A technology for various treatment steps of residual and mixed municipal waste
The mechanical-biological treatment of wastes (MBT) is an established treatment option in several countries in order to reduce the volume of mixed municipal solid waste to be landfilled by 70 %. At the same time a highly calorific fraction of so-called refused derived fuels (RDF) and of valuable material are recovered and biologically stabilised material by means of a composting process is generated that can be landfilled without problems.
The investment and treatment costs for the simple UTV system are considerably lower as in an enclosed MBT plant or in waste incineration. A pre-condition is that the simple system keeps the considerable emissions (especially odours) away. This is what the UTV system proved in several countries with highest standards.
The flexible treatment capacity makes sense as well, as following to tenders or over the year waste amounts to be treated can change considerably.
Possibility A: Biological drying prior to treatment
Depending on the amount of separately collected biowastes the mixed municipal solid wastes contain between 20% and 60% wet organic components sticking to other wastes – preferably plastics. Drying of this waste can be achieved via biological degradation by temperatures of up to 85° C and forced aeration under a membrane cover permeable to water vapour. The more dry the waste is the more easier a subsequent treatment enables a segregation into various fractions, especially in a high-calorific fraction (mostly plastics) and into recyclable valuable matter. The latter applies for typical process steps at the mechanical-biological treatment plants MBT.
Possibility B: Biological degradation step at the mechanical biological treatment MBT of residual wastes or mixed wastes
The practice in some countries is to pre-treat the wastes in a mechanical and biological step (MBT) as an alternative to waste incineration, in order to degrade the organics in the waste by means of composting so that the residue fulfils the stability and acceptance criteria for a sanitary landfilling. A cost-effective solution for this biological degradation is composting of waste with the GORE® COVER System, i.e. under membrane coverage with forced aeration.
Possibility C: Post composting of the organic portion as a stabilisation prior to landfilling
The biological degradation of organics in waste can be achieved in 2 steps. An intensive main decomposition in an enclosed high-tech MBT plant with aeration and exhaust gas treatment and followed by a forced aerated post composting with the GORE® COVER System.
This allows to meet the stabilisation degree necessary for landfilling in a cost-effective way. The post-composting process can be carried out with the GORE® COVER System without odour emissions which would molest residents. After a successful post-composting step the stabilised material is sent to the landfill and incorporated there.