Solid waste management is becoming a cumbersome task for the city corporations and sewerage authorities in Bangladesh as the generation is increasing day by day. Current practice of solid waste processing is inefficient with some uncoordinated attempts by a few to recycle a small fraction followed by dumping at landfill sites. The process is responsible for polluting soil and groundwater with toxins, contributing to the climate change by releasing green-house gases and causing health problems to living beings.
There are several routes for harnessing electricity from solid waste. A few of them (combustion, pyrolysis and gasification) require drying of high moisture waste material and hence have low efficiency. Biological treatment (AD) requires longer retention time and have high land requirements. As a result, the conventional techniques are not economically operable unless highly subsidised.
The proposed technique combines two steps: a pre-treatment step followed by combustion. The pre-treament step shall not require drying of the solid waste and yield a hydrophobic coal-like solid (aka biocoal). The hydrophobicity of biocoal makes the separation of water efficient and less energy demanding. The biocoal shall be ready-to-use in existing power plants as the properties are very similar to lignite. Combination of these two steps can ensure a more favourable processing pathway for harnessing energy compared to other conventional routes.
Figure: Solid Waste to Biocoal