Primary and secondary emissions of pellets and logwood residential heating appliances: emissions factors, secondary aerosol formation potential and chemical characterization

Abstract

International audienceTo decrease the dependence on fossil fuels and to limitglobal warming, the use of renewable energy hassignificantly increased over the last decade in Europe.Biomass energy has been largely promoted forresidential heating due to its (almost) neutralityconcerning CO2 emissions. However, residential woodcombustion accounts for an important source of airpollution as it emits large quantities of fine particulatematter (PM2.5), black carbon (BC) and volatile and semivolatileorganic compounds (VOCs and SVOCs) that areprecursors of secondary organic aerosol (SOA). Thequantity and composition of the emissions vary largelyaccording to the appliance, the fuel used and theoperating conditions. In particular, pellets appliancesare an interesting alternative to logwood ones due totheir lower primary emissions of PM2.5 and organicgaseous compounds (Olsen et al., 2020). To date, onlylimited information is available on the secondaryaerosol formation from pellets residential heatingappliances while several studies have shown the highSOA formation potential from logwood stoves emissions(Bertrand et al., 2017; Heringa et al., 2012). It istherefore urgent to evaluate the secondary emissions ofpellet devices as well as primary PM and BC emissions inorder to assess their impact on air quality. The aims ofthis study are to determine the emission factors ofprimary pollutants and secondary aerosol formationpotential of pellets and logwood appliances with adetailed chemical characterization of both gaseous andparticulate phases.Experiments have been carried out underdifferent output conditions (nominal and reduced) usingthree modern pellet boilers and stoves and one modernlogwood boiler and stove. In addition, two types ofpellets (soft and hard wood) have been tested. Afterdilution (20-40 times), biomass burning emissions wereaged through a potential aerosol mass-oxidation flowreactor (PAM-OFR) (Kang et al., 2007) at ambienttemperature and environmentally relevant relativehumidity (40-70%). Both daytime (with OH radical) andnight-time (with NO3 radical, only for the logwoodstove) chemistry have been investigated. Furthermore,“pure” secondary particles, formed by filtering (HEPAfilter) the entering emissions into the PAM-OFR, werealso studied. Primary and secondary emissions weremonitored using a high resolution-time of flight-aerosolmass spectrometer (HR-ToF-AMS), a scanning mobilityparticle sizer (SMPS), a condensation particle counter(CPC), a multi wavelength aethalometer, a TEOM-50(non-volatile PM fraction), a proton transfer reactiontime-of-flight mass spectrometer (PTR-ToF-MS) and gasanalyzers (CO2, O2, CO, NOx, total VOCs) providinginformation on the particulate and gaseous chemicalcomposition, particulate size distribution and numberconcentration. Moreover, effective particle density atdifferent aerosol size ranges have been investigated bycombining a differential mobility analyzer (DMA) and acentrifugal particle mass analyzer (CPMA). Finally,samples (filters and adsorbents) have been manuallycollected at the emission and after dilution forgravimetry and offline chemical analysis purposes.Primary (notably PM and BC) and secondaryemissions measured will be compared and discussed interms of wood appliances, output conditions and fuelused. Insights on the chemical composition of bothgaseous and particulate phases will be presented.This work was supported by ADEME (Agency forecological transition) under grant 206C0004 and theFrench Ministry of Environment