Assessing residential biomass combustion emissions in the Marche Region, Italy, through a high-resolution bottom-up methodology

The estimation of airborne pollutant emissions caused by residential biomass combustion is a critical challenge in regional air quality assessment, especially due to the lack of accurate data on fuel consumption and the common use of biomass outside official markets. National inventories often adopt a top-down approach based on aggregated statistical sources and generalized emission factors, which may not reflect real consumption patterns and combustion technologies at the local level. This study compares a top-down methodology with a bottom-up approach developed specifically for the Marche Region (Italy), aiming to build a more accurate regional emission inventory. The bottom-up method is based on a 2023 household survey involving over 9,700 respondents, of whom 31% reported using biomass for heating. Where statistically reliable, data were used to generate municipality-level estimates; otherwise, emissions were calculated for grouped municipalities with similar geographic, climatic (heating degree days), and administrative characteristics. Technology-specific emission factors (Tier 2) from the EMEP/EEA guidebook were applied. The results show significantly higher biomass consumption and associated emissions – especially PM10, PM2.5 and NOx – compared to national and regional inventories based on top-down assumptions. This work highlights the added value of locally grounded bottom-up data in improving the spatial and quantitative accuracy of regional emission inventories and supports the adoption of hybrid or revised national approaches that better capture realworld dynamics.