Proceedings

Recycling organic wastes to land is seen as a beneficial and sustainable use of such wastes as it improves soil structure, fertilizes the soil, conserves natural resources (N, P, K), and sequestrates organic carbon into soils that may help to off-set global warming. The requirement to divert biodegradable organic matter from landfills means that potentially much more organic waste may be recycled to land. The current trend is however to prebiologically treat organic waste prior to recycling and this has some benefits such as reduction in odour producing potential and destruction of pathogens. Such processes however also lead to a more rapid return of the carbon to atmosphere as CO2 and may consume energy for the biological treatment, and produce waste streams that require additional treatment. All these additional steps will result in more CO2 emissions, and possibly emissions of other greenhouse gases such as nitrous oxide, and the loss of potentially valuable nutrients. Therefore the question is raised: is it better to prebiologically treat organic wastes destined for recycling to land? This paper highlights some of the issues that may need to be considered in order to provide an answer.

KEY WORDS Anaerobic digestion, biodegradable, carbon, compost, landfill diversion, methane, nitrous oxide, soil, waste