result in a greater proportion of methane being produced. When that methane escapes into the atmosphere, it is thought to have a global warming potential 25 times that of carbon dioxide over 100 years.
Landfills that have gas recovery systems in place capture the methane and convert it into fuel and compost. Capture rates vary from landfill to landfill (because they depend on the mix of the materials dumped in them), but estimates from managed landfills in developed countries put capture rates at 50-80 per cent.
One study quoted in the report suggests emissions savings of 132-185 kg CO2 equivalent per tonne of wet, mixed municipal solid waste input stored in well-managed, European landfills. Another study suggests that simply by diverting food, garden and paper waste to composting or recycling stations, thereby reducing the amount of organic matter in landfills, emissions could be cut by 250kg CO2 equivalent per tonne of municipal solid waste.
For example, Germany, between 1990 and 2005, gradually banned untreated organic waste in landfills. By 2012, it is expected that this will have avoided 28.4 million tonnes of CO2-equivalent of methane emissions.
The report estimates that in many developing countries, the level of organic waste (and thus, a potential source of methane emissions) is around 50 per cent and could, in a rapidly developing country such as China, represent more than half of the waste stream up to and beyond 2030 if no action is taken.
The report notes that handling of greenhouse gases in the waste sector needs to be considered in the light of other environmental, social and economic implications of waste management strategies, which will differ from location to location.
Although average annual per capita waste generation in developing countries is estimated at 10-20 per cent of that of developed countries, this figure is rising in response to economic and population growth. One of the key challenges is to de-couple waste production from economic growth.
