Composition of ashes from the combustion of solid fuels and municipal waste in households.

In this study, 73 ash samples (comprising 49 ash samples from combustion tests performed in 2017, and 24 ash samples from combustion tests performed during 2014-2016 at the Energy Research Center, Ostrava, Czech Republic) were analysed. Ash samples were obtained via the combustion of various solid fuels, their mixtures with municipal waste (floor coverings, paper, polyethylene terephthalate (PET) briquettes, plastics, and textiles), and municipal wood waste (furniture chipboard, window frames) in household combustion units, such as an overfire boiler, boiler with downdraft combustion, gasification boiler, automatic boiler, and stove. The aim of this study was to determine the composition of representative ash samples from solid fuels and municipal waste and to determine which parameters (metals and halides) were present in the ash analysis after waste incineration. Statistical evaluation of box plots with the determination of the boundaries for outliers and extreme values was performed. Finally, six metals (Sb, Cu, Pb, Sn, Ti, and Zn), together with chlorides, were taken as the indicators of municipal waste incineration in households. The highest value of Sb was 344 mg/kg in plastics + dry beech; the highest value of Cu was 30,500 mg/kg in textiles + black coal (B1); the highest concentration of Pb was 1,360 mg/kg in floor coverings + dry beech; the highest value of Sn was 108 mg/kg in textiles + dry beech; the highest concentration of Ti was 38,200 mg/kg in window frames; the highest value of Zn was 215,000 mg/kg in window frames; and the highest concentration of chlorides was 191,000 mg/kg in floor coverings + dry beech.

Influence of co-combustion of unsuitable fuels with standardized fuels in households on CO, OGC, PM, and PAH emissions.

Waste combustion in residential small-scale combustion units is not legal in the Czech Republic or other European Union countries. The resulting gaseous and particulate pollutants expose inhabitants to smells and toxic compounds and may damage their property and health. This study is designed to define the emissions of gaseous and particulate pollutants and determine the influence of municipal waste combustion on emission factors. Different types of solid fuels, municipal wood wastes (window frames, furniture chipboard), and mixtures of solid fuels with municipal wastes (namely, textiles, plastics, PET briquettes comprising a mixture of PET bottles + wood pellets + frying oil, paper, and floor coverings) were combusted in residential combustion units (such as gasification boiler, boiler with down-draft combustion, overfire boiler, and stove). Studies describing such an extensive range of waste samples combusted in different small-scale combustion units have not yet been published. Emission factors (EFs) for products of incomplete combustion (carbon monoxide (CO), organic gaseous compounds (OGC), and polycyclic aromatic hydrocarbons (PAHs) in gaseous and particulate phases) and particulate matter (PM) were within narrow intervals and lowest for standardized wood fuel (dry wood logs only) and 2-4 times higher on average for unsuitable coal samples (coal unsuitable for the particular boiler type used and coal combined with waste), for which values fell within broad intervals.The EFs of pollutants resulting from incomplete combustion (CO, OGC, and 16 PAHtotal) and PM were lowest for standardized wood fuel (dry wood logs only) and almost two or four times higher on average for unsuitable coal fuels (coal unsuitable for the particular boiler type used and coal combined with waste).

Effect of fuels and domestic heating appliance types on emission factors of selected organic pollutants.

This study reports on the first complex data set of emission factors (EFs) of selected pollutants from combustion of five fuel types (lignite, bituminous coal, spruce, beech, and maize) in six different domestic heating appliances of various combustion designs. The effect of fuel as well as the effect of boiler type was studied. In total, 46 combustion runs were performed, during which numerous EFs were measured, including the EFs of particulate matter (PM), carbon monoxide, polyaromatic hydrocarbons (PAH), hexachlorobenzene (HxCBz), polychlorinated dibenzo-p-dioxins and furans (PCDD/F), etc. The highest EFs of nonchlorinated pollutants were measured for old-type boilers with over-fire and under-fire designs and with manual stoking and natural draft. Emissions of the above-mentioned pollutants from modern-type boilers (automatic, downdraft) were 10 times lower or more. The decisive factor for emission rate of nonchlorinated pollutants was the type of appliance; the type of fuel plays only a minor role. Emissions of chlorinated pollutants were proportional mainly to the chlorine content in fuel, but the type of appliance also influenced the rate of emissions significantly. Surprisingly, higher EFs of PCDD/F from combustion of chlorinated bituminous coal were observed for modern-type boilers (downdraft, automatic) than for old-type ones. On the other hand, when bituminous coal was burned, higher emissions of HxCBz were found for old-type boilers than for modern-type ones.

Influence of boiler output and type on gaseous and particulate emissions from the combustion of coal for residential heating.

The study describes gaseous and particulate emissions from the combustion of two types of coal (hard and brown) in three types of boilers (one modern-type and two old-type boilers) used for residential heating. The importance of the heat outputs (nominal and two reduced outputs) for the emission of pollutants was also studied. Three outputs (95-108%, 58-73% and 26-50%) covered the expected operation of these boilers in real households under different outdoor air temperatures in the winter. Gaseous components (NOx, SO2, CO, CO2, OGC) and particulate organic compounds (n-alkanes, polycyclic aromatic hydrocarbons, hopanes) were determined in the emissions. In general, the emission factors (EFs) of the products of incomplete combustion were higher from the combustion of coal in old-type boilers than from that in the modern-type boilers. The EFs of particulate matter varied between 11.6 and 17.0 g kg-1 (hard coal, the oldest-type boiler), and 0.290 and 0.544 g kg-1 (brown coal, the modern-type boiler). The trends between the EFs of particulate organic compounds and the outputs of boilers were observed only with the automatic boiler (modern-type boiler). Similar trends for old-type boilers were not observed, probably due to the high instability of the combustion process as a result of the old construction of these boilers. Diagnostic ratios of the PAHs and the homohopane index, used for source apportionment of particulate matter in ambient air, were calculated. While the calculated homohopane indexes were similar to those reported in the literature, the calculated diagnostic ratios for PAHs related to coal combustion were different.

Effects of braking conditions on nanoparticle emissions from passenger car friction brakes.

Automobile friction brakes generate, in addition to coarse particles generated by mechanical processes, highly variable amount of nanoparticles from high temperature processes. The effects of braking conditions - speed, deceleration rate, brake rotor temperatures - on nanoparticle production were investigated here, aiming to provide practical guidance for reducing emissions through driving style and traffic management. Typical brake pads and a rotor from a common passenger car were subjected, on a brake dynamometer, to three runs of the WLTP brake cycle developed for brake wear particle measurements. Additionally, four sets of common brake pads were subjected to those parts of standardized brake performance tests believed to be reasonably realistic for common driving. Particle size distributions (5.6-560 nm electric mobility diameter, without removal of volatiles) show a dominant peak at 10 nm commensurate to the severity of braking and a non-linear increase of the total particle number at higher braking powers and higher total energy dissipated. The average emissions for three runs of the WLTP brake cycle were 3.3 × 1010 particles/km, while the harshest deceleration, 175-100 km/h at 5.28 m·s-2, has produced 8.4 to 38 × 1013 particles, corresponding to 2.5-11.5 thousands of km of WLTP-like driving. While previous studies have correlated higher PN production with higher average brake rotor temperature, a more complex relationship between nanoparticle emissions and a combination of initial rotor temperature, total energy dissipated and braking power has been observed here. From a driver behavior and regulatory perspective, it appears limiting harsh braking and braking from high speeds, possibly through improved driving practices, road design and traffic management, may potentially reduce brake wear nanoparticles. From the measurement perspective, it appears that "off-cycle" braking, even if relatively infrequent, may be associated with exponentially higher emissions and non-negligible share of the total emissions, and therefore should not be neglected.

Real Operating Parameters of Bioethanol Burners in Terms of Heat Output.

The aim of this study was to determine the operating parameters of bioethanol burners used in the so-called bioethanol fireplaces, mainly in terms of their actual heat output. The method used to determine the actual heat output was designed considering procedures from the standard EN 16647 fireplaces for liquid fuel. Experiments were carried out on eight different types of burners with two different types of fuels. The measurements demonstrated a difference of up to 19% in the maximal heat output among individual fuels and a difference of up to 16% in the average heat output when comparing identical burners over approximately 60 min of operation. The average heat outputs of the burners during the measurements reached approximately 41-62% of the heat output declared by the manufacturers. The measured values were used to create graphs of the dependency of the burner opening size on its average heat output based on the fuel type. Two-chambered burners reached a higher average heat output than single-chambered burners with the same burner opening area of above ∼6000 mm2. The positions of the regulation damper (75 and 50%) increased the burning time by 21 and 86%, respectively.

Comparison of emissions of gaseous and particulate pollutants from the combustion of biomass and coal in modern and old-type boilers used for residential heating in the Czech Republic, Central Europe.

The chemical composition of emissions from old-type (an overfire boiler, a boiler with down-draft combustion) and modern-type (an automatic and a gasification boiler) boilers was compared. The boilers were operated with different fuels (brown and hard coal, wet and dry wood, wood pellets and brown coal briquettes) with reduced output (40-60%). The emissions were characterized by the contents of gaseous components (NOx, SO2, CO, CO2, OGC); and particulate organic compounds (alkanes, polycyclic aromatic hydrocarbons, saccharides), including organic markers (monosaccharide anhydrides, diterpenoids, methoxyphenols, hopanes), which are used for source apportionment of particulate matter in ambient air. In general, emissions of the products of incomplete combustion (CO, particles, polycyclic aromatic hydrocarbons) were higher from the combustion of solid fuels in old-type boilers than from that in modern-type boilers. The modern-type (especially automatic) boilers were the most environmentally friendly. The highest concentrations of particulate matter (81.6-89.4 g kg-1) and particulate organic compounds (sum of PAHs: 225-275 mg kg-1) including organic markers were found in emissions from old-type (overfire) boilers, especially with the combustion of brown and hard coal. Characteristic ratios of selected organic compounds/markers applied for source identification were calculated. Computed characteristic ratios for monosaccharide anhydrides (biomass combustion) agreed with values in the literature. Homohopane indexes, frequently used for identification of coal combustion, and other characteristic ratios for PAHs, were different from the literature data. In our opinion, characteristic ratios for PAHs are not suitable for use in source apportionment.

The impact of co-combustion of polyethylene plastics and wood in a small residential boiler on emissions of gaseous pollutants, particulate matter, PAHs and 1,3,5- triphenylbenzene.

The aim of this study was to simulate a banned but widely spread practice of co-combustion of plastic with wood in a small residential boiler and to quantify its impact on emissions of gaseous pollutants, particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and 1,3,5-triphenylbenzene (135TPB), a new tracer of polyethylene plastic combustion. Supermarket polyethylene shopping bags (PE) and polyethylene terephthalate bottles (PET) were burnt as supplementary fuels with beech logs (BL) in an old-type 20 kW over-fire boiler both at a nominal and reduced heat output. An impact of co-combustion was more pronounced at the nominal heat output: an increase in emissions of PM, total organic carbon (TOC), toxic equivalent (TEQ) of 7 carcinogenic PAHs (c-PAHs) and a higher ratio of c-PAHs TEQ in particulate phase was observed during co-combustion of both plastics. 135TPB was found in emissions from both plastics both at a nominal and reduced output. In contrast to findings reported in the literature, 135TPB was a dominant compound detected by mass spectrometry on m/z 306 exclusively in emissions from co-combustion of PE. Surprisingly, six other even more abundant compounds of unknown identity were found on this m/z in emissions from co-combustion of PET. One of these unknown compounds was identified as p-quaterphenyl (pQ). Principal component analysis revealed strong correlation among 135TPB, pQ and five unknown compounds. pQ seems to be suitable tracers of polyethylene terephthalate plastic co-combustion, while 135TPB proved its suitability to be an all-purpose tracer of polyethylene plastics combustion.

PAH emissions from old and new types of domestic hot water boilers.

Five different domestic heating boilers (automatic, over-fire, with down-draft combustion and gasification) and three types of fuel (lignite, wood and mixed fuel) were examined in 25 combustion tests and correlated with the emissions of particulate matter (PM), carbon monoxide (CO), total organic carbon (TOC) and 12 polycyclic aromatic hydrocarbons (PAHs with MW = 178-278 g/mol) focusing on particle phase. However, the distribution of 12 PAHs in gas phase was considered as well due to the presence mainly of lighter PAHs in gas phase. The PAHs, as well as the CO and TOC, are the indicators of incomplete combustion, and in this study PAH emission increased significantly with increasing emissions of CO and TOC. The PAHs were mainly detected on PM2.5, their contents were increasing linearly with increasing PM2.5 emissions. The highest emission factors of PAHs were measured for boilers of old construction, such as over-fire boiler (5.8-929 mg/kg) and boiler with down-draft combustion (3.1-54.1 mg/kg). Modern types of boilers produced much lower emissions of PAHs, in particular, automatic boiler (0.3-3.3 mg/kg) and gasification boilers (0.2-6.7 mg/kg). In general, the inefficient combustion at reduced output of boilers generated 1.4-17.7 times more emissions of PAHs than the combustion at nominal output of boilers. It is recommended to operate boilers at nominal output with sufficient air supply and to use the proper fuel to minimise PAHs emissions from domestic heating appliances.