A hybrid biogas system for Kolkata

Municipal solid waste (MSW) is a global problem. Four processes for treatment include landfilling, incineration, recycling and composting the organic fraction. Landfilling can cause the release of the potent greenhouse gas methane into the atmosphere. In many parts of the world, including the European Union, legislation to limit the amount of generated Organic Fraction Municipal Solid Wastes (OFMSW) going to landfill has been introduced. An alternative to landfilling is to anaerobically digest the OFMSW. This paper investigates the concept of a Hybrid Biomass System (HBS) consisting of solar thermal Flat Plat Collector (FPC) providing heat energy to the thermophilic (55oC) anaerobic digestion process, and the potential energy yield of hotel OFMSW in Kolkata. The methodology comprises development and assessment of a theoretical model representing the anaerobic digestion process for optimum biogas yield and TRNSYS simulation of a 5m2 and 10m2 FPC. Theoretical biogas production rates derived are 0.44m3/kgVS or 0.21m3 biogas/guest/day with a C/N ratio of 35:1. 5m2 and 10m2 FPC simulations maintained the thermophilic temperature of 55oC within -1.9 and +2.1. 10m2 FPC provides largest energy contribution at 11% of the annual energy requirement. In is concluded that FPCs can support thermophilic digester heating requirements with heat store or direct integration. In order to meet optimum biogas yield, legislation and policy is required to evolve the current waste management processes with emphasis on infrastructure development and source segregation.