Support for AD
A recent report prepared for the Waste Resources & Action Programme (WRAP) by Eunomia, the independent consulting organisation, shows that there can be real cost and environmental gains from the separate collection of garden and food waste and that Anaerobic Digestion is the optimum method of dealing with food waste.
The report summary states: “If the system chosen for bio-waste collection and treatment is separate collection of food waste coupled to Anaerobic Digestion, the environmental performance of the system is likely to be the best compared to all the other systems”.
It goes on to summarise its findings as follows:
The following points are clear:
- Both Anaerobic Digestion and in-vessel composting are suitable for processing food waste with a view to generating a saleable product
- Anaerobic Digestion is more favourable from an environmental perspective, primarily because the process produces methane which can be used to generate energy.
...where collection and treatment systems are well integrated, consideration should be given to the possibility of collecting food waste separately for digestion. If these collection systems can be coupled to AD processes, it should prove possible to generate both energy, as electricity or heat, and quality products for use in various applications.
There is likely to be a considerable environmental dividend from a shift in this direction. If the 5.5 million tonnes of UK municipal food waste were targeted for separate collection, then the total quantity of electricity generated could be of the order 477-761 GWh per annum if the material was digested. This is equivalent to the electricity used between 103,000 - 164,000 households, or 16-26% of the energy generated by wind power in the UK in 2005.
Composting the same amount of material would utilise energy in the process. The net position in respect of greenhouse gases is likely to be such that routing the material through AD rather than composting will improve the position in respect of greenhouse gases to the tune of more than 0.22 - 0.35 million tonnesCO2 equivalent. If the same amount of material had been landfilled, savings increase to 1.6 - 3.6 million tonnesCO2 equivalent, depending upon the performance of both the landfill and the digester.
Some countries are using approaches to optimise collection systems, others are moving more towards digestion as an approach to bio-waste treatment. Few are doing both.
This report shows that the UK can learn from this experience and implement cost effective systems for the collection and management of bio-wastes, which reduce greenhouse gas emissions and bring real environmental benefits.
Click here to view the WRAP report
