Anaerobic Digestion of Municipal Solid Waste
Anaerobic Digestion of Municipal Solid Waste (MSW) refers to either:
- the anaerobic digestion of “black bag or mixed waste” where no source separated or kerbside recycling is in-place. In which case the “Dry Anaerobic Digestion” process can be used to reduce the organic activity of the waste, and generate some useful biogas, before it is landfilled.
- the anaerobic digestion of the organic fraction of “source separated waste”, usually done in CSTR (Continuous Stirred-Tank Reactor) biogas plants.
Before the organic fraction of the waste can begin, the mixed waste requires the separation of the organic material (organic or biological fraction) from everything else.
What is a Mechanical Biological Treatment Plant (MBT)?
The Difference Between STWs MRFs and MBTS
Most people are able to grasp the concept of Waste Transfer Stations (WTS). The name says it all, as a WTS is simply where the small loads from the refuse trucks are made up into large “bulk” loads for cost effective transport to the landfill.
Using a WTS avoids having to transport the waste out to landfills over increasingly large distances.
It is worth pointing out that while an RCV is transporting waste, the waste collection operatives (bin) either sit in the cab and enjoy the ride, or need to wait for the RCV to return before resuming their bin collection round.
In the UK and Europe most WTSs have been extended to include sorting facilities for recycling, and are now called MRFs (Material Recycling Facilities).
But, there is little public knowledge of MBT.
The Difference Between a WTS a MRF and an MBT Plant
An MBT Plant is a WTS with not only added sorting equipment recycling for recycling, but also a biological treatment stage such as composting or anaerobic digestion.
The MBT is one of the waste management technologies which are being increasingly used by the local authority waste disposal contractors. By transferring the relatively small loads of waste in each Refuse Collection Vehicle (RCV) into much larger trucks, money can be saved.
MBT facilities are an extension of the task of a WTS. That means that there could be quite a lot of MBT facilities built, within the next 10 to 15 years.
“Many Mechanical Biological Treatment Plants are being wee built in the UK during the period 2000 – 2010”.
Also, here are quite a number in the EU states already, and the Germans and the Austrians are the leaders in introducing them.
In Germany there are about 50 MBT plants, which were built and operating (January 2008), and clearly the local people have no concerns about them, or at least, very few, objections.
MBT Plants are designed for maximum recycling, and usually include a composting and/or an Anaerobic Digestion stage.
They also are intended to make the quality of the much reduced quantity of waste, which is the remaining fraction of municipal solid waste (MSW) which cannot be re-used or recycled much less damaging when the residual quantity eventually arrives at the landfill.
An alternative to an MBT Plant is an incinerator.
MBT plants are much more popular with the general public than incinerators.
Green pressure groups argue that incinerators, once built, reduce the incentive for the staff to recycle. The more they burn in an incinerator the more electric power they can generate and the bigger the income to pay for the Incinerator.
In contrast to that, there is no question that a MRF or an MBT plant operator would not absolutely maximise re-use and recycling of the incoming materials. After all, the income for such plants comes from the sale of the recycled materials.
Does the Presence of an Incinerator Tend to Reduce Local Recycling?
The author of this article is not convinced that such an argument against incinerators, is a real one.
He considers it likely that, that incinerator operators re-use and recycle to the maximum in accordance with the requirements placed upon them. That means that if the community which the incinerator serves takes measures to ensure that contractually the incinerator operator must recycle to a set level, and checks are in-place. There is no problem. However, the local community/ Council Officers do need to inspect the incinerator records regularly. The intention must be to ensure that the recycling targets are being met the incinerator manager.
However, the public and environmental pressure groups don’t always see it that way.
In fairness to those people that run incinerators, though. Once built, they do need to pay-back their initial investment cost. Recycling rate targets are continuously being raised.
This can lead to older incinerators, having been designed for lower recycling rates than currently required, lacking the equipment to comply with the newer higher recycling rates. In such cases, those plants tend to act against raising recycling rates, until they reach end-of-life and are refurbished to cope with the new recycling rate requirements.
How Does a Biogas Plant Work?
Watch our video below to find out!