Search

Hydraulic fracturing technologies have been frequently utilized in the oil and gas industry as exploration and development efforts have progressed, resulting in a significant increase in the extraction of natural gas and petroleum from low-permeability reservoirs. However, hydraulic fracturing requires a large amount of freshwater, and the process results in the production of large volumes of flowback water along with natural gas. In this study, three tight sandstone gas wells were fractured in the Sulige gasfield (China), and a total of 103 flowback fluid samples were collected. The hydrochemical characteristics, water quality and sources of hydrochemical components in the flowback fluid were discussed. The results show that the flowback fluid is characterized by high salinity (Total dissolved solids (TDS) up to 38,268 mg/L, Cl− up to 24,000 mg/L), high concentrations of metal ions (e.g., Fe, Sr2+, Ba2+) and high chemical oxygen demand (COD). The flowback fluid is a complex mixture of fracturing fluid and formation water, and its composition is impacted by water–rock interactions that occur during hydraulic fracturing. The major contaminants include COD, Fe, Ba2+, Cl−, Mn and pH, which constitute a high risk of environmental pollution. Meanwhile, chemical elements such as K, Ba and Sr are unusually enriched in the flowback fluid, which has an excellent potential for recycle of chemical elements. The Sulige gasfield's flowback fluid recovery methods and treatment scenarios were discussed, taking into consideration the pollution and resource characteristics of the flowback fluid. Options for dealing with the flowback fluid include deep well reinjection, reuse for making up fracturing fluid, recycling of chemical elements and diverse reuse of flowback water. This research offers guidance for managing the fracturing flowback fluid in unconventional oil and gas fields. [ABSTRACT FROM AUTHOR]

Copyright of China Textile Leader is the property of China Textile Information Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Gasification-based chemical recycling exhibits promise to support China's decarbonization efforts. • Compared to waste incineration, chemical recycling is associated with a higher emission reduction potential. • China's energy transition will further increase the emission reduction potential of chemical recycling. • The decarbonization potential of gasification-based chemical recycling is associated with increased economic costs. • Findings support policy and industry decision-makers in transforming China's waste management systems. The waste and chemical sectors contribute significantly to China's carbon footprint. Linking these sectors via chemical recycling could contribute to achieving China's goal to decarbonize via defossilization. This study comparatively evaluates the decarbonization and economic potential of gasification-based chemical recycling of municipal solid waste against conventional waste treatment (i.e., landfilling and waste incineration). Results from Life Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) indicate that not only does waste gasification exhibit higher global warming reduction potential than conventional treatment (e.g., -70 kg CO2-eq. per tonne of waste compared to currently expanding waste incineration), but this potential will also increase as China's energy mix becomes increasingly renewable (i.e., -320 kg CO2-eq). However, this decarbonization potential will also be associated with higher plant investments (+50 %) and a lower net present value (-20 %). Insights from this study enrich the Chinese discourse on sustainable waste management practices across scientific, regulatory, and industrial dimensions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Lead salt heat stabilizers (LHSs) are common toxic and harmful additive used in plastics. • Construction sector and landfills accumulates 88.1 % in-use stocks and 48.3 % waste stocks of LHSs, respectively. • The future scrapping of in-use stocks and the recycling of LHSs with plastics will delay the lead-free plastics process. • Lead-free plastics require the early prohibition of LHSs use in plastics and LHSs circulation in plastic recycling. • Scientific estimation of emissions is the basis for evaluating the ecological and human health risks posed by LHSs. The use of lead salt heat stabilizers (LHSs) in plastics are restricted or even prohibited owing to their high toxicity. However, little information is available on its industrial metabolism. A dynamic material flow analysis of LHSs indicates that China consumed 2952 kt LHSs between 1958 and 2020. Moreover, at present, 1020 kt of these is being used in polyvinyl chloride (PVC) products, 1007 kt is in landfills, and 681 kt is in the environment. For China to realize lead-free primary plastics by 2040, 2050, and 2060, the LHSs consumption should be reduced by at least 13 %, 10 %, and 9 % annually, respectively. Certain LHSs would gain new life with PVC recycling. Therefore, approximately 30 years would be required for LHSs to disappear completely after their use is stopped. With improvements in the plastic recycling rate, it is necessary to use chemical recycling and other methods to separate the hazardous additives such as LHSs and reduce the circulation of toxic substances. [Display omitted] [ABSTRACT FROM AUTHOR]

Coking plants in China generate a substantial amount of volatile organic compounds (VOCs). The emission factors (EFs) of VOCs from coking plants are not well known, and thus, this study characterized the VOCs in the emissions from four coking plants in Shanxi, China. The EFs of VOCs from different stages of the coking process were calculated, and coal charging exhibited the highest EFs of VOCs, followed by the flue gases from combustion of coke oven gas, wastewater treatment, coke pushing and chemical byproduct recycling. The VOCs in emissions differed by coking process. Alkanes, aromatics and alkenes were the main VOCs emitted during the coking, wastewater treatment and chemical byproduct recycling processes, respectively. To effectively control the contribution of VOCs from coking processes to secondary organic aerosols and ozone formation, attention should be given to wastewater treatment and coal loading processes. The mean annual weight of VOCs emitted from coking plants in China from 2019 to 2021 was estimated to be 32.91 Gg with coking, chemical byproduct recycling, and wastewater treatment processes accounting for 91.34%, 7.85%, and 0.80% of total VOCs, respectively. An uneven spatial distribution of VOCs emissions in China was identified, with Shanxi, Shaanxi, Hebei, Inner Mongolia and Shandong being the largest contributors. [Display omitted] • The measured emission factors of VOCs from coal charging is the highest. • VOCs emission factor reached 70.18 g/t coke for coking industries in Shanxi. • Aromatics were the main VOCs emitted from coking wastewater treatment. • An uneven spatial distribution of VOCs emissions within China was identified. [ABSTRACT FROM AUTHOR]

• The environmental impacts of three PV waste treatment technologies were assessed. • Recycling PV module wastes brings significant environmental benefits. • All the three PV recycling technologies are expensive in China currently. • Pathways with low environmental burdens and economic costs were identified. China will face great challenges related to PV waste in the coming decades. Mechanical recycling (MR), chemical recycling (CR), and thermal recycling (TR) are widely regarded as future technologies for PV recycling; however, knowledge about their costs and benefits remains unexplored in China. In this study, the costs and benefits of these technologies are comprehensively assessed and compared using a life cycle assessment (LCA). The results showed that MR, CR, and TR had the smallest amounts of life-cycle energy use (−28,949 MJ/ton), industrial water use (−65,069 kg/ton), and global warming potential (−5525 kg CO2 eq/ton), respectively. To date, cost-benefit analyses have demonstrated PV recycling was expensive. Overall, all three PV-recycling technologies show superior environmental and economic performance compared with landfilling. Scenario analysis showed that improvements in technology, expansion of the recycling scale, reducing transport distances, and subsidization are all effective measures for enhancing the total benefits of PV waste recycling. [Display omitted] [ABSTRACT FROM AUTHOR]