Experts back mechanical-biological treatment

Wider use of mechanical-biological treatment (MBT) of household waste could contribute significantly to meeting environmental goals in many countries, according to a major review of the technology. The study was part-funded by European sustainable resource use association Assurre and published on Tuesday.

Claimed as the biggest ever review of MBT, the study examines in detail 27 different kinds of MBT plants in nine countries. The technology holds considerable potential for countries under pressure to divert biodegradable waste away from landfills, it concludes. And more so in countries like the UK and Ireland where there is strong public hostility to waste incineration.

MBT could be even more attractive in the EU's ten new member states, the report concludes. Here, not only is almost all waste still going to landfill, but household waste recycling is also undeveloped. MBT plants can tackle both problems simultaneously, it states.

The study classifies MBT as a novel technology, but one in which considerable experience has been built up over the past decade. After first emerging in Germany and Austria it is now most widely used in Spain followed by Italy and Germany, and is present in another dozen countries.

Key to understanding MBT is the fact that it is not one technique but rather a family. Depending on the policy and commercial objectives, MBT plants can be designed in many different ways. Most plants in Spain are optimised to produce a low-grade compost used to improve arid land, for exampe. Two large Dutch plants produce biogas.

In Italy and Germany, plants have generally been built to stabilise and reduce waste, which is then landfilled. This helps reduce dumping of biodegradable waste, as required by the EU's 1999 landfill directive, without resorting to incineration. Some plants turn stabilised output into refuse derived fuel (RDF) instead of landfilling it.

MBT faces challenges, the report also explains, including many regulatory uncertainties. An EU biowaste directive with standards for MBT-produced composts was promised and then withdrawn. An EU soil strategy establishing guiding principles for use on land of waste-derived materials is still awaited.

An EU best available techniques reference document (bref) for waste treatment that should enable regulators to decide whether MBT plants comply with the 1996 IPPC directive is still not finished, the report goes on. The regulatory status of biogas combustion in gas engines is unclear. And standards for solid recovered fuels are not likely to be finalised until 2008.

Republished with permission of Environment Daily



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