Physical-chemical and microbiological characterization, and mutagenic activity of airborne PM sampled in a biomass-fueled electrical production facility

Dust and Particulate Matter Generated during Handling and Pelletization of Herbaceous Biomass: A Review

Using straw and herbaceous crops to replace or augment fossil fuels is becoming popular as access to forest biomass becomes environmentally stricter and more expensive. The low bulk density raw biomass is pre-processed and densified into pellets to facilitate handling and use. Dust is generated during collection, baling and debaling, grinding, drying, and densifying processed herbaceous biomass. Abundant literature deals with dust generated during the industrial handling of woody biomass, grains, and other crops like cotton. But the information on handling herbaceous biomass in the open literature is scarce. This paper reviews the available literature on dust generation from handling and processing of herbaceous biomass. Limited available data shows that herbaceous biomass species have a lower ignition temperature than woody biomass. The paper identifies several crucial pieces of information needed to ensure safety in the handling and pelleting of herbaceous crops.

A characterization of bioaerosols in biowaste pretreatment plants in relation to occupational health

Occupational exposure to microorganisms can be associated with adverse health outcomes. In this study, we assessed exposure to bioaerosols in two biowaste pretreatment plants in Denmark, which differed in location (city or countryside) and how they were built ('closed-off processes' or 'open processes'). Bioaerosol exposures were characterized by microbial concentrations in personal, stationary, sedimented dust, and hand samples, and their size distribution was assessed. Furthermore, species were identified by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF MS), and inhalable dust, endotoxin, biofilm production, the total inflammatory potential, and fungicide resistance to four fungicides (amphotericin B, caspofungin acetate, itraconazole, voriconazole) were determined. Bacterial and fungal concentrations were on average (GM) in the order of 10⁴ cfu/m³, but ranged from 10² to 10⁸ cfu/m³. Several species which may cause health problems were identified. Personal endotoxin exposures were on average 28 EU/m³, but both personal and stationary samples ranged from 0.6 to 2035 EU/m³. Bioaerosols had the potential to form biofilms and to induce inflammation as measured in a human cell line. Exposures were higher in the plants that outdoor reference values. Higher exposures were found in the 'open process' plant, such as in microbial concentrations, species richness, endotoxin, biofilm production, and the total inflammatory potential. Six out of 28 tested Aspergillus fumigatus isolates were resistant to fungicides (amphotericin B and voriconazole). In conclusion, there is a high exposure to bioaerosols during work in biowaste pretreatment plants, however, results also suggests that how the plant is built and functions may affect the exposures.

Generation of Viable Bacterial and Fungal Aerosols during Biomass Combustion

Biomass combustion is known to be one of the main contributors to air pollution. However, the influence of biomass burning on the distribution of viable bacterial and fungal aerosols is uncertain. This study aimed to examine survivability of bacteria and fungi in the post-combustion products, and to investigate the aerosolization of viable cells during combustion of different types of organic materials. Laboratory experiments included a small-scale combustion of organic materials contaminated with microorganisms in order to determine the survivability of microbes in the combustion products and the potential aerosolization of viable cells during combustion. Field experiments were completed during intentional and prescribed biomass burning events in order to investigate the aerosolization mechanisms that are not available at the laboratory scale. Laboratory experiments did not demonstrate aerosolization of microorganisms during biomass combustion. However, the relatively high survival rate of bacteria in the combustion products ought to be accounted for, as the surviving microorganisms can potentially be aerosolized by high velocity natural air flows. Field investigations demonstrated significant increase in the bioaerosol concentration above natural background during and after biomass combustion.

Formation mechanism and spectroscopy of C6H radicals in extreme environments: a theoretical study

This study examined the reaction mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/CBS//B3LYP/6-311G(d,p) calculations followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results demonstrate that the initial reaction begins with the formation of an intermediate 3i2 with an entrance barrier of 3.0 kcal mol-1 and an intermediate 1i1 without entrance barriers. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and variational transition-state theories for determining the collision energies between 5 kcal mol-1 and 25 kcal mol-1 demonstrate that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products. The electronic absorption spectra of solid neon matrices in the range of 17 140-22 200 cm-1 were obtained by Maier et al., and the optimized ground and excited state structures of C6H were used to simulate the absorption spectra by one-photon excitation equations. The displaced harmonic oscillator approximation and the Franck-Condon approximation were used to simulate the absorption spectrum of the B2Π ← X2Π transition of C6H. This indicates that the vibronic structures were dominated by one of the six active completely symmetric modes, with v3 being the most crucial.

Comparison of Mutagenic Activities of Various Ultra-Fine Particles

Air pollution is increasing, along with consumption of fossil fuels such as coal and diesel gas. Air pollutants are known to be a major cause of respiratory-related illness and death, however, there are few reports on the genotoxic characterization of diverse air pollutants in Korea. In this study, we investigated the mutagenic activity of various particles such as diesel exhaust particles (DEP), combustion of rice straw (RSC), pine stem (PSC), and coal (CC), tunnel dust (TD), and road side dust (RD). Ultra-fine particles (UFPs) were collected by the glass fiber filter pad. Then, we performed a chemical analysis to see each of the component features of each particulate matter. The mutagenicity of various UFPs was determined by the Ames test with four Salmonella typhimurium strains with or without metabolic activation. The optimal concentrations of UFPs were selected based on result of a concentration decision test. Moreover, in order to compare relative mutagenicity among UFPs, we selected and tested DEP as mutation reference. DEP, RSC, and PSC induced concentration-dependent increases in revertant colony numbers with TA98, TA100, and TA1537 strains in the absence and presence of metabolic activation. DEP showed the highest specific activity among the particulate matters. In this study, we conclude that DEP, RSC, PSC, and TD displayed varying degrees of mutagenicity, and these results suggest that the mutagenicity of these air pollutants is associated with the presence of polycyclic aromatic hydrocarbons (PAHs) in these particulate matters.

The Use of Biomass for Electricity Generation: A Scoping Review of Health Effects on Humans in Residential and Occupational Settings

The utilization of biomass for power generation has become more prevalent globally. To survey the status of evidence concerning resulting health impacts and to depict potential research needs, a scoping-review was conducted. Biomass life cycle phases of interest were the conversion and combustion phases. Studies from occupational and residential settings were considered. The scoping review was conducted systematically, comprising an extensive literature search, a guided screening process, in-duplicate data extraction, and critical appraisal. Two reviewers executed most review steps. Nine articles of relevance were identified. In occupational settings of biomass plants, exposure to endotoxins and fungi might be associated with respiratory disorders. An accidental leakage of hydrogen sulfide in biogas plants may lead to fatalities or severe health impacts. Living near biomass power plants (and the accompanied odorous air pollution) may result in an increased risk for several symptoms and odor annoyance, mediated by perception about air pollution or an evaluation of a resulting health risk. The methodological quality of included studies varied a lot. Overall, the body of evidence on the topic is sparse and future high-quality research is strongly recommended.

Potential Occupational Exposures and Health Risks Associated with Biomass-Based Power Generation

Biomass is increasingly being used for power generation; however, assessment of potential occupational health and safety (OH&S) concerns related to usage of biomass fuels in combustion-based generation remains limited. We reviewed the available literature on known and potential OH&S issues associated with biomass-based fuel usage for electricity generation at the utility scale. We considered three potential exposure scenarios--pre-combustion exposure to material associated with the fuel, exposure to combustion products, and post-combustion exposure to ash and residues. Testing of dust, fungal and bacterial levels at two power stations was also undertaken. Results indicated that dust concentrations within biomass plants can be extremely variable, with peak levels in some areas exceeding occupational exposure limits for wood dust and general inhalable dust. Fungal spore types, identified as common environmental species, were higher than in outdoor air. Our review suggests that pre-combustion risks, including bioaerosols and biogenic organics, should be considered further. Combustion and post-combustion risks appear similar to current fossil-based combustion. In light of limited available information, additional studies at power plants utilizing a variety of technologies and biomass fuels are recommended.