Overlooked CO2 emissions induced by air pollution control devices in coal-fired power plants

Comparison of PAH mass emissions and their toxicity-weighted trends in China, 2000-2022

Polycyclic aromatic hydrocarbons (PAHs) emissions are often used as direct evidence for subsequent environmental monitoring, governance, and policy-making. However, the toxicity among individual PAH varies significantly, causing their toxicity-based risk to be overlooked. The analysis revealed that total PAH emissions (EΣPAHs) has peaked in 2007 (i.e., 1.1 × 105 t), then declined to 2022 (i.e., 7.4 × 104 t) in China. However, the toxicity-weighted PAH emissions (EΣTEQ) has not decreased, because the emissions of high molecular weight PAH (EΣHPAHs) with high toxicity has not decreased, although the emissions of low molecular weight PAH (EΣLPAHs) with low toxicity has decreased significantly. It was verified that the trend of variation in PAH emissions is comprehensively determined by the decrease in biomass and increase in fossil fuel consumption. The decline in EΣLPAHs from biomass burning exceeded emission increases attributable to fossil fuel combustion, driving an overall reduction in total LPAHs post-2007 of China. In contrast, EΣHPAHs exhibited temporal variability after 2007, as emission reductions from biomass burning were offset by comparable increases from fossil fuel. Despite efforts to reduce emissions of conventional atmospheric pollutants, EΣTEQ have not decreased due to the rising fossil fuel consumption and limited pollution control efficiency on EΣHPAHs. The findings addressed the gap between PAH mass emissions and their toxicity-weighted trends, which enabled us to pay attention to the variation of EΣTEQ for accurate risk management to any region with shifting PAH source profiles. Moreover, emphasis should be placed on transitioning fossil fuel consumption to clean energy and implementing effective measures to reduce EΣHPAHs in flue gas, such as adsorption and degradation.

Identifying Key Sources for Air Pollution and CO2 Emission Co-control in China

China is confronting the dual challenges of air pollution and climate change, mandating the co-control of air pollutants and CO2 emissions from their shared sources. Here we identify key sources for co-control that prioritize the mitigation of PM2.5-related health burdens, given the homogeneous impacts of CO2 emissions from various sources. By applying an integrated analysis framework that consists of a detailed emission inventory, a chemical transport model, a multisource fused dataset, and epidemiological concentration-response functions, we systematically evaluate the contribution of emissions from 390 sources (30 provinces and 13 socioeconomic sectors) to PM2.5-related health impacts and CO2 emissions, as well as the marginal health benefits of CO2 abatement across China. The estimated source-specific contributions exhibit substantial disparities, with the marginal benefits varying by 3 orders of magnitude. The rural residential, transportation, metal, and power and heating sectors emerge as pivotal sources for co-control, with regard to their relatively large marginal benefits or the sectoral total benefits. In addition, populous and heavily industrialized provinces such as Shandong and Henan are identified as the key regions for co-control. Our study highlights the significance of incorporating health benefits into formulating air pollution and carbon co-control strategies for improving the overall social welfare.

Enhancing photocatalytic CO2 reduction with TiO2-based materials: Strategies, mechanisms, challenges, and perspectives

The concentration of atmospheric CO2 has exceeded 400 ppm, surpassing its natural variability and raising concerns about uncontrollable shifts in the carbon cycle, leading to significant climate and environmental impacts. A promising method to balance carbon levels and mitigate atmospheric CO2 rise is through photocatalytic CO2 reduction. Titanium dioxide (TiO2), renowned for its affordability, stability, availability, and eco-friendliness, stands out as an exemplary catalyst in photocatalytic CO2 reduction. Various strategies have been proposed to modify TiO2 for photocatalytic CO2 reduction and improve catalytic activity and product selectivity. However, few studies have systematically summarized these strategies and analyzed their advantages, disadvantages, and current progress. Here, we comprehensively review recent advancements in TiO2 engineering, focusing on crystal engineering, interface design, and reactive site construction to enhance photocatalytic efficiency and product selectivity. We discuss how modifications in TiO2's optical characteristics, carrier migration, and active site design have led to varied and selective CO2 reduction products. These enhancements are thoroughly analyzed through experimental data and theoretical calculations. Additionally, we identify current challenges and suggest future research directions, emphasizing the role of TiO2-based materials in understanding photocatalytic CO2 reduction mechanisms and in designing effective catalysts. This review is expected to contribute to the global pursuit of carbon neutrality by providing foundational insights into the mechanisms of photocatalytic CO2 reduction with TiO2-based materials and guiding the development of efficient photocatalysts.

Evaluation of pulse-jet baghouse dust collectors' contribution to CO2 emissions

Dust cleaning systems are mandatory for use almost in any manufacturing process. Their market size is expected at US$10.77 billion by 2030 growing from US$7.28 billion in 2022. Removing dust particles is the main purpose of these systems and they make an invaluable contribution to environmental safety. However, while cleaning the air from solid particles, industrial pulse-jet baghouse collectors have an additional impact on the environment that usually is not considered. An analysis of energy consumption at the manufacturing and operation stages of the baghouse dust collectors allows for the evaluation of CO2 emissions. The analysis shows that, given the current state of affairs in the industry, by 2030 manufacturing and operation of baghouse dust collectors over the world will emit 70+ million tons of carbon dioxide additionally to the levels of 2021. To reduce the CO2-related environmental impact of industrial pulse-jet baghouse collectors, among all scientific and technical measures, it is recommended to simply scale up the dust collection system, which involves replacing several low-capacity collectors with one general-capacity collector within one industrial enterprise. This allows for a reduction in energy consumption at the collector manufacturing stage from 3 to 10 times and also ensures a significant reduction in operation energy consumption of the dust collector during its service life.

Combustion properties and pollutant analysis of coal-blended bio-heavy oil fuel

Excessive carbon-dioxide emissions drive global climate change and environmental challenges. Integrating renewable biomass fuels with coal in power units is crucial for achieving low-carbon emission reductions. Coal blending with bio-heavy oil enhances the combustion calorific value of the fuel, improves combustion characteristics, and decreases pollutant emissions. This study found that bio-heavy oil with low sulfur (0.073%), low nitrogen (0.18%), low ash, and high oxygen (11.005%) content exhibits excellent fuel performance, which can be attributed to the abundant oxygen-containing functional groups (such as C[double bond, length as m-dash]O) in the alcohols, aldehydes, and ketones present in bio-heavy oil. Additionally, the residual moisture in coal-blended bio-heavy oil reduces the fuel's calorific value. The calorific value increases with a higher proportion of blended bio-heavy oil (28.1, 28.9, 32.1, 34.7, 40.6 MJ kg-1). Experiments on combustion flame shooting reveal that the combustion time of bio-heavy oils is significantly shorter than that of coal. As the proportion of blended bio-heavy oil increases, the flame height increases. Coal blending with bio-heavy oil involves three stages: water evaporation, volatile-matter decomposition, fixed-carbon combustion and mineral decomposition. This advances the combustion process and improves coal's ignition performance. Furthermore, the amount of gaseous pollutants (sulfur dioxide and nitrogen dioxide) in coal mixed with bio-heavy oil is relatively low, which is in alignment with the green environmental protection guidelines. The blending of coal with biomass fuel holds significant practical and strategic importance for developing high-efficiency, low-carbon, coal power units.