Dry Anaerobic Conversion of Municipal Solid Waste by Means of the Dranco Process

The Dranco process has been developed for the conversion of solid organic wastes, specifically the organic fraction of municipal solid waste (MSW), to energy and a humus-like final product, called Humotex. The Dranco process can be compared to landfill gas production, accelerated by a factor 1000. A Dranco installation with a digester of 808 m³ treating 10,500 tons of source separated waste per year will be constructed in 1991 at Brecht, Belgium. A description of the plant is elaborated. A demonstration plant of 56 m³ has been in operation for several years in Gent, Belgium using mixed garbage as a feedstock. The operating temperature in the digester is 55°C and the total solids concentration is ca. 32%. The mean gas production rate is 3.33 Nm³ CH₄/m³_reactor.day. The volumetric loading is 17.3 kg COD/m³_reactor.day and the COD reduction is 55%. The gas production process is finalized in 3 weeks. The final product is dewatered and further stabilized in a 10 day aerobic post-treatment. The Humotex is free of pathogens. Low concentrations of heavy metals can only be obtained through separate collection of garbage. The Dranco process then also focusses on the digestion of source separated waste such as vegetable, fruit, garden and non-recyclable paper waste.