From waste plastics to industrial raw materials: A life cycle assessment of mechanical plastic recycling practice based on a real-world case study.

As the world’s largest producer and consumer of plastics, China is also the largest producer and recycler of waste plastics. It is necessary to explore the environmental impacts of actual end-of-life (EOL) treatments of waste plastics in China. In this study, a life cycle assessment (LCA) was conducted to evaluate the environmental impacts of mechanical recycling of waste plastics as well as incineration and landfilling with municipal solid waste in China. The results indicate the environmental benefits of current EOL treatments of waste plastics in China. Mechanical recycling was a negative and decisive contributor, with a minimum impact on terrestrial acidification potential (-83.4%) and a maximum impact on global warming potential (-165.8%). Incineration had negative contributions to 8 of the 12 environmental indicators, and landfilling was a positive contributor to all environmental impacts. Scenarios of treatment pattern, recycling technologies and import policy were set to analyze the potential reduction in environmental impacts of future EOL treatments of waste plastics. Increasing the proportion of mechanical recycling would reduce all environmental impacts, including up to 51.8% on particulate matter formation potential. Energy conservation and emission reduction in atmospheric pollutants would effectively reduce the environmental impacts of mechanical recycling. Banning waste plastics imports would decrease the transportation distances of waste plastics, thereby reducing the related environmental impacts, most notably a reduction of 84.8% for marine ecotoxicity potential. This study provides robust references for waste plastics management in China.

Life cycle assessment of end-of-life treatments of waste plastics in China

Carbon-dependent alleviation of ammonia toxicity for algae cultivation and associated mechanisms exploration.

Many practical design and operating decisions on wastewater treatment plants can have significant impacts on the overall environmental performance, in particular the greenhouse gas (GHG) emissions. The main factor in this regard is the use of aerobic or anaerobic treatment technology. This paper compares the GHG production of a number of case studies with aerobic or anaerobic main and sludge treatment of domestic wastewater and also looks at the energy balances and economics. This comparison demonstrates that major advantages can be gained by using primarily anaerobic processes as it is possible to largely eliminate any net energy input to the process, and therefore the production of GHG from fossil fuels. This is achieved by converting the energy of the incoming wastewater pollutants to methane which is then used to generate electricity. This is sufficient to power the aerobic processes as well as the mixing etc. of the anaerobic stages. In terms of GHG production, the total output (in CO2 equivalents) can be reduced from 2.4 kg CO2/kg COD(removed) for fully aerobic treatment to 1.0 kg CO2/kg COD(removed) for primarily anaerobic processes. All of the CO2 produced in the anaerobic processes comes from the wastewater pollutants and is therefore greenhouse gas neutral, whereas up to 1.4 kg CO2/kg COD(removed) originates from power generation for the fully aerobic process. This means that considerably more CO2 is produced in power generation than in the actual treatment process, and all of this is typically from fossil fuels, whereas the energy from the wastewater pollutants comes primarily from renewable energy sources, namely agricultural products. Even a change from anaerobic to aerobic sludge treatment processes (for the same aerobic main process) has a massive impact on the CO2 production from fossil fuels. An additional 0.8 kg CO2/kg COD(removed) is produced by changing to aerobic sludge digestion, which equates for a typical 100,000 EP plant to an additional production of over 10 t CO2 per day. Preliminary cost estimates confirm that the largely anaerobic process option is a fully competitive alternative to the mainly aerobic processes used, while achieving the same effluent quality.

Greenhouse gas production in wastewater treatment - Process selection is the major factor

Plastic mulch: Tradeoffs between productivity and greenhouse gas emissions


 This study aimed to evaluate industrial wastes-based solid fuel (IWSF) carbon footprint from the boundary of the cradle-to-grave life cycle. It includes emissions released from the transportation, manufacturing of IWSF, waste disposal, utilization of IWSF in the cement manufacturing plant, and end of life of IWSF. The quantification of total IWSF carbon footprint measures greenhouse gas emissions, carbon dioxide, nitrous oxide, and methane and is expressed as carbon dioxide equivalent (CO2-eq). The CO2-eq emission factors are calculated based on Intergovernmental Panel on Climate Change (IPCC) guideline, and the information used in this study is obtained from the actual operation. The study confirmed that the total carbon footprint of IWSF is approximately 0.17 kg CO2-Eq. MJ-1 energy generated. The results show that the utilization of IWSF at a cement manufacturing plant is the key contributor to carbon footprint, contributing to 94.3% of the total percentage, with a quantitative value of 27,000.7 MT CO2-eq per year IWSF manufacturing stage with 2.6 %. Subsequently, CO2-eq emission reduction initiatives have been implemented by the IWSF manufacturer, able to reduce approximately 333 MT of CO2-eq emission and total cost saving of USD50 000 annually. This study proves that industrial hazardous waste can be a source of fuel with positive economic and environmental returns. Besides, it was noted from the study that while direct combustion of solid-derived fuels can efficiently produce heat, it can also lead to the generation of greenhouse gases during the production and use phases. In summary, to estimate GHG emissions from IWSF production, a Life Cycle Assessment- Carbon Footprint (LCA-CF) should be considered.

/pdf/carbon-footprint-evaluation-of-hazardous-waste-based-solid-2c6ry8lkx3.pdf

Carbon Footprint Evaluation of Hazardous Waste Based Solid Fuel: Application in a Cement Kiln

While industries are familiar with environmental management systems for continuous improvement of production processes and products, there are various green-concept-oriented methods that can address environmental concerns significantly. This work focused on adaptation of cleaner production strategy for enhancing environmental management systems. Specifically, this work developed self-implementable methodology that systematically leads to identification of cleaner production options to improve environmental performance and efficiency of manufacturing industry. The developed methodology aims at preventing or reducing carbon emission from production processes and activities. The proposed methodology comprises three steps. In step 1, the sources of carbon emission from the manufacturing industry are identified through materials and energy consumption and waste generation. In step 2, the fate of the sources of carbon emission is determined. The sources are to be prevented or reduced. In step 3, cleaner production options are generated. Cleaner production options include modification of key operating parameters in manufacturing processes, such as temperature, pressure and time; implementation of housekeeping practices; modification of production process; substitution of greener materials; adaptation of new technologies; training to workers and 3R (reuse, recover, recycle). The options are generated with investigative questions. A food manufacturing industry was selected as a case study to demonstrate the practicality of using the developed methodology to generate cleaner production options. A total of 15 specific cleaner production options were identified for the studied premise using the methodology proposed demonstrating the practicality of the developed methodology.

/pdf/a-methodology-for-identifying-cleaner-production-options-to-37nvn3tj37.pdf

A methodology for identifying cleaner production options to reduce carbon emission in the manufacturing industry

Cellulose Nanocrystals (CNCs) have significant properties such as low density, high specific resistance, excellent mechanical properties, biodegradability, low-cost, low abrasive nature, and reactive surface for easy modification. Water contamination from various sources has become a serious problem in recent years. Hence, this study will serve the good application of composite nanocellulose in treating the wax from batik wastewater which needs proper treatment before releasing into the environment. This study also was aimed to synthesize CNCs/PVA composite from coconut fibre and used as adsorbent for the removal of wax from batik industry. The adsorption process was optimized based on parameters such as CNCs dosage and contact time. CNCs/PVA composites were prepared by constant mixing of CNCs suspension in PVA solution at 50°C for 1 hour, dried at 60°C overnight and heat treated at 190°C for 1 hour. Design of Experiments (DOE) was used to study the effects of CNCs dosage to PVA polymer (1-6 %v/w), contact time (15 min to 180 min) at a constant temperature and agitation rate of 48°C and 180 rpm respectively. The highest percentage of wax removal recorded was 50.23% at the optimal conditions of 6 %v/w of CNCs dosage at 180 min. By using natural wastes, the cost of pre-treatment process can be reduced, and this method is much simpler than other conventional methods. Besides, the conversion of the waste to a useful adsorbent also indirectly helps in minimizing the solid wastes.

Heat-treated CNC/PVA composite from natural fibre for wax removal of batik wastewater treatment

Carbon dioxide emission reduction through cleaner production strategies in a recycled plastic resins producing plant

Carbon Footprint Evaluation of Industrial Wastes Based Solid Fuel in the Context of Its Use in a Cement Plant

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