Curbing dioxin emissions from municipal solid waste incineration: China's action and global share

Solidification and utilization of municipal solid waste incineration ashes: Advancements in alkali-activated materials and stabilization techniques, a review

Researchers are actively investigating methodologies for the detoxification and utilization of Municipal Solid Waste Incineration Bottom Ash (MSWIBA) and Fly Ash (MSWIFA), given their potential as alkali-activated materials (AAMs) with low energy consumption. Recent studies highlight that AAMs from MSWIFA and MSWIBA demonstrate significant durability in both acidic and alkaline environments. This article provides a comprehensive overview of the processes for producing MSWIFA and MSWIBA, evaluating innovative engineering stabilization techniques such as graphene nano-platelets and lightweight artificial cold-bonded aggregates, along with their respective advantages and limitations. Additionally, this review meticulously incorporates relevant reactions. Recommendations are also presented to guide future research endeavors aimed at refining these methodologies.

Comparing and optimizing municipal solid waste (MSW) management focused on air pollution reduction from MSW incineration in China

China is the largest developing country in the world, and its municipal solid waste (MSW) has increased with a compound annual growth rate of 5.1 % since 1980. Incineration, which has the advantages of mass- and volume-reduction as well as energy and heat recovery, has become the mainstream environmentally sound treatment method in China. However, air pollution emissions are the primary reason for limiting MSW incineration (MSWI). Currently, the Chinese government is devoted to comprehensively implementing MSW classification. However, the classification model and the future MSW reduction rate are not yet clear. In this study, we project scenarios of air pollution emissions until 2030 based on the different MSW classification models (MSW reduction rates) and diffusion rates of ultra-low emission technology. A total of 6011 tons (t) of particulate matter, 25,881 t of SO2, 14,915 t of CO, 17,167 t of HCl, and 200,166 t of NOx will be emitted in 2030 under the business-as-usual (BAU) scenario, and air pollutants will not peak under this scenario. Air pollutants will reduce by 11 % of the BAU scenario by only implementing an MSW reduction of 20 % (JPN-model). The optimal scenario (DEU-model, increasing the efficiency of material recovery and upgrading air pollution control devices) means that air pollutants will be reduced by 83.2-96.2 % from the base amount under the BAU scenario. These results provide references for MSW management and air pollution emission reduction from the aspects of MSW classification and technology upgrades in China.

First principles insights into the interaction mechanism of iron doped thermally activated kaolinite with Cd and Pb pollutants in organic solid waste incineration flue gas

Incineration of organic solid wastes is accompanied by the heavy metal emission through flue gas. As an inexpensive and efficient heavy metal adsorbent, the improvement of kaolinite adsorption performance for heavy metals has drawn widespread interests. In this work, the interaction mechanisms between various kaolinite surfaces and Cd/Pb species are explored through first principles calculations. The results show that the combination of Fe doping and dehydroxylation enhances the activity of kaolinite surfaces, analysis of adsorption configurations reveal that both Cd and Pb species are immobilized through chemisorption on the -H + Fe surface. At the microscopic level, further electronic structure analysis shows that the composite modified kaolinite surface has more electron transfer and more pronounced orbital hybridization and overlap compared to the original kaolinite surface, demonstrating that the modification means of dehydroxylation and Fe doping indeed enhanced the activity of the kaolinite surface, especially the activity of the O atoms in the vicinity of the Fe atom and that the O atoms are more efficiently bonded as ionic connecting Cd/Pb species for the purpose of trapping Cd/Pb species. This study points out the research direction and provides basic theoretical support for the development of new kaolinite adsorbents in the future.

Environmental impact assessment of multi-source solid waste based on a life cycle assessment, principal component analysis, and random forest algorithm

As a national pilot city for solid waste disposal and resource reuse, Dongguan in Guangdong Province aims to vigorously promote the high-value utilization of solid waste and contribute to the sustainable development of the Greater Bay Area. In this study, life cycle assessment (LCA) coupled with principal component analysis (PCA) and the random forest (RF) algorithm was applied to assess the environmental impact of multi-source solid waste disposal technologies to guide the environmental protection direction. In order to improve the technical efficiency and reduce pollution emissions, some advanced technologies including carbothermal reduction‒oxygen-enriched side blowing, directional depolymerization‒flocculation demulsification, anaerobic digestion and incineration power generation, were applied for treating inorganic waste, organic waste, kitchen waste and household waste in the park. Based on the improved techniques, we proposed a cyclic model for multi-source solid waste disposal. Results of the combined LCA-PCA-RF calculation indicated that the key environmental load type was human toxicity potential (HTP), came from the technical units of carbothermal reduction and oxygen-enriched side blowing. Compared to the improved one, the cyclic model was proved to reduce material and energy inputs by 66%-85% and the pollution emissions by 15%-88%. To sum up, the environmental impact assessment and systematic comparison suggest a cyclic mode for multi-source solid waste treatments in the park, which could be promoted and contributed to the green and low-carbon development of the city.

Municipal solid waste treatment for bioenergy and resource production: Potential technologies, techno-economic-environmental aspects and implications of membrane-based recovery

World estimated municipal solid waste generating at an alarming rate and its disposal is a severe concern of today's world. It is equivalent to 0.79 kg/d per person footprint and causing climate change; health hazards and other environmental issues which need attention on an urgent basis. Waste to energy (WTE) considers as an alternative renewable energy potential to recover energy from waste and reduce the global waste problems. WTE reduced the burden on fossil fuels for energy generation, waste volumes, environmental, and greenhouse gases emissions. This critical review aims to evaluate the source of solid waste generation and the possible routes of waste management such as biological landfill and thermal treatment (Incineration, pyrolysis, and gasification). Moreover, a comparative evaluation of different technologies was reviewed in terms of economic and environmental aspects along with their limitations and advantages. Critical literature revealed that gasification seemed to be the efficient route and environmentally sustainable. In addition, a framework for the gasification process, gasifier types, and selection of gasifiers for MSW was presented. The country-wise solutions recommendation was proposed for solid waste management with the least impact on the environment. Furthermore, key issues and potential perspectives that require urgent attention to facilitate global penetration are highlighted. Finally, practical implications of membrane and comparison membrane-based separation technology with other conventional technologies to recover bioenergy and resources were discussed. It is expected that this study will lead towards practical solution for future advancement in terms of economic and environmental concerns, and also provide economic feasibility and practical implications for global penetration.

Effect of Hybrid Filler, Carbon Black-Lignocellulose, on Fire Hazard Reduction, including PAHs and PCDDs/Fs of Natural Rubber Composites

The smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of lignocellulose filler, we noticeably reduced the fire hazard caused by elastomeric composites. The lignocellulose filler reduced the parameters associated with the flammability of the tested composites, decreased the smoke emission, and limited the toxicity of gaseous decomposition products expressed as a toximetric indicator and the sum of PAHs and PCDDs/Fs. The natural filler also reduced emission of gases that constitute the basis for determination of the value of the toximetric indicator W_LC50SM. The flammability and optical density of the smoke were determined in accordance with the applicable European standards, with the use of a cone calorimeter and a chamber for smoke optical density tests. PCDD/F and PAH were determined using the GCMS-MS technique. The toximetric indicator was determined using the FB-FTIR method (fluidised bed reactor and the infrared spectrum analysis).

Converting food waste into soil amendments for improving soil sustainability and crop productivity: A review

One-third of the annual food produced globally is wasted and much of the food waste (FW) is unutilized; however, FW can be valorized into value-added industrial products such as biofuel, chemicals, and biomaterials. Converting FW into soil amendments such as compost, vermicompost, anaerobic digestate, biofertilizer, biochar, and engineered biochar is one of the best nutrient recovery and FW reuse approaches. The soil application of FW-based amendments can improve soil fertility, increase crop production, and reduce contaminants by altering soil's chemical, physical, microbial, and faunal properties. However, the efficiency of the amendment for improving ecosystem sustainability depends on the type of FW, conversion method, application rate, soil type, and crop type. Engineered biochar/biochar composite materials produced using FW have been identified as promising amendments for soil remediation, reducing commercial fertilizer usage, and increasing soil nutrient use efficiency. The development of quality standards and implementation of policies and regulations at all stages of the food supply chain are necessary to manage (reduce and re-use) FW.

Polybrominated dibenzo-p-dioxins/furans and their chlorinated analogues in sediments from a historical hotspot for both brominated flame retardants and organochlorine pesticides

Polybrominated dibenzo-p-dioxin/furans (PBDD/Fs) and polychlorinated dibenzo-p-dioxin/furans (PCDD/Fs) in the environment are closely related to their precursors, brominated flame retardants (BFRs) and organochlorine pesticides (OCPs). However, their change trends following the regulation of BFRs and OCPs remain incompletely characterized. Here, we examined PBDD/Fs and PCDD/Fs in sediments from a historical hotspot for both BFRs and OCPs, namely the Pearl River Delta (PRD), China. PBDD/Fs showed ubiquity in these samples but significantly lower concentrations than PCDD/Fs. Spatially, the occurrence of PBDD/Fs was positively correlated with local development levels and sediments from highly urbanized/industrialized areas showed higher and increasing PBDD/F concentrations. Polybrominated diphenyl ether (PBDE)-related products/industries were the greatest PBDD/F contributors to the PRD, followed by bromo-phenol/benzene-related products/industries. PCDD/Fs in PRD sediments showed significant positive correlations with local grain planting area, yield, and pesticide consumption. The historical use of pentachlorophenol (PCP)/PCP-Na and biomass open-burning were the leading PCDD/F sources of the PRD agricultural/rural areas, where the concentrations and toxic equivalent quantities (TEQs) of PCDD/Fs in sediments changed very little over the past decade. Anthropogenic thermal processes involved in metallurgy, waste incineration, and vehicles were the greatest PCDD/F contributors in the PRD urban/industrial areas, where the PCDD/F concentrations in sediments almost doubled over the last decade. This finding indicates the increasing PCDD/F contributions of industrial and municipal activities in the PRD, despite the implementation of strict emission standards. Over sixty percent of the samples showed TEQs that surpassed the low-risk threshold specified for mammalian life by the U.S. EPA (2.5 pg TEQ g^-1) and warrant continuous attention.

MSWNet: A visual deep machine learning method adopting transfer learning based upon ResNet 50 for municipal solid waste sorting

An intelligent and efficient methodology is needed owning to the continuous increase of global municipal solid waste (MSW). This is because the common methods of manual and semi-mechanical screenings not only consume large amount of manpower and material resources but also accelerate virus community transmission. As the categories of MSW are diverse considering their compositions, chemical reactions, and processing procedures, etc., resulting in low efficiencies in MSW sorting using the traditional methods. Deep machine learning can help MSW sorting becoming into a smarter and more efficient mode. This study for the first time applied MSWNet in MSW sorting, a ResNet-50 with transfer learning. The method of cyclical learning rate was taken to avoid blind finding, and tests were repeated until accidentally encountering a good value. Measures of visualization were also considered to make the MSWNet model more transparent and accountable. Results showed transfer learning enhanced the efficiency of training time (from 741 s to 598.5 s), and improved the accuracy of recognition performance (from 88.50% to 93.50%); MSWNet showed a better performance in MSW classsification in terms of sensitivity (93.50%), precision (93.40%), F1-score (93.40%), accuracy (93.50%) and AUC (92.00%). The findings of this study can be taken as a reference for building the model MSW classification by deep learning, quantifying a suitable learning rate, and changing the data from high dimensions to two dimensions.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s11783-023-1677-1 and is accessible for authorized users.

Research on Pavement Performance of Cement-Stabilized Municipal Solid Waste Incineration Bottom Ash Base

In order to clarify the influence of the municipal solid waste incineration bottom ash (MSWI BA) content on the pavement performance of the cement-stabilized macadam, the MSWI BA with 0%, 25%, 38% and 50% content was used instead of fine aggregates. To explore the feasibility of building pavement base with cement stabilized MSWI BA, the cement-stabilized MSWI BA mixture was prepared by mixing the MSWI BA at the mass fraction of 50%, 75% and 100% with fine crushed stuff. Subsequently, the compaction test and 7 days unconfined compression test were conducted with 4%, 5% and 6% cement dosage. The compaction test, unconfined compressive strength test, splitting strength test, compressive resilient modulus test and frost resistance tests were carried out based on the long-age samples with an optimal cement dosage of 5%. Furthermore, the unconfined compressive constitutive model was established based on the test data. Afterwards, the test road was built to measure the practical effect of MSWI BA on road construction. Meanwhile, energy-saving and emission-reduction analyses were conducted on the MSWI BA road. The results showed that under 5% cement dosage, the mechanical properties and frost resistance of the mixture with different MSWI BA content both satisfied the specification requirements; during the construction, the appropriate MSWI BA content could be selected according to the requirements of different highway grades in the specification. The established segmented constitutive model could well simulate the stress-strain relationship of the mixture in the compressive process. Using cement-stabilized MSWI BA to build the pavement base was feasible, which provided not only an important reference for the engineering design but also had positive significance for promoting carbon peaking, carbon neutrality and sustainable development of highway engineering construction.

A FRET Fluorescent Sensor for Ratiometric and Visual Detection of Sulfide Based on Carbon Dots and Silver Nanoclusters

In this work, the fluorescent sensor based on fluorescence resonance energy transfer (FRET) and electrostatic interaction (EI) was prepared for the ratiometric and visual detecting S^2-. The FRET fluorescent sensor consists of two fluorophores, with carbon dots (CDs) as energy donors and silver nanoclusters (Ag NCs) as acceptors. At 390 nm excitation, CDs and Ag NCs showed two well-separated peaks at 445 nm and 660 nm, separately. The existence of S^2- caused the red fluorescence at 660 nm to be quenched, whereas the blue fluorescence at 445 nm was restored, and the fluorescence color of the ratiometric sensor changed from pink to blue. It could be employed in ratiometric and visual detecting S^2-. The linear range of quantitative detection S^2- was 0.5-100 μM, and its detection limit was 0.35 μM. CDs-Ag NCs could be used for detecting S^2- in mineral water and tap water. The results showed that the FRET ratiometric fluorescent sensor exhibits good anti-interference and high selectivity for detecting S^2- in environmental water samples.