Landfill gas utilisation for thermal and electric energy cogeneration

Landfill gas (LFG) has been widely used overseas for decades, but it is often ignored in Hong Kong. This paper explores a LFG cogeneration technology for electric power production using internal combustion engines and space cooling using indirect absorption chillers. Low-temperature waste heat is also recovered for hot water production. In this Combined Heat & Power with Absorption Cooling (CHPAC) scheme, three kinds of common building energy demands (ie electricity, chilled water and hot water) are simultaneously produced with LFG as fuel. Experimental data were obtained from an operating Landfill Gas-To-Electricity (LFGTE) system at the Jordan Valley Landfill for a partial verification exercise. The potential utilisation of the CHPAC scheme in different building premises was investigated. With particular focus on the CHPAC scheme implementation in hotels, a feasibility study was conducted with respect to the technical viability, economical attractiveness and environmental benefits. Using a hypothetical 40,000 m2hotel, an annual cost savings of HK$4.8 million was estimated, with capital investment ranging from HK$14–20 million and a payback period between 4 to 10 years. At the same time, annual CO2and CH4emission reductions equivalent to over 1,800 tons and 10,000 tons, respectively, were achieved.