Continuing with the theme of Recycling Week, here is a brief introduction to Mechanical Biological Treatment of domestic waste.
What is Mechanical Biological Treatment (MBT)?
It is a method for sorting through domestic waste and separating it into materials that can be recycled such as glass, metals and plastics or organic materials that will decompose, such as food waste.
What are the benefits of it?
It avoids the need for us to put our waste in to separate bins and the local authority needs only one type of refuse vehicle for all waste. Communities minister Eric Pickles last year urged all local authorities in England to consider adopting this type of waste treatment so that they can re-instate weekly refuse collections.
Sounds good, but can the same recycling rates be achieved?
Not really. It can recover some more metals than would normally be collected through kerbside recycling schemes, e.g. metals other than cans but the majority of recyclable material that is recovered is of an inferior quality to that collected separately at kerbside. This means that it is of lower value than other materials on the market and it is often processed overseas.
Will there not be a big benefit from making all that compost rather than putting the waste in landfill?
Again, no. Compost made from mixed refuse does not meet the standards required for agricultural or horticultural use (PAS100) as there are too many contaminants. To meet these standards, organic waste must be collected separately, such as garden waste which can be readily composted and used as a growing media. Some organic wastes, especially meat or cooked food waste should be composted at higher temperatures to ensure pathogens are killed off. The composting process used as part of MBT is only effective in reducing the volume of material going into the landfill.
Is there any point to MBT then?
It is no substitute for a proper recycling scheme but it does have the benefit of reducing the volume of residual wastes going to landfill and the composting process makes these wastes less active hence emitting less methane once in the land fill. Reducing the volume subsequently increases the life of existing land fill operations, rather than opening new land fill sites.
In conclusion, it is lazy, inefficient and, as the sole means of treating waste, is no substitute for separate recycling streams at source.
More information from Friends of the Earth: http://www.foe.co.uk/resource/briefings/mchnical_biolo_treatmnt.pdf