Organic waste - treatment options, opportunities and barriers
There is approximately 14 million tonnes of biodegradable organic waste produced by households in the UK every year which must be treated or disposed of. The EC Directive on Landfill (1999/31IEC), is likely to lead to an increase in compo sting and anaerobic digestion as methods to treat the waste stream diverted from landfill. Householders play an important role in separating their waste, which, if not performed efficiently can lead to contamination of the organic waste stream, and hence the compost product. A survey is used to determine the attitude and behaviour of householders to waste issues. It was found that residents in the less affluent area were less likely to home compost and had a less favourable attitude towards environmental activities than residents in the affluent area. A comparison of compost from centralised composting schemes treating different organic waste streams found that compost derived from household waste was of a slightly poorer quality than that obtained from gardens/parks waste. As more waste is recycled as compost, it is becoming increasingly important to find alternative uses for compost. Leachability data are used to determine the environmental availability of Cd, Cu, Pb, and Zn contained in natural compost. Batch sorption data are used to determine uptake of additional Cd, Cu, Pb, and Zn by compost and assess its potential use in remediation work, as an alternative to natural materials such as peat. The relative binding of these additional metals to compost is found to be in the order Pb>Cu≈Cd>Zn. The sorption of metals on compost takes place, at least in part, by exchange of calcium bound to the compost and there is evidence that the sorption occurs in both the humic and non-humic sites in the compost. The use of compost to bind metals in remediation work is discussed.