Feasibility of a food waste to energy system in high-rise buildings

Abstract

Hong Kong is currently generating more than 3000 tons of food waste every day which generate air pollution problem and create odor nuisance to residents near landfill site. It is critical for us to reduce waste generation at sources and find ways to treat our food waste instead of solely rely on landfill. The aim of this paper is to propose a food waste to energy system to be installed in high-rise buildings which helps save our landfill space and utilize waste energy to generate electricity and heat for building use. It is estimated that around one ton of food waste will be generated from a domestic household building and hence the proposed food waste to energy system is designed to have treatment capacity of 1 ton of food waste per day. A total of 238.1 Nm3 of biogas, with 53.5% methane content can be generated from one ton of food waste. With the use of combined heat and power (CHP) system, 465 kWh of electricity and 732 kWh of heat can be generated. A survey is conducted to assess the public view of the food waste problem in Hong Kong and the proposed food waste to energy system. It is found that most of the respondent agrees the proposed food waste to energy is a good mean to tackle food waste problem in Hong Kong and support to install such system in high-rise buildings. A life cycle assessment is carried out to compare the environmental impact of landfilling 1 ton of food waste and treating 1 ton of food waste with the proposed system. It is found that the carbon emission (CO2 equivalent) of the proposed system is 1112.6 kg less than that of landfilling, i.e. the proposed system can help to save 406.1 ton of carbon dioxide emission a year which equals to planting of 17,656 trees. The economic viability of installing the proposed system is evaluated. The capital investment and the operating cost for the proposed system are estimated to be HK$3,400,000 and HK$ 170,000 per year respectively. As the proposed system can bring in revenue of HK$ 763,986 per year, the internal rate of return (IRR) and payback period of the system is 15% and 6 years respectively. Limitations and difficulties encountered for the installation of the proposed system are discussed and finally suggestions are made for the successful installation of the proposed system and several ways to reduce food waste from sources are also suggested for both commercial sectors and the government.