Comparative economical analysis of biogas production costs between standard wet anaerobic digestion and dry fermentation of biodegradable fraction of municipal solid waste

Abstract

Anaerobic biological treatment of biodegradable fraction of municipal solid waste has the opportunity to be an integral part of the solution to two of the most pressing environmental concerns of urban regions: waste management and renewable energy. Anaerobic digestion AD is a well-known biological treatment process of biodegradable fraction of municipal solid waste with an aim to produce biogas and in that way generate electricity. When speaking about anaerobic digestion we mostly refer to the so-called "wet" processes with total solids (TS) percentage between 15 and 25%. The biggest cost of the anaerobic digestion relates to treatment of percolate water produced during the AD process and increased investment in the AD plants because of the need for additional pre- and post treatment of biodegradable fraction of municipal solid waste. A few years ago, a new technology appeared on the market called Dry Fermentation (DF) as an alternative to anaerobic digestion. In the Dry Fermentation process total solids (TS) percentage is bigger than 50% which drastically decreases the amount of percolate water necessary to manage and treat subsequently. On the other hand, anaerobic digestion (AD) produces larger quantity of biogas (electricity), and in addition anaerobic digestion (AD) plants are more suitable for larger capacities of input waste material and they occupy less space. This thesis examines in depth differences between "wet" Anaerobic Digestion and Dry Fermentation and provides economical evaluation and comparison of two processes by taking into account most important advantages and disadvantages of both processes. It also gives precise information about influence of disposal cost and sale electrical energy tariff on the profitability of both type of technological plants.