Characterizing dynamic relationships between burning rate and pollutant emission rates in a forced-draft gasifier stove consuming biomass pellet fuels

Exploring efficient strategies for air quality improvement in China based on its regional characteristics and interannual evolution of PM2.5 pollution

Fine particulate matter (PM2.5) harms human health and hinders normal human life. Considering the serious complexity and obvious regional characteristics of PM2.5 pollution, it is urgent to fill in the comprehensive overview of regional characteristics and interannual evolution of PM2.5. This review studied the PM2.5 pollution in six typical areas between 2014 and 2022 based on the data published by the Chinese government and nearly 120 relevant literature. We analyzed and compared the characteristics of interannual and quarterly changes of PM2.5 concentration. The Beijing-Tianjin-Hebei region (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) made remarkable progress in improving PM2.5 pollution, while Fenwei Plain (FWP), Sichuan Basin (SCB) and Northeast Plain (NEP) were slightly inferior mainly due to the relatively lower level of economic development. It was found that the annual average PM2.5 concentration change versus year curves in the three areas with better pollution control conditions can be merged into a smooth curve. Importantly, this can be fitted for the accurate evaluation of each area and provide reliable prediction of its future evolution. In addition, we analyzed the factors affecting the PM2.5 in each area and summarize the causes of air pollution in China. They included primary emission, secondary generation, regional transmission, as well as unfavorable air dispersion conditions. We also suggested that the PM2.5 pollution control should target specific industries and periods, and further research need to be carried out on the process of secondary production. The results provided useful assistance such as effect prediction and strategy guidance for PM2.5 pollution control in Chinese backward areas.

Composition of inorganic elements in fine particulate matter emitted during surface fire in relation to moisture content of forest floor combustibles

The moisture content of combustible material on the forest floor is constantly changing due to environmental factors, which have a direct impact on the composition and emission intensity of particulate matter released during fire. In this study, an indoor biomass combustion analysis device was used to analyze the emission characteristics of fine particulate matter (PM_2.5) from combustion of herbaceous combustible materials with different moisture contents (0%, 15%, and 30%). The composition of inorganic elements in PM_2.5 (Zn, K, Mg, Ca, and other 13 measurable elements) were determined by inductively coupled plasma-mass spectrometer (ICP-MS). The results showed that the PM_2.5 emission factor increased significantly with the increase of moisture content of combustible materials in the range of 11.63 ± 0.55 for dry samples to 36.71 ± 1.21 g/kg for samples with 30% moisture content. The main elemental components of PM_2.5 were K, Zn, Ca, Mg, and Na and K, Ca, Mg, and Na emission factors increased with the increase of moisture content of combustibles. The proportion of macronutrients in PM_2.5 released by combustion of each herb increased as the moisture content increased, but the proportion of trace elements gradually decreased. There was a good correlation between elemental composition of PM_2.5 and that of herbaceous combustibles. The results provide evidence that the moisture content of combustible materials has a significant effect on the emission of inorganic elements in particulate matter, and hence cautions should be exercised during fuel reduction treatments, such as early prescribed fire.

An experimental study on the development of multipurpose biomass burner for cooking stove and thermal generator for household application

The present study proposes a novel concept of a solid biomass burner for household applications. The designed biomass stove is a multipurpose burner that can be used as a cooking stove and thermal generator. It works as a basic model of a biomass cooking stove and is coupled with a coil heat exchanger for thermal generation. The experimental evaluation is conducted by using the time-to-boil (TTB) method to measure the effective energy that can be harnessed from the combustion process. It shows that the maximum temperature outlet from the coil heat exchanger is 62.2 °C. The effective energy uptake for the coil heat exchanger is 41.9%, whereas the overall energy uptake, including the kettle, is obtained by more than 50%. Therefore, the proposed model can improve the efficiency of solid biomass burners for household ware.

Biofuel characteristics of non-charred briquettes from dried fecal sludge blended with food market waste: Suggesting a waste-to-biofuel enterprise as a win-win strategy to solve energy and sanitation problems in slums settlements

This study explored the production and evaluation of briquettes made from dried fecal sludge mixed with fresh food waste as a dual strategy to solve energy poverty and poor sanitation problems in Ugandan slums. Cylindrical briquettes measuring 82 mm height by 76 mm diameter were produced from dried fecal sludge (FS) alone, and FS mixed separately with pineapple peels (FS + PP), charcoal fines (FS + CD), and bean husks (FS + BH) in a mix ratio of 50% FS: 50% biomass (wt/wt basis) using red soil as the binder. Physiochemical characteristics and fuel thermal efficiency of the briquettes were tested following ASTM standards and were compared to wood-derived charcoal and commonly traded briquettes on market in Uganda. The average moisture content was 5.1%. Bulk density was highest in FS briquettes (1.12 g/cm³) and lowest in FS + BH (0.847 g/cm³). Volatile matter (VM) was highest in FS + PP (39%) and lowest in FS alone (25.7%). The average ash content was 30.4%. FS + PP had the highest calorific value (17.92 MJ/kg) while FS alone had the lowest (6.19 MJ/kg). The highest burning rate was recorded in FS + CD briquettes (8 g/min) and was lowest in FS + PP (4 g/min). Based on the calculated burning rates and calorific values, the economic advantage calculations implied that blending one ton of dry FS with one ton of dry pineapple peels for fuel briquettes, and their use as a substitute could save consumers about USD 620 per ton of wood charcoal foregone.

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.

Field-based measurements of major air pollutant emissions from typical porcelain kiln in China

China has been famous for its porcelains for millennia, and the combustion processes of porcelain production emit substantial amounts of air pollutants, which have not been well understood. This study provided firsthand data of air pollutant emissions from biomass porcelain kilns. The emission factor of PM_2.5 was 0.95 ± 1.23 g/kg during the entire combustion cycle, lower than that of biomass burning in residential stoves and coal burning in brick kilns, attributed to the removal effects of the long-distance transport in dragon kilns. The temporal trend of particle pollutants, including particulate matters (PMs) and particulate polycyclic aromatic hydrocarbons (PAHs) (low at ignition phase and high at the end) again indicated the removal effects of the special structure, while gaseous pollutants, such as gaseous PAHs, exhibited the opposite result. The GWC₁₀₀ was estimated as 1.4 × 10⁶ and 0.5 × 10⁶ kg CO₂e/yr for the scenarios in which 50% and 100% of the wood was renewable, respectively. The GWC₁₀₀ of dragon kilns is nearly equal to that of 745 households using wood-fueled stoves. These results indicate the necessity of pollution controls for biomass porcelain kilns to estimate the emission inventory and climate change.

Biomass molded fuel in China: Current status, policies and suggestions

China is an agricultural country, approximately producing more than 1000 million tons of crop straw in 2018. The utilization of straw as energy can replace fossil fuels, protect environment and guarantee energy security. Biomass fuel has been regarded as renewable energy with the characteristics of carbon-neutral, and low emissions of nitrogen oxides and sulfur dioxide. Biomass molded fuel (BMF), a major type of biomass fuel, has attracted particular attention. Currently, the BMF industry in China develops slowly. To achieve the rapid and healthy development of the industry, in this paper, a three-part standard system as fuel side, production and combustion equipment side and pollutant emission side is proposed to regulate the BMF market. Simultaneously, a policy system consisting of legislation, development plans and incentive measures also is introduced to maintain policy consistency and continuity.