Stima del consumo di legna per riscaldamento domestico in Lombardia: metodologia di indagine e implicazioni ambientali

A survey has been undertaken in order to predict the contribution of wood combustion to domestic heating in Lombardy by means of about 98.000 questionnaires sent to students of 386 middle schools, with questions on the wood amount used, the modalities of use and the types of combustion systems utilized. The analysis of the 33.000 questionnaires filled and the statistical elaborations performed through the clusterization of the municipalities have brought to an estimate of wood burning by 3,9 million families of the region. Even though the type of statistical population taken into account in the research, the middle schools students’ families, cannot be directly extrapolated to the entire population of families of the region, the details about the utilization rates in different provinces and the partition in type of combustion system, kind of house and the location of the municipalities most likely are not significantly affected by the particular sample selected by the survey. The total amount of wood burnt in Lombardy in the 2003-2004 winter season has been estimated in about 2,5 million tonnes, with a confidence interval of 95% between 1,9 and 3,1 Mt/year. The considerable wood quantities estimated in the survey are of great importance in relation to two crucial environmental issues: on one hand the use of biomass of photosynthetic origin for domestic heating implies a greenhouse gas emission saving, quantified in approximately 2% of the relative total emissions in Lombardy, but on the other hand the consistent use of conventional devices with low efficiency and quality of combustion involves a primary PM10 emission estimated as 25% of the regional PM10 emissions.