9-02: Conversion of municipal solid waste into bioenergy

The amount of municipal solid waste (MSW) is increasing in the developed part of the world. This is apparently an environmental problem but it also holds a large potential for energy production and recycling. However, the major challenge of utilizing MSW is the heterogeneous composition of plastics, biomass and metals.

Here we present a solid-liquid technology for separation of biomass from other waste components followed by possible gasification or fermentation. The philosophy behind this concept is sustainability, no pre-sorting of MSW, full recovery and improved usage of the different waste components. This technology is based on an initial thermal treatment of the entire MSW material which opens up cardboard based packaging and pulp & paper fractions and makes the other organic parts more accessible. Secondly an enzymatic liquefaction is initiated of the biomass fraction which turns this fraction into a pumpable slurry and ease the washing and sorting of non-biomass substances. The third and finishing step is the separation by simple filtration which may include washing for extracting the bound biomass and for cleaning recyclable-non-organics.

Different commercial enzymes have been screened for their effect on liquefaction of municipal waste after thermal treatment of the material.

The overall concept of this process will be shown as well as results obtained so fare from small batch experiments and a pilot plant capable of processing 100 kg/hr continuously. Also required characteristics of the slurry product in order to fulfil demanding properties of different energy systems affecting this project will be discussed.