Municipal residual waste (RW) produced in the Venice area undergoes mechanical-biological treatment (MBT) in the Fusina plant to produce refuse-derived fuel (RDF) that is then co-combusted in a nearby coal-fired power station. Being the first significant project for RDF co-firing in power plants in Italy, a number of different testing phases were performed starting in 2003, aimed at evaluating differences between so-called blank operation (i.e., with only coal feeding) and RDF co-firing at different feeding rates.
The analysis of data gathered during the industrial experimentation shows a savings of 0.7 tonnes (t) of coal per each tonne of co-fired RDF; stack concentrations of some pollutants (hydrochloric acid [HCl], ammonia [NH3], carbon monoxide [CO], chromium [Cr], and lead [Pb]) appear slightly higher during co-combustion compared with blank operation, whereas concentrations of dust, sulfur oxides (SOx), and some metals (manganese [Mn], nickel [Ni], vanadium [V]) are lower.
To assess the overall environmental performance of this practice, a life cycle assessment (LCA) study was then performed, where different strategies of energy recovery from RW were compared: production of RDF and its co-combustion in the Fusina power plant, RW combustion without any pretreatment in a mass-burn waste-to-energy (WTE) plant, and production of RDF and its combustion in a dedicated WTE plant.
The LCA results show that co-combustion of RDF performs better than the other strategies for all impact categories evaluated. The only exception is when the WTE plant operates in combined heat and power mode, with very high overall conversion efficiencies.