Evaluation of pollutant emissions from a hybrid oven (wood-fired and gas-fired)

Emission factors of the main air pollutants emitted by biomass burning (NOx, CO, PM, PAHs, OGC) were determined through the execution of experimental tests on an hybrid oven, which can operate both as a wood-fired oven and as a gas-fired one. Two different type of fuels were tested in the wood-fired operational mode: beechwood logs and beechwood briquettes. This essence was selected as it is currently the most widespread in Italian pizzerias, especially in the Northern part of the country. An ad-hoc sampling system was constructed by making reference to the UNI EN 16510-1:2019 technical standard and a new sampling protocol was designed to ensure reproducibilty of the tests. All the main phases of oven operation were investigated (cold-ignition, hot re-ignition, stationary cooking) and standard reference combustion cycles were defined for each one. The stationary phase was tested both with and without pizza cooking in order to evaluate the possible impact of this activity on the emissions of the oven. Based on the data obtained from the experimental tests, the pollutant emissions of the hybrid oven operated with the wood-burning mode fall within the wide range of values observed in literature for other wood-burning appliances, such as stoves and fireplaces [3]. Instead, tests on the oven used with the gas-firing mode show comparable emissions of NOx and a significant reduction in the concentrations of CO and PAHs. Moreover, the use of the gas-fired system enabled to shed light on the effect of pizza cooking on the emissions of OGC and PM. Indeed, by removing the contribution of wood-burning it was possible to highlight the significant impact of pizza cooking on the emissions of OGC during the stationary phase. Moreover, unlike the tests conducted in the wood-fired mode, a significant degree of condensation of semi-volatile organic compounds was observed in the dilution tunnel, as observed by the difference in concentration between particulate matter sampled on the hot and on the cold fumes. In the absence of specific legislation and/or regulations regarding the emissions of wood-fired pizza ovens, the experimental emission factors determined in this study were compared to the current EU policy regarding emission reduction from domestic combustion. Specifically, the observed values were compared to the 2020 Commentato [LR2]: To introduce subscripts and superscripts, please copy the selected letter/number/etc from this website (https://unicode-table.com/en/sets/superscript-and-subscript-letters/) and paste it in the text Commentato [LR1]: These instructions should not be removed Commentato [LR3]: Authorship format: M. Rossi¹*, F. Bianchi² and G. Verdi³ (* for presenting/corresponding authors -must coincide) Commentato [LR4]: Affiliation format: ¹Department of Chemistry, Università degli Studi di Torino, Via Pietro Giuria 7, 10125, Torino ORAL XXX 2 emission requirements for open fronted solid fuel local space heaters. The emissions of both the wood-fired and gas-fired ovens are below the thresholds with regards to NOx and CO, whereas concentrations of OGC and PM often exceed the imposed limits. In both cases, the pizza cooking activity has an important contribution to the emissions for the considered parameters, clearly distinguishable from the emissions deriving from the combustion of the fuel.