A new study indicates that composting projects have greater potential to reduce greenhouse gases and contribute to sustainable development than landfill gas projects. However, only 1.8 per cent of projects in the UN's Clean Development Mechanism1 involve composting whereas 6.6 per cent are landfill gas projects.
The Clean Development Mechanism allows developed countries to reach their Kyoto emission reduction targets by investing in sustainable projects in the developing world. With the Kyoto Protocol due to expire in 2012, it is an opportune time to take stock of the strengths and weaknesses of the system to inform a post-Kyoto treaty.
The IPCC (Intergovernmental Panel on Climate Change) has identified waste as a key contributor to climate change. Strategies, such as the EU Landfill Directive2, are in place to address this issue but waste in developing countries is predicted to increase and by 2020 will contribute a 7 per cent increase in total global landfill gas emissions. Previous research has suggested composting may be a better option for waste disposal as waste in the developing world contains a high percentage of biodegradables and is inexpensive although labour intensive.
The study is the first to compare composting with alternative waste management projects and other sectors in the CDM. Over half of the projects registered with the CDM are renewable energy schemes, and one quarter of projects are on methane avoidance. Nine per cent of all CDM schemes concern waste management - just 1.8 per cent of these are composting projects. The research further divided composting projects into municipal solid waste composting (0.6 per cent) and agricultural waste composting (1.2 per cent).
To try and understand the reason for this under-representation of composting, the study examined the method used to calculate GHG emissions reductions. The calculation tool was originally developed for landfill gas projects and, as such, appears to discriminate against composting. This is because counting of emission reductions for landfill projects starts when the landfill is closed and covered, which is usually about 11 years after the project commences. At this point initial methane reductions are large which means that so too are the financial rewards.
For composting, emissions are reduced from the start of the project and when the counting commences, it does so at a slow rate, which means it receives comparatively less financial reward.
Currently the Gold Standard (created by the WWF) is the most well-known tool that guarantees sustainable development, but it only considers renewable energy and energy efficiency projects. To calculate the contribution of composting to sustainable development, the study used a method (MATA-CDM) which considers 12 sustainability criteria. This indicated that composting can compete with other best-in-class CDM projects. Besides household energy efficiency, composting of municipal waste has the highest sustainability score (0.50). Composting of agricultural left-overs has a lower score (0.33), which is in about the same range as the score for best in class wind (0.32) and landfill gas projects (0.31).
Composting has great potential for reducing GHGs and encouraging sustainable development, but is de-incentivised by the CDM calculation methods. This could be rectified by modifying the methodology for calculating emission reductions and remunerating composting projects for their contribution to sustainable development. To help to maximise the potential of composting the study identified a number of requirements, including the correct fermentation process, inclusion of stakeholders and ensuring job generation. It should be remembered, however, that it is not an option to revert to composting for landfill projects which involve retrofitting of existing closed landfills where no methane recovery is organised.