U.S. plastic waste exports: A state-by-state analysis pre- and post-China import ban.

This study analyzes the regional implications of China's 2017 import ban on plastic waste by examining U.S. census data. A statistically significant decrease in total U.S. plastic waste exports was found, dropping from about 1.4 million tons to 0.6 million tons in the post-ban period. California remained the top exporter, throughout both pre- and post-ban periods, while South Carolina exhibited the highest per capita exports. Malaysia emerged as the largest importer of U.S. plastic waste, followed by Vietnam, Indonesia, and Thailand. The ban also led to a change in the composition of the exported plastic waste. Ethylene polymers increased from 32.6% of total exports in the pre-ban period to 46.9% in the post-ban period. Other plastics (vinyl chloride polymers, styrene polymers, and for plastics not elsewhere specified or included) decreased from 67.4% of total exports in the pre-ban period to 53.1% in the post-ban period. Moreover, we found that exporting plastic waste has significant environmental and human health impacts. For example, the Global Warming Potential (GWP) decreased from 20 million tons CO2-eq in the scenario where 100% of plastics are exported, or 25 million tons exported from the U.S. since 2002, to -11.1 million tons CO2-eq in the scenario where 100% of plastics are treated domestically. Transportation exacerbates these impacts for exported waste scenarios, increasing to 5.4 million tons CO2-eq when plastics are exported by ship while decreasing to 0.9 million tons CO2-eq for domestic treatment. Although exporting plastic waste is initially cost-effective, our study highlights that investing in domestic waste management can yield significant long-term benefits, considering the environmental and public health impacts. Therefore, it is crucial to prioritize context-specific solutions to address the challenges of the evolving global plastic waste landscape.

Review on fate of chlorine during thermal processing of solid wastes.

Chlorine (Cl) is extensively present in solid wastes, causing significant problems during the thermal conversion of waste to energy or fuels, by combustion, gasification or pyrolysis. This paper introduces the analytical methods for determining the Cl content in solid materials and presents the concentrations of Cl in various types of wastes, as reported in literature. Then, it provides a comprehensive analysis on the Cl emission behavior and Cl species formed during the thermal processing of the inorganic and organic Cl sources. The challenges resulted from the reactions between the formed Cl species and the ferrous metals, the heavy metals and the organic matters are summarized and discussed, e.g., high temperature corrosion, heavy metal evaporation and dioxin formation. The quality degradation of products (oil, char and syngas) by Cl is analyzed. Finally, the available controlling methods of Cl emission, including pre-treatment (water washing, sorting, microwave irradiation and stepwise pyrolysis) and in-furnace (absorbents, co-treatment and catalysts) methods are assessed.

Performance of structural concrete using Waste-to-Energy (WTE) combined ash.

In the U.S., about 27 million metric tons of municipal solid waste are used as fuel in Waste-to-Energy (WTE) power plants, generating about seven million tons of mixed bottom ash and fly ash (combined ash) annually, which are disposed of in landfills after metal separation. This study assessed the effect of using combined ash as a substitute of mined stone aggregates on the mechanical properties and leachability of cement mortar and concrete. The as-received combined ash was separated into three fractions: fine (<2 mm), medium (2-9.5 mm), and coarse (9.5-25 mm). The substitution of up to 100% of stone aggregate by the coarse and medium fractions of combined ash produced concrete with compressive strength exceeding 28 MPa after 28 days of curing. Similar results were obtained when the fine combined ash was used as a sand substitute, at 10 wt%, in mortar. The concrete specimens were subjected to several days of curing and mechanical testing. The results were comparable to the properties of commercial concrete products. The mechanical test results were supplemented by XRD and SEM analysis, and leachability tests by EPA Method 1313 showed that the optimal concrete products effectively immobilized the heavy metals in the combined ash.