Landfill Directive targets “more easily delivered” with MBT

That is the finding of a landmark study on mechanical biological treatment (MBT), published by the SITA Environmental Trust today. The 250,000 study has been funded through the Landfill Tax Credit Scheme and is being made freely available to the public.

”Despite the claims from some policymakers and NGOs that MBT can be part of zero waste, we do not agree. MBT will produce a certain amount of waste that cannot be recycled or used.“
– Joe Schwager, Juniper

In a largely positive report on MBT technologies, consultants Juniper found that systems have the potential to achieve diversion rates of up to 95%”. But, the study warned that if local authorities opt for the wrong system, diversion rates could be as low as 14%.

The actual proportion of dry recyclables recovered through was “modest”, the Juniper study said, typically between 3% and 15%. But, the way composting contributes to recycling rates meant “reported recycling rates” could be “as high as 85%”.

Process
MBT – mechanical biological treatment – is a family of technologies that partially process mixed household waste by mechanically removing some materials and by biologically treating others so that the residual fraction is smaller, more stable and available for a number of possible uses.

MBT is not a single process, but can vary considerably with the 15-month Juniper study looking at the technologies offered by 27 different companies worldwide, including the appraisal of 30 existing plants in nine countries.

Joe Schwager, managing director of Juniper, advised local authorities not to focus too much with what a potential MBT process may involve, but instead attention should be centred on what the end products and residues are. “It really doesn't matter what is in the black box,” he said, “it just matters what comes out of it.”

End uses
Among the process, the Juniper study identified 24 possible end uses, but four main MBT routes. MBT processes could be combinations of these four options:

• Stabilising material to send it to landfill
• Use of material as compost
• Use of material as a solid fuel
• Focus on producing a biogas fuel

Mr Schwager said there was “no overall winner”, but that the report identified the best kinds of technologies for certain situations. “Some types of MBT are more suitable for a different type of project than another. We think that it is likely that we could recommend a different shortlist for each project but it is very much 'horses for courses'”.

Contrary to popular opinion in the UK, the Juniper study found that most MBT plants in Europe stabilise material for landfill, with the second most popular route that of producing biogas. Producing a refuse-derived fuel is the least popular of the four options, the study found.

The report said that unless government policy changes, the take-up of MBT residues as a replacement for fossil fuels in power stations – and the use of residues as agricultural compost – will be “very limited”.

Zero waste
Mr Schwager warned that the claims of some campaigners that MBT was the answer for reaching the “zero waste” goal were not borne out by the study. Mr Schwager said: “Despite the claims from some policymakers and NGOs that MBT can be part of zero waste, we do not agree. MBT will produce a certain amount of waste that cannot be recycled or used.

“That term is not appropriate for this or any other waste technology,” he added.

The Juniper study suggests that there could be less need for large numbers of energy-from-waste plants than had been previously thought, but suggests MBT plants used in conjunction with thermal processing “could have the loest gate fees and be less risky to implement”.

Proven
Dr Egan Archer, technology consultant at Juniper, said there were 80 operating plants in the world, currently processing about 8.5 million tonnes a year of material.

Spain has the largest plants in the world, where MBT is partly used to stave off the desertification of the country, with the largest plant processing 480,000 tonnes of waste each year. Most plants operating in the world process 100,000 tonnes or less each year, with the smallest in the Juniper study being a 20,000 tonnes capacity.

MBT is “well established and proven” on the continent, Dr Archer said, and the technology much more proven than other technologies such as pyrolysis and gasification.

Dr Archer warned councils not to take the claims of technology companies at face value, and said that headline data “can be misleading”. He explained that supplier experience varied widely and that no single supplier had experience with all forms of MBT.

Dr Archer said: “Some companies are partners in certain plants, and several companies claim the same plant as their reference plant, but they may have no experience in building a whole plant.”

The full report, Mechanical Biological Treatment: A Guide for Decision Makers: Processes, Policies and Markets, is available on the SITA Environmental Trust website.