Emission factors for PM2.5, CO, CO2, NOx, SO2 and particle size distributions from the combustion of wood species using a new controlled combustion chamber 3CE

Study of sugarcane bagasse/straw combustion and its atmospheric emissions using a pilot-burner

This work conducted experimental combustion on a closed chamber using two different materials: mixture (1:1) sugarcane bagasse/straw and pre-treated biomass. The sampling method was an Andersen cascade impactor with eight stages. Tests were carried out on untreated biomass varying the velocities observed in the sampling duct (4.18; 5.20, 6.85, and 8.21 m.s-1). Pre-treated biomass tests were performed at 4.19 m.s-1 because in this condition there is a higher speed stability inside the duct. During the combustion tests, the concentration of emitted particles was higher for the lower speed range, with an order of 4.19 > 5.40 > 6.85 > 8.21 m.s-1. The higher speeds observed inside the duct behaved as a dragging agent for particulate material. For the tests at the speed of 8.21 m.s-1 where the flow inside the duct was 0.088 m3s-1, this behavior is more evident. Considering the fine diameter particles (< 2.5 µm), they were emitted in a higher concentration, due to the biomass combustion process, which results in higher emission of ultrafine particles. The emission factors (EFs) obtained for PM10 for untreated biomass were in the range of 0.414 and 0.840. On the other hand, considering the pre-treated biomass, these factors were 0.70 and 1.51. The EFs of PM from the burning of the pre-treated biomass were higher when compared to untreated biomass, which is mainly due to the higher temperature of the process due to the higher HHV (higher heating value) of this material, caused by the removal of hemicellulose (4.71 times) and a proportional increase in lignin (1.52 times). Biomass combustion has the potential to partially replace fossil fuels in heat and energy generation. Nevertheless, more stringent and comprehensive legislation should be established to ensure that air quality is maintained. Furthermore, the emission factors obtained in this study might be useful as input data for air quality modeling in the context of sugarcane's burning biomass, thus, contributing to the generation of inventories that include emissions of this nature.

Evaluation of the efficiency of a Venturi scrubber in particulate matter collection smaller than 2.5 µm emitted by biomass burning

Energy demand has increased worldwide, and biomass burning is one of the solutions most used by industries, especially in countries that have a great potential in agriculture, such as Brazil. However, these energy sources generate pollutants, consisting of particulate matter (PM) with a complex chemical composition, such as sugarcane bagasse (SB) burning. Controlling these emissions is necessary; therefore, the aim was to evaluate PM collection using a rectangular Venturi scrubber (RVS), and its effects on the composition of the PM emitted. Considering the appropriate use of biomass as an industrial fuel and the emerging need for a technique capable of efficiently removing pollutants from biomass burning, this study shows the control of emissions as an innovation in a situation such as the industrial one with the use of a Venturi scrubber in fine particle collection, in addition to using portable and representative isokinetic sampling equipment of these particles. The pilot-scale simulation of the biomass burning process, the representative sampling of fine particles and obtaining parameters to control pollutant emissions for a Venturi scrubber, meets the current situation of concern about air quality. The average collection efficiency values were 96.6% for PM_{> 2.5}, 85.5% for PM_1.0-2.5, and 66.9% for PM_{< 1.0}. The ionic analysis for PM_{< 1.0} filters showed potassium, chloride, nitrate, and nitrite at concentrations ranging from 20.12 to 36.5 μg/m³. As the ethanol and sugar plants will continue to generate electricity with sugarcane bagasse burning, emission control technologies and cost-effective and efficient portable samplers are needed to monitor particulate materials and improve current gas cleaning equipment projects.

Accumulation of functional metabolites and transcriptomics in postharvest fume-drying and air-drying process in rhubarb

BACKGROUND

The active component content is an important factor affecting quality of traditional Chinese medicines. The fume-drying process can effectively improve the content of active components in rhubarb, but the accumulation dynamics and molecular mechanisms are not known. In this study, variations in the active components of rhubarb during the drying process were determined, and the most intense changes in the active components were preferred for transcriptome inquiry.

RESULTS

The results showed that the accumulation of active ingredients could be significantly promoted in the early stage of fume-drying and air-drying. In particular, the active ingredients increased by 61.57% (from 44.58 to 72.02 mg g^-1 ) on the fourth day of fume-drying. A total of 4191 DEGs (differentially expressed genes) were identified by transcriptome analysis when the active components changed significantly. Transcriptome data of different dried rhubarb samples revealed, that the fume-drying process could significantly improve the expression of genes relevant to respiration, phenolic acid, and anthraquinone synthesis pathways in rhubarb, which was more conducive to the synthesis and accumulation of the active components.

CONCLUSION

Fume-drying stimulated respiration and secondary metabolite synthesis in rhubarb cells by exerting strong external stress on freshly harvested rhubarb. This study revealed the variations and molecular mechanism of active component accumulation in the rhubarb drying process and might serve as a guide for the development of alternative methods for rhubarb fumigation and drying process. © 2022 Society of Chemical Industry.

How does biased technological progress affect haze pollution? Evidence from APEC economies

Biased technological progress is the act of energy conservation and emission reduction by changing the marginal rate of substitution. In this study, we introduced renewable energy into a production function, and proposed a method of identifying biased characteristics of technological progress, based on marginal productivity theory. A panel dataset for the Asia-Pacific Economic Cooperation (APEC) economies from 2000 to 2017 was analyzed to explore the effect of biased technological progress in reducing particulate matter (PM_2.5). We found that input biased technological progress tended to use more non-renewable energy. Input biased technological progress aggravated haze pollution; however, this effect decreased as the PM_2.5 concentration increased. Output biased technological progress significantly reduced haze pollution in high-income economies, but increased it in low-income economies. The effect of neutral technological progress on haze pollution was the opposite of the effect from output biased technological progress. We also found that increasing renewable energy consumption and reducing energy intensity were separate effective paths for input and output biased technological progress, respectively, to mitigate haze pollution. For neutral technological progress, improving total factor productivity was an important way to mitigate haze pollution. Finally, several policy recommendations are proposed to mitigate haze pollution in APEC economies.

A critical review of pollutant emission factors from fuel combustion in home stoves

A large population does not have access to modern household energy and relies on solid fuels such as coal and biomass fuels. Burning of these solid fuels in low-efficiency home stoves produces high amounts of multiple air pollutants, causing severe air pollution and adverse health outcomes. In evaluating impacts on human health and climate, it is critical to understand the formation and emission processes of air pollutants from these combustion sources. Air pollutant emission factors (EFs) from indoor solid fuel combustion usually highly vary among different testing protocols, fuel-stove systems, sampling and analysis instruments, and environmental conditions. In this critical review, we focus on the latest developments in pollutant emission factor studies, with emphases on the difference between lab and field studies, fugitive emission quantification, and factors that contribute to variabilities in EFs. Field studies are expected to provide more realistic EFs for emission inventories since lab studies typically do not simulate real-world burning conditions well. However, the latter has considerable advantages in evaluating formation mechanisms and variational influencing factors in observed pollutant EFs. One main challenge in field emission measurement is the suitable emission sampling system. Reasons for the field and lab differences have yet to be fully elucidated, and operator behavior can have a significant impact on such differences. Fuel properties and stove designs affect emissions, and the variations are complexly affected by several factors. Stove classification is a challenge in the comparison of EF results from different studies. Lab- and field-based methods for quantifying fugitive emissions, as an important contributor to indoor air pollution, have been developed, and priority work is to develop a database covering different fuel-stove combinations. Studies on the dynamics of the combustion process and evolution of air pollutant formation and emissions are scarce, and these factors should be an important aspect of future work.

Air Quality in Southeast Brazil during COVID-19 Lockdown: A Combined Satellite and Ground-Based Data Analysis

With the current COVID-19 pandemic being spread all over the world, lockdown measures are being implemented, making air pollution levels go down in several countries. In this context, the air quality changes in the highly populated and trafficked Brazilian states of São Paulo (SP) and Rio de Janeiro (RJ) were addressed using a combination of satellite and ground-based daily data analysis. We explored nitrogen dioxide (NO2) and fine particulate matter (PM2.5) daily levels for the month of May from 2015–2020. Daily measurements of NO2 column concentrations from the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite were analyzed and decreases of 42% and 49.6% were found for SP and RJ, respectively, during the year 2020 compared to the 2015–2019 average. Besides NO2 column retrievals, ground-based data measured by the Brazilian States Environmental Institutions were analyzed and correlated with satellite retrievals. Correlation coefficients between year-to-year changes in satellite column and ground-based concentrations were 77% and 53% in SP and RJ, respectively. Ground-based data showed 13.3% and 18.8% decrease in NO2 levels for SP and RJ, respectively, in 2020 compared to 2019. In SP, no significant change in PM2.5 was observed in 2020 compared to 2019. To further isolate the effect of emissions reduction due to the lockdown, meteorological data and number of wildfire hotspots were analyzed. NO2 concentrations showed negative and positive correlations with wind speed and temperature, respectively. PM2.5 concentration distributions suggested an influence by the wildfires in the southeast region of the country. Synergistic analyses of satellite retrievals, surface level concentrations, and weather data provide a more complete picture of changes to pollutant levels.

Atmospheric particulate matter from an industrial area as a source of metal nanoparticle contamination in aquatic ecosystems

Air pollution legislation and control worldwide is based on the size of particulate matter (PM) to evaluate the effects on environmental and human health, in which the small diameter particles are considered more dangerous than larger sizes. This study investigates the composition, stability, size and dispersion of atmospheric settleable particulate matter (SePM) in an aqueous system. We aimed to interrogate the changes in the physical properties and characteristics that can contribute to increased metal uptake by aquatic biota. Samples collected in an area influenced by the steel and iron industry were separated into 8 fractions (425 to ≤10 μm) and analysed physically and chemically. Results from ICP-MS and X-ray showed that the PM composition was mainly hematite with 80% of Fe, followed by Al, Mn and Ti. Among 27 elements analysed we found 19 metals, showing emerging metallic contaminants such as Y, Zr, Sn, La, Ba and Bi. Scanning electron microscopy (SEM) showed that SePM fractions are formed by an agglomeration of nanoparticles. Furthermore, dynamic light scattering (DLS), zeta potential and nanoparticle tracking analysis (NTA) demonstrated that SPM were dissociated in water, forming nanoparticles smaller than 200 nm, which can also contribute to water pollution. This study highlights that SePM contamination may be substantially higher than expected under that allowed in atmospheric regulatory frameworks, thereby extending their negative effect to water bodies upon settling, which is an underexplored area of our knowledge. We therefore provide important insights for future investigations on safety regulations involving SePM in the environment, indicating the need to revise the role of SePM, not solely associated with air pollution but also considering their deleterious effects on water resources.

External Environmental Pollution as a Risk Factor for Asthma

Air pollution is a worrisome risk factor for global morbidity and mortality and plays a special role in many respiratory conditions. It contributes to around 8 million deaths/year, with outdoor exposure being responsible for more than 4.2 million deaths throughout the world, while more than 3.8 million die from situations related to indoor pollution. Pollutant agents induce several respiratory symptoms. In addition, there is a clear interference in numerous asthma outcomes, such as incidence, prevalence, hospital admission, visits to emergency departments, mortality, and asthma attacks, among others. The particulate matter group of pollutants includes coarse particles/PM₁₀, fine particles/PM_2.5, and ultrafine particles/PM_0.1. The gaseous components include ground-level ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide. The timing, load, and route of allergen exposure are other items affecting allergic disease phenotypes. The complex interaction between pollutant exposures and human host factors has an implication in the development and rise of asthma as a public health problem. However, there are hiatuses in the understanding of the pathways in this disease. The routes through which pollutants induce asthma are multiple, and include the epigenetic changes that occur in the respiratory tract microbiome, oxidative stress, and immune dysregulation. In addition, the expansion of the modern Westernized lifestyle, which is characterized by intense urbanization and more time spent indoors, resulted in greater exposure to polluted air. Another point to consider is the different role of the environment according to age groups. Children growing up in economically disadvantaged neighborhoods suffer more important negative health impacts. This narrative review highlights the principal polluting agents, their sources of emission, epidemiological findings, and mechanistic evidence that links environmental exposures to asthma.

Assessment of biomass demineralization on gasification: From experimental investigation, mechanism to potential application

Considering the advantages (e.g. agglomeration mitigation) and disadvantages (e.g. inorganic species catalysis removal) of biomass demineralization, it is valuable to investigate its effects on gasification performance, thus assessing its necessity prior to performing gasification. To accomplish this, corn straw (CS) was demineralized to different degrees with H₂O and HCl, respectively. H₂O and HCl demineralization behaved different abilities to inorganic species removal. Cellulose and hemicelluloses content decreased, while lignin content increased, especially with HCl demineralization. The experiments were investigated by using a bench-scale downdraft fixed-bed gasifier at 600-800 °C and were further analyzed via thermogravimetric coupled with Fourier transform infrared spectrometry. Demineralization demonstrated a positive effect on gasification at lower temperatures (600-700 °C) for a dominant effect of lignin content and an insignificant effect of inorganic species removal. However, the catalysis of inorganic species increased as the temperature increased, resulting in the highest H₂ (11.30 vol%) and CO (16.02 vol%) production of raw CS compared to demineralized CS at 800 °C. Inorganic species had a dual positive effect on CO generation, promoting both CO₂ and char generation leading to a higher CO yield following Boundouard reaction, and increasing the formation of active intermediates thus producing more CO. These effects enhanced when the gasification temperature increased. Additionally, inorganic species catalyzed the aromatic rings rearrangement to generate more H₂O, thus driving the endothermic Primary water-gas to produce H₂. This was also positively correlated with gasification temperature. Therefore, raw CS demonstrated higher H₂ and CO production than demineralized CS at a higher gasification temperature. Moreover, the promotion effect of inorganic species on thermal devolatilization of methoxyl groups and Methanation reaction led to the higher CH₄ production of raw CS. This research clarifies the effects of biomass demineralization on its gasification and suggests the potential application.

Experimental Study on Hydrothermal Carbonization of Lignocellulosic Biomass with Magnesium Chloride for Solid Fuel Production

The effect of magnesium chloride as an additive of hydrothermal carbonization (HTC) of lignocellulosic biomass (Pinus radiata sawdust) was studied. The HTC tests were carried out at fixed conditions of temperature and residence time of 220 °C and 1 h, respectively, and varying the dose of magnesium chloride in the range 0.0–1.0 g MgCl2/g biomass. The carbonized product (hydrochar) was tested in order to determine its calorific value (HHV) while using PARR 6100 calorimeter, mass yield by gravimetry, elemental analysis using a LECO TruSpec elemental analyzer, volatile matter content, and ash content were obtained by standardized procedures using suitable ovens for it. The results show that using a dose of 0.75 g MgCl2/g biomass results in an impact on the mass yield that was almost equal to change operating conditions from 220 to 270 °C and from 0.5 to 1 h, without additive. Likewise, the calorific value increases by 33% for this additive dose, resulting in an energy yield of 68%, thus generating a solid fuel of prominent characteristics.

Validation of PM2.5 model particle through physicochemical evaluation and atherosclerotic plaque formation in ApoE-/- mice

PM_2.5 particles are regarded as prominent risk factors that contribute to the development of atherosclerosis. However, the composition of PM_2.5 is rather complicated. This study aimed to provide a model particle that simulates the behavior of actual PM_2.5, for subsequent use in exploring mechanisms and major complications arising from PM_2.5. To establish model particles of PM_2.5, a series of monodisperse SiO₂ microspheres with different average grain diameters were mixed according to the size distribution of actual PM_2.5. The organic carbon (OC) was removed from PM_2.5 and coated onto the SiO₂ model particle, to formulate simulant PM_2.5. Results showed that the size distribution of the model particle was highly approximate to that of the PM_2.5 core. The polycyclic aromatic hydrocarbon (PAHs) composition profile of the simulated PM_2.5 were approximate to PM_2.5, and loading efficiency was approximately 80%-120%. Furthermore, compared to the control, SiO₂-only model particle had negligible cytotoxicity on cell viability and oxidative stress of HUVECs, and marginal effect on the lipid metabolism and atherosclerotic plaque formation in ApoE^-/- mice. In contrast, simulated PM_2.5 exhibited similar cytotoxic and detrimental effects on lipid metabolism and atherosclerotic plaque formation with actual PM_2.5. Traffic-related PM_2.5 had negative effects on endothelial function and led to the formation of atherosclerosis via oxidative stress. The simulated PM_2.5 simulated the outcomes of actual PM_2.5 exposure. Here, we show that SiO₂ particle model cores coated with OC could significantly assist in the evaluation of the effects of specific organic compositions bound on PM_2.5, specifically in the context of environmental health and safety.

Estimation of Energy and Emissions Properties of Waste from Various Species of Mint in the Herbal Products Industry

The paper presents the results of research on the physicochemical properties of plant biomass consisting of four mint species, these being Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’, Mentha × rotundifolia L., Mentha spicata L., and Mentha crispa L. The research conducted consisted of the technical analysis of biofuels—determining the heat of combustion and the calorific value of the material under study, and the content of ash, volatile compounds, and humidity. In addition, elemental analysis was carried out for the biomass under study by determining the content of carbon, hydrogen, nitrogen, and sulfur. The research demonstrated that Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’ had the highest energy potential with a gross calorific value of 16.96 MJ·kg−1, and a net calorific value of 15.60 MJ·kg−1. Among the tested materials, Mentha × rotundifolia L. had the lowest content of ash at 7.23%, nitrogen at 0.23%, and sulfur at 0.03%, and at the same time had the highest content of volatile fraction at 70.36%. When compared to hard coal, the estimated emission factors indicated a CO reduction of 29–32%, CO2 reduction of 28–31%, NOx reduction of 40–80%, SO2 reduction of 92–98%, and dust reduction of 45–61%, depending on the type of biomass used.

Combustion behavior, emission characteristics of SO2, SO3 and NO, and in situ control of SO2 and NO during the co-combustion of anthracite and dried sawdust sludge

The combustion behaviors of anthracite and dried sawmill sludge (DSS) were studied using thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). DSS was found to be a promoter for anthracite combustion, the addition of DSS in anthracite decreased the burnout temperature and time. But DSS caused the rapid releases of SO₂ and NO in the initial combustion stage. In overall, the increasing of DSS significantly decreased the emission factor of SO₂ from 13.42 ± 1.80 to 0.31 ± 0.08 g/kg; while the emission factor of NO was not obviously changed and stable at 0.7-0.8 g/kg in all cases. The oxygen-rich atmosphere was helpful for the rapid and sufficient combustion of blend; the oxygen-lean atmosphere delayed the combustion process and slowed down the releases of SO₂ and NO. The increasing combustion temperature improved the anthracite combustion, and the emission factors of SO₂ and NO were all increased with the temperature increasing. 900 °C was found to be the best combustion temperature for NO generation. SO₃ was detected in the combustion of anthracite under 21% and 30% of O₂. Two promising ways for control of SO₂ and NO were provided: 1) urea-fuel mixture combustion combined with the post-combustion wet absorption by Na₂CO₃; 2) post-combustion wet absorption by NaClO/Na₂CO₃. The removal efficiencies of SO₂ and NO could reach 100% and over 95% respectively. The removal products were determined as sulfate, sulfite and nitrate by IC, with no toxic byproducts being produced.

Sustainable Renewable Energy by Means of Using Residual Forest Biomass

The substitution of energy based on fossil fuel by bioenergy could be an effective solution to reduce external energy dependency, thereby promoting sustainable development. This article details a study of the use of biomass residues produced in the forestry sector as a consequence of field operations of the two predominant forest species (Pinus radiata D. Don and Ecualyptus globulus Labill) of Biscay (Spain). The potential of forest residues is estimated to be 66,600 dry Mg year − 1 . These residues would provide 1307 TJ year − 1 . Energy parameters, ultimate and proximate analyses, and the level of emissions of the forest residues are performed in order to estimate their characteristics as fuel. The research done has shown very similar values in terms of the net calorific value of the residues of P. radiata (19.45 MJ kg − 1 ) and E. globulus (19.48 MJ kg − 1 ). The determined emission factors indicate a reduction in gas emissions: CO (23–25%), CO 2 (22–25%), SO 2 (87–91%) and dust (11–38%) and an increase of 11–37% in NO x compared to hard coal. Estimation of the emission factors of the residual biomass allows the environmental impacts, that are potentially produced by biofuel, to be estimated.

Emission factors of atmospheric and climatic pollutants from crop residues burning

Biomass burning is a common agricultural practice, because it allows elimination of postharvesting residues; nevertheless, it involves an inefficient combustion process that generates atmospheric pollutants emission, which has implications on health and climate change. This work focuses on the estimation of emission factors (EFs) of PM_2.5, PM₁₀, organic carbon (OC), elemental carbon (EC), carbon monoxide (CO), carbon dioxide (CO₂), and methane (CH₄) of residues from burning alfalfa, barley, beans, cotton, maize, rice, sorghum, and wheat in Mexico. Chemical characteristics of the residues were determined to establish their relationship with EFs, as well as with the modified combustion efficiency (MCE). Essays were carried out in an open combustion chamber with isokinetic sampling, following modified EPA 201-A method. EFs did not present statistical differences among different varieties of the same crop, but were statistically different among different crops, showing that generic values of EFs for all the agricultural residues can introduce significant uncertainties when used for climatic and atmospheric pollutant inventories. EFs of PM_2.5 ranged from 1.19 to 11.30 g kg^-1, and of PM₁₀ from 1.77 to 21.56 g kg^-1. EFs of EC correlated with lignin content, whereas EFs of OC correlated inversely with carbon content. EFs of EC and OC in PM_2.5 ranged from 0.15 to 0.41 g kg^-1 and from 0.33 to 5.29 g kg^-1, respectively, and in PM₁₀, from 0.17 to 0.43 g kg^-1 and from 0.54 to 11.06 g kg^-1. CO₂ represented the largest gaseous emissions volume with 1053.35-1850.82 g kg^-1, whereas the lowest was CH₄ with 1.61-5.59 g kg^-1. CO ranged from 28.85 to 155.71 g kg^-1, correlating inversely with carbon content and MCE. EFs were used to calculate emissions from eight agricultural residues burning in the country during 2016, to know the potential mitigation of climatic and atmospheric pollutants, provided this practice was banned.

IMPLICATIONS

The emission factors of particles, short-lived climatic pollutants, and atmospheric pollutants from the crop residues burning of eight agricultural wastes crops, determined in this study using a standardized method, provides better knowledge of the emissions of those species in Latin America and other developing countries, and can be used as inputs in air quality models and climatic studies. The EFs will allow the development of more accurate inventories of aerosols and gaseous pollutants, which will lead to the design of effective mitigation strategies and planning processes for sustainable agriculture.

Emission factors from different burning stages of agriculture wastes in Mexico

Open-air burning of agricultural wastes from crops like corn, rice, sorghum, sugar cane, and wheat is common practice in Mexico, which in spite limiting regulations, is the method to eliminate such wastes, to clear the land for further harvesting, to control grasses, weeds, insects, and pests, and to facilitate nutrient absorption. However, this practice generates air pollution and contributes to the greenhouse effect. Burning of straws derived from the said crops was emulated in a controlled combustion chamber, hence determining emission factors for particles, black carbon, carbon dioxide, carbon monoxide, and nitric oxide throughout the process, which comprised three apparent stages: pre-ignition, flaming, and smoldering. In all cases, maximum particle concentrations were observed during the flaming stage, although the maximum final contributions to the particle emission factors corresponded to the smoldering stage. The comparison between particle size distributions (from laser spectrometer) and black carbon (from an aethalometer) confirmed that finest particles were emitted mainly during the flaming stage. Carbon dioxide emissions were also highest during the flaming stage whereas those of carbon monoxide were highest during the smoldering stage. Comparing the emission factors for each straw type with their chemical analyses (elemental, proximate, and biochemical), some correlations were found between lignin content and particle emissions and either particle emissions or duration of the pre-ignition stage. High ash or lignin containing-straw slowed down the pre-ignition and flaming stages, thus favoring CO oxidation to CO₂.