LANDFILL GAS ENERGY RECOVERY ECONOMIC AND ENVIRONMENTAL EVALUATION FOR A STUDY CASE

The present study is concerned with the economic and environmental evaluation of
landfill gas exploitation system in reference to an existing study case landfill, located in Tuscany
Region (Italy). Landfill gas production, during the different life phases of the study case landfill,
has been predicted according to a mathematical model, based on first-order decay equation,
considering different behaviours for different types of biodegradable wastes. On the basis of the
landfill gas collected yearly it is possible to estimate the appropriate size and number of
reciprocating engines required every year for the landfill gas exploitation. As a matter of fact,
during the energy recovery time, different combinations of engine sizes and numbers can be
adopted to exploit the landfill gas: the selection of the final combination was carried out with the
aim of maximising the profits coming from the balance of energy system investment and
maintenance costs and electric energy selling earnings. Two scenarios were compared from an
economic point of view, highlighting the one with the maximum economic profits. The scenarios
were also compared from an environmental point of view, evaluating the overall contribution to
Greenhouse Effect from escaped landfill gas, collected and combusted landfill gas and recovered
electric energy avoided emissions.