China is the largest producer and consumer of calcium carbide in the world. The calcium carbide industry is an indispensable industry to support the basic life of people. The huge production capacity of calcium carbide is accompanied by a large number of solid waste carbide slag. Due to the immature treatment technology of carbide slag, a large number of carbide slag are stacked on-site, resulting in land occupation, air-drying, easy take-off ash, and pollution of the environment and water resources. In China, calcium carbide is mainly used to produce acetylene and further utilized, 80% of which is used to produce polyvinyl chloride (PVC). A large amount of carbide slag is not used, while only a small part is used in the traditional building materials industry, flue gas desulfurization, sewage treatment, etc., however, the economic benefits are poor. Therefore, converting the solid waste carbide slag produced by the calcium carbide industry into high value-added CaCO3, CaCl2, CaSO4 whiskers, etc. has become a potential way to expand the development field of the calcium carbide industry and is environmentally friendly. This paper focuses on summarizing the traditional and emerging high value-added utilization technologies of carbide slag, and then introduces the application research of carbide slag in carbon emission reduction. Finally, the defects of these technologies are summarized and further research directions are prospected. This study provides basic guidance for the diversified development of efficient resource utilization of carbide slag.

This study investigated the removal of antibiotics and antibiotic resistance genes from sewage sludge by using fly ash (FA)-based in situ advanced anaerobic digestion (AAD) under mesophilic conditions. Five antibiotics (sulfadiazine, sulfamethoxazole, ofloxacin, tetracycline, and roxithromycin) and 11 corresponding antibiotic resistance genes (Ib-cr, qnrS, ermF, ermT, ermX, sul1, sul2, sul3, tetA, tetB, and tetG) were selected as the targets. Adding FA to anaerobic digestion to remove antibiotics and resistance genes allows waste to be treated with waste. FA-based in situ AAD of sewage sludge effectively enhanced the process stability and methane yield, and the optimal FA-added dosage was 50 mg/L. The cumulative methane yield could be well described with the improved Gompertz model. FA addition effectively increased the overall removal of ofloxacin, by up to 85.3% at 50 mg/L FA and 10 μg/L antibiotics, and the combination of zero-valent iron and FA enhanced only the overall removal of ofloxacin to 92.4% and tetracycline to 85.6%. However, FA-based in situ AAD could not enhance the overall removal of other antibiotics from sewage sludge. Not all the same types of antibiotic resistance genes were strongly positively correlated with the concentrations of antibiotics. The removal of antibiotic resistance genes influenced by FA addition varied largely with the types of antibiotic resistance genes, FA dosage, antibiotic content, and the combination with zero-valent iron. FA addition could not be verified to enhance the removal of antibiotic resistance genes. The addition of FA or zero-valent iron and the antibiotic concentrations significantly changed the microbial community structure during in situ AAD, and the combination of zero-valent iron and FA significantly reduces the species diversity and microbial abundance. The most abundant bacteria were Methanogarcina, Methanoberium, unidentified_Archaea, Terrimonas, Methomethoxychlorovorans, and Candidatus_Cloacimonas in the ZVI-FA test.

Incomprehension concerning heavy metal containing finished solid leather wastes leads to environmental pollution. Conversion of these solid leather waste into energy and resource efficient products proves to be challenging. However, leather microfibres (LMF) were isolated from these heavy metal containing finished solid leather wastes. These heavy metal contain LMF further processed into metal reduction LMF. The metal reduction LMF were investigated for their heavy metal removal efficiency and toxicity analysis. The Cr (III) and Cr (VI) content of LMF was <1000 μg/mL and <800 μg/mL, respectively. Toxicity estimation was proved that the LMF had less than 1%. The study attempt to prepare reconstituted fibric materials (RFM) from metal reduction LMF and cellulose nanofibres (CNF). RFM were characterized for their physicochemical and mechanical properties. Hence, the study has proved a novel concept of RFM production which is recyclable, environmental friendly and cost effective.

Decentralized solid-waste incinerators (DSWIs) have certain advantages for waste disposal from villages and towns. However, the incineration condition is always affected by the distribution of temperature and oxygen concentration, which causes difficulties in operation and maintenance. In this study, the temperature and oxygen concentration distribution of DSWI were characterized using different air flow rates and bottom ash volumes. The results showed that the adjustment of air flow has no significant influence on the heating process of the DSWI, while the retention of bottom ash did affect the temperature and oxygen concentration fields in the furnace. When the air flow rate was increased without the retention of bottom ash, 99% of the furnace volume temperature was observed between 780 °C and 800 °C. However, once the bottom ash was retained, the whole furnace temperature was steadily maintained between 800 °C and 850 °C. When the air flow rate was increased without bottom ash, the highest furnace volume percentage of oxygen concentrations higher than 3% maxed out at 11% volume, while it could reach 100% when bottom ash remained. The distribution of the temperature and oxygen concentration in the DSWI characterized by this research provides strong support for the operation and management of such systems.

Appropriate solid waste management (SWM) strategies are necessary to avoid severe environmental and sanitary impacts, especially in low-income countries. Such strategies are most likely to succeed whether implementing actors are supported by scientific research. In this paper, the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane (Mozambique), integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city. The center is expected to receive about 0.3–0.4 t/day of plastic waste (5%–7% of the overall amount of plastic waste daily produced in Quelimane). As long-term sustainability represents a typical issue, simplicity of operation was a leading principle in the design of the center; moreover, the design included a treatment plant (WWTP) for generated wastewater, whose management is usually neglected in such interventions. Among others, natural wastewater treatment (constructed wetlands) has been chosen for its affordability. Noteworthy, the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants. The system is designed to treat an average flow of 6 m3/day and consisted of a septic tank followed by a subsurface flow constructed wetland. Overall, the COD (chemical oxygen demand) and TSS (total suspended solids) removal higher than 80% and 90% were estimated, respectively. Based on this work, both the center and the WWTP were successfully realized, which are waiting to become operational. In the authors’ opinion, the implemented procedure could become a reference for broader investigations and surveys.

In this study, coal slime was mainly utilized to conduct experiments on a 30 kW preheating combustion test rig to analyze the conversion pathway of sulfur during the experiment, aiming at reducing slime pollution, controlling sulfur emission reasonably, and providing theoretical support for the preheating combustion technology. The results showed that after the coal slime was preheated, a large number of elements were released. The maximum release rates for H and S were 94.0% and 73.3%, respectively. The released S was converted into the sulfur-containing gases like H2S, COS, CS2, and the rest existed in the solid in the five forms of mercaptan, thiophene, sulfoxide, sulfone, and sulfate. Besides, during the combustion process, the gas was oxidized continuously and finally converted into SO2, leaving only the sulfate in the fly ash. In the preheating combustion process, 26.7% of the S was released from the coal, 73.3% of the S was retained in the semi-coke, and the final SO2 emission concentration of combustion was 959 ppm.