Innovative high efficiency filter for particulate matter from biomass flue gases

Solid biomass is considered a renewable energy source since, during the lifecycle, it determines a neutral CO2 balance and it is easily and continuously available. Due to its potential benefits, both economic and environmental, solid biomass has been recognized as a realistic alternative to traditional fossil fuels, above all to produce thermal power for domestic heating. Nevertheless, solid biomass combustion produces a great amount of particulate matter (PM), determining a negative impact on air quality, climate and human health. In particular, domestic biomass heating systems are one of the greatest sources of PM emissions. It derives from three main factors that makes residential biomass combustion inefficient: an incorrect operator behavior, improper operating conditions and a scarce quality of biomass. To address this issue in the short term, an effective solution could be the installation of a filtration device for the collection of PM in the biomass flue gases. This method is widely spread in the industrial sector, which shall comply whit stringent emission limits. In the residential sector, the high investment and maintenance costs and the complex management of a filter have limited its installation on domestic heating systems. However, to limit the impact of domestic biomass combustion, some scientific researches and the regulatory framework are now under development to successfully provide a PM filtration device for small-scale heating systems. In this paper, a review of the main PM filtration devices for domestic heating systems is conducted. These devices are based on the same technologies used in the industrial sector and they are near to the commercialization or under development. The technical and economic features of these technologies are analyzed to identify their strengths and weaknesses. An innovative high efficiency filter, developed by the Department of Industrial Engineering of the University of Bologna, is then presented. It was tested on a pilot plant consisting of a 25 kWth biomass boiler for residential use. The paper shows the preliminary experimental results, which demonstrates the promising impact (technical, environmental and economic) of the innovative filter in comparison with the other available technologies for domestic heating systems. The final aim is to demonstrate that the implementation of the innovative filter in residential size heating systems can really increase the sustainability of biomass combustion and further spread its plant marketability.