Co-Combustion of Waste Tires and Plastic-Rubber Wastes with Biomass Technical and Environmental Analysis

Thermal and Catalytic Recycling of Plastics from Waste Electrical and Electronic Equipment-Challenges and Perspectives

The amount of end-of-life electrical and electronic devices has been widely increased, globally. This emphasizes how recycling waste electric and electronic equipment (WEEE) is essential in order to reduce the amount of WEEE that is disposed of directly in the environment. Plastics account for a big percentage in WEEE, almost 20%. As a result, the application of recycling methods on plastics gathered from WEEE is of great importance since, in this way, landfill disposal can be reduced. Nevertheless, despite the advantages, there are a lot of difficulties, such as the variety of different plastics present in the plastic mix and the existence of various additives in the plastic parts, for instance, brominated flame retardants that need special attention during their treatments, which restricts their wide application. Considering all these, this review aims to provide readers with all the current techniques and perspectives that are available for both the thermal and the catalytic recycling of plastics retrieved from WEEE. Apart from the up-to-date information on the recycling methods, in this review, emphasis is also given on the advantages each method offers and also on the difficulties and the limitations that may prevent them from being applied on a large scale. Current challenges are critically examined, including the use of mechanical or thermo-chemical recycling, the treatment of individual polymers or polymer blends and the separation of harmful additives before recycling or not. Finally, emerging technologies are briefly discussed.

WEEE polymers valorization, its use as fuel in the gasification process and revaluation of the inert by-products obtained: Sustainable mortars as a solution

The global production of polymer materials has exploded in the last few decades. Their mechanical properties, erosion and corrosion resistance, good performance as insulation materials, and their ease and flexibility of manufacturing have made polymers one of the most widely used materials in the industry and in daily life. Several institutions and governments are beginning to raise serious environmental and ecological concerns with international impact soon, due to the increasing level of polymer production, which does not seem to be slowing down. It is necessary for the scientific community to make efforts in the development and evaluation of new methodologies to enable the inclusion of these types of materials in the circular economy of various production sectors. This is important in order to reduce the ecological impact caused by the current global production level of polymers. One of the most used methods for the recovery of polymeric materials is energy valorization through thermochemical processes. An example of this is thermal gasification using fuels composed of biomass and a mixture of polymeric waste from electrical and electronic equipment (WEEE). Through this thermochemical process, high-energy value synthesis gas, with a high concentration of hydrogen, is obtained on one hand, while waste products in the form of chars, ashes and slag are generated on the other hand. This manuscript presents a detailed study methodology that begins with chemical analysis of the raw material and includes subsequent analysis of mechanical results for the revaluation of these residual inert by-products, using them as partial substitutes in cement clinker to produce building mortars. This described methodology influences directly in the LCC (Life Cycle Costing) of final designed products in plastic and extend material life cycle Plastic materials are here to stay, so the study and optimization of polymer waste recovery processes are vital in achieving the Sustainable Development Goals (SDGs) set by the European Union in terms of efficiency and sustainability. It is also the only possible way to create an environmentally sustainable future world for future generations. After applying the described methodology, the mechanical test results show that the modified mortars exhibit established behaviour during the hardening time and similar strength growth compared to commercial mortars. The maximum mechanical strengths achieved, including compressive and flexural strength, make modified mortars a viable choice for several applications in the civil engineering sector.

Energy Recovery from Polymeric 3D Printing Waste and Olive Pomace Mixtures via Thermal Gasification-Effect of Temperature

One of the polymeric materials used in the most common 3D printers is poly(ethylene terephthalate) glycol (PETG). It represents, in world terms, around 2.3% of polymeric raw material used in additive manufacturing. However, after processing this material, its properties change irreversibly. A significant amount of waste is produced around the world, and its disposal is usually destined for landfill or incineration, which can generate an important issue due to the high environmental risks. Polymer waste from 3D printing, hereinafter 3DPPW, has a relatively high calorific value and adequate characteristics to be valued in thermochemical processes. Gasification emerges as an innovative and alternative solution for recovering energy from 3DPPW, mixed with residues of lignocellulosic origin, and presents some environmental advantages compared to other types of thermochemical treatments, since the gasification process releases smaller amounts of NOx into the atmosphere, SOx, and CO₂. In the case of the study, co-gasification of olive pomace (OLB) was carried out with small additions of 3DPPW (10% and 20%) at different temperatures. Comparing the different gasifications (100% OLB, 90% OLB + 10% 3DPPW, 80% OLB + 20% 3DPPW), the best results for the synthesis gas were obtained for the mixture of 10% 3DPPW and 90% olive pomace (OLB), having a lower calorific value of 6.16 MJ/m³, synthesis gas yield of 3.19%, and cold gas efficiency of 87.85% for a gasification temperature of 750 °C. In addition, the results demonstrate that the addition of 3DPPW improved the quality of syngas, especially between temperatures of 750 and 850 °C. Including polymeric 3D printing materials in the context of the circular economy and extending their life cycle helps to improve the efficiency of subsequent industrial processes, reducing process costs in general, thanks to the new industrial value acquired by the generated by-products.

Fire Resistance Evaluation of New Wooden Composites Containing Waste Rubber from Automobiles

Particleboards containing waste rubber (tires and mixtures of isolators and carpets) filler were evaluated from the point of view of its flammability. The assessment of the utilization of these composites in the construction industry was analyzed through the determination of their spontaneous ignition temperatures, mass burning rate and calorific value. Based on the results of spontaneous ignition temperatures, similar values between particleboards and particleboards containing 10%, 15% and 20% of waste tires were obtained. The average time was from 298 s to 309 s and the average temperature was from 428.1 °C to 431.7 °C. For the mass burning rate, there were similar results between particleboards and particleboards containing 10% of waste tires and waste rubber. The time to initiation was 34 s and the time to reaching a maximal burning rate was from 66 s to 68 s. The calorimetry results showed similar properties for the calorimetric value and ash content in particleboards and particleboards containing 10% of waste tires and waste rubber. The calorific value was from 18.4 MJ·kg^-1 to 19.7 MJ·kg^-1 and the ash content from 0.5% to 2.9%.

Thermo-soil weathering and life cycle assessment of carbon black, silica and cellulose nanocrystal filled rubber nanocomposites

Carbon black (CB) and silica (Sil) as rubber reinforcement have raised environmental concerns for being high resources consumptive and less susceptible towards biodegradability. Cellulose nanocrystal (CNC) has demonstrated great potentials for use as biodegradable nanofillers in rubber nanocomposites while evaluation of its environmental impacts with optimal end-of-life (EOL) choices is not carried out. To simulate realistic EOL, thermo-oxidative aging and soil burial aging behaviors of rubber nanocomposites with 33.3% filler were performed. The environmental weathering performance modeled with the help of life cycle assessment (LCA) illustrates increased biodegradation susceptibility with partial replacement of CB or Sil with CNC in the nanocomposites, hence promoting the environmental solutions for waste minimalization by enhancing the biodegradability potentials. In terms of LCA, the CNC incorporation contributes more to the environmental impacts in manufacturing but greatly lowers the EOL choices, by reducing the global warming potential values.

Energy and Environmental Assessment of Steam Management Optimization in an Ethylene Plant

Steam crackers (ethylene plants) belong to the most complex industrial plants and offer significant potential for energy-saving translated into the reduction of greenhouse gas emissions. Steam export to or import from adjacent units or complexes can boost the associated financial benefit, but its energy and environmental impact are questionable. A study was carried out on a medium-capacity ethylene plant using field data to: 1. Estimate the energy savings potential achievable by optimizing internal steam management and optimizing steam export/import; 2. Quantify the associated change in air pollutant emissions; 3. Analyze the impact of the increasing carbon price on the measures adopted. Internal steam management optimization yielded steam let-down rate minimization and resulted in a 5% (87 TJ/year) reduction in steam cracker’s steam boiler fuel consumption and the associated cut of CO₂ emissions by almost 4900 t/year and that of NO_x emissions by more than 5 t/year. Steam import to the ethylene plant from the refinery proved to be purely economic-driven, as it increased the net fuel consumption of the ethylene plant and the refinery complex by 12 TJ/year and resulted in an increase of net emissions of nearly all considered air pollutants (more than 7000 t/year of CO₂, over 15 t/year of NO_x, over 18 t/year of SO_x) except for CO, where the net change was almost zero. The effect of external emissions change due to the associated backpressure electricity production surplus (over 11 GWh/year) was too low to compensate for this increase unless fossil fuel-based electricity production was considered. The increase of carbon price impact on the internal steam management optimization economics was favorable, while a switch to steam export from the ethylene plant, instead of steam import, might be feasible if the carbon price increased to over 100 €/tCO₂.

Odour Nuisance at Municipal Waste Biogas Plants and the Effect of Feedstock Modification on the Circular Economy—A Review

The increase in the amount of municipal solid waste (MSW) generated, among other places, in households is a result of the growing population, economic development, as well as the urbanisation of areas with accompanying insufficiently effective measures to minimise waste generation. There are many methods for treating municipal waste, with the common goal of minimising environmental degradation and maximising resource recovery. Biodegradable waste, including selectively collected biowaste (BW), also plays an essential role in the concept of the circular economy (CE), which maximises the proportion of waste that can be returned to the system through organic recycling and energy recovery. Methane fermentation is a waste treatment process that is an excellent fit for the CE, both technically, economically, and environmentally. This study aims to analyse and evaluate the problem of odour nuisance in municipal waste biogas plants (MWBPs) and the impact of the feedstock (organic fraction of MSW-OFMSW and BW) on this nuisance in the context of CE assumptions. A literature review on the subject was carried out, including the results of our own studies, showing the odour nuisance and emissions from MWBPs processing both mixed MSW and selectively collected BW. The odour nuisance of MWBPs varies greatly. Odour problems should be considered regarding particular stages of the technological line. They are especially seen at the stages of waste storage, fermentation preparation, and digestate dewatering. At examined Polish MWBPs cod ranged from 4 to 78 ou/m3 for fermentation preparation and from 8 to 448 ou/m3 for digestate dewatering. The conclusions drawn from the literature review indicate both the difficulties and benefits that can be expected with the change in the operation of MWBPs because of the implementation of CE principles.

Developments in waste tyre thermochemical conversion processes: gasification, pyrolysis and liquefaction

Fossil fuels, particularly crude oil, have proven to be a source of energy to households, transportation and power industries over the past decades. This natural reserve is diminishing at an alarming rate with crude oil having reserves to last the earth for the next half a century. As a result, researchers are constantly seeking remedial technologies to close this gap. Thermochemical conversion processes such as pyrolysis, gasification and liquefaction (PGL) offer an alternative solution to mitigating the world's high reliance on crude oil. These processes can be employed to provide energy, fuel and high-end value-added products. This paper aims to highlight all the research and development advancements and trends that have been made over the past three decades while employing waste tyres and other feedstock. In addition, the prominent countries and their associated researchers who have made novel discoveries in the field of thermochemical conversion are extensively discussed. The research findings show that significant research outputs such as the utilization of vast types of feed materials, the reaction mechanisms, the factors affecting the processes, and the application of the different end-products for thermochemical processes are well documented in the literature. Also, the collected data showed that significant advancements have been achieved in developing PGL technologies. The following conclusions were drawn: (i) PGL technologies show a generally increasing percentage interest from 1990 to 2020, (ii) many authors have identified the end-products obtained from waste feedstocks, such as; waste tyres, biomass, plastics, food waste, microalgae and animal manure to yield promising application benefits, (iii) China has shown the greatest interest in investing into waste to energy initiatives and has demonstrated the vast applications of waste derived products and, (iv) employing waste tyres as a feedstock has shown potential for producing high-end value products in their crude form or refined form. Some of the shortcomings identified during the study are the modest interest shown by most African regions as well as the lack of regulatory frameworks developed by certain countries.

Fossil fuels, particularly crude oil, have proven to be a source of energy to households, transportation and power industries over the past decades.

Advances in Biomass Co-Combustion with Fossil Fuels in the European Context: A Review

Co-combustion of biomass-based fuels and fossil fuels in power plant boilers, utility boilers, and process furnaces is a widely acknowledged means of efficient heat and power production, offering higher power production than comparable systems with sole biomass combustion. This, in combination with CO2 and other greenhouse gases abatement and low specific cost of system retrofit to co-combustion, counts among the tangible advantages of co-combustion application. Technical and operational issues regarding the accelerated fouling, slagging, and corrosion risk, as well as optimal combustion air distribution impact on produced greenhouse gases emissions and ash properties, belong to intensely researched topics nowadays in parallel with the combustion aggregates design optimization, the advanced feed pretreatment techniques, and the co-combustion life cycle assessment. This review addresses the said topics in a systematic manner, starting with feed availability, its pretreatment, fuel properties and combustor types, followed by operational issues, greenhouse gases, and other harmful emissions trends, as well as ash properties and utilization. The body of relevant literature sources is table-wise classified according to numerous criteria pertaining to individual paper sections, providing a concise and complex insight into the research methods, analyzed systems, and obtained results. Recent advances achieved in individual studies and the discovered synergies between co-combusted fuels types and their shares in blended fuel are summed up and discussed. Actual research challenges and prospects are briefly touched on as well.

Energy Recovery via Thermal Gasification from Waste Insulation Electrical Cables (WIEC)

The recovery of noble metals from electrical wires and cables results in waste materials such as polyvinyl chloride (PVC) and polyethylene (PE), that is, waste insulation electrical cables (WIEC), which have been processed by gasification for energy recovery. This study focused on the effect of blending the ratio of WIEC on the gasification feedstock composition and the lower heating value (LHV) of produced syngas, through controlled tests and tests under different loads on the generator. The controlled gasification experiments were carried out at blending ratios between pine biomass and WIEC of 90:10, 80:20, and 70:30 and with pine biomass only (100%). For the loads gasification, the experiments were carried out at a blending ratio of 80:20. The controlled experimental results presented that the highest hydrogen content, approximated 17.7 vol.%, was observed at a blending ratio of 70:30 between pine biomass and WIEC and the highest LHV of syngas was observed at a blending ratio of 90:10, with 5.7 MJ/Nm3. For the load gasification experiments, the results showed that the highest hydrogen content was obtained with a load of 15 kW in the generator, approximately 18.48 vol.% of hydrogen content, and the highest LHV of synthesis gas was observed during the 5 kW test, with 5.22 MJ/Nm3. Overall, the new processing of waste insulation electrical cables using a downdraft gasification reactor demonstrates great promise for high quality syngas production.

Anaerobic Digestion Performance: Separate Collected vs. Mechanical Segregated Organic Fractions of Municipal Solid Waste as Feedstock

The replacement of fossil fuel with renewable energy sources seems as though it will be crucial in the future. On the other hand, waste generation increases year by year. Thus, waste-to-energy technologies fit in with the actual trends, such as the circular economy. The crucial type of generated waste is municipal solid waste, which is in the research area. Regarding the organic fraction of municipal solid waste (OFMSW), anaerobic digestion (AD) allows the recovery of biogas and energy. Furthermore, if it is supported by source segregation, it should allow the recovery of material as fertilizer. The AD process performance (biogas yield and stability) comparison of source-segregated OFMSW (ss-OFMWS) and mechanically sorted OFMSW (ms-OFMSW) as feedstocks was performed in full-scale conditions. The daily biogas volume and methane content were measured to assess AD efficiency. To verify the process stability, the volatile fatty acid (VFA) content, pH value, acidity, alkalinity, and dry matter were determined. The obtained biogas yield per ton was slightly higher in the case of ss-OFMSW (111.1 m3/ton), compared to ms-OFMSW (105.3 m3/ton), together with a higher methane concentration: 58–60% and 51–53%, respectively, and followed by a higher electricity production capacity of almost 700 MWh for ss-OFMSW digestion. The obtained VFA concentrations, at levels around 1.1 g/kg, pH values (slightly above 8.0), acidity, and alkalinity indicate the possibilities of the digester feeding and no-risk exploitation of either as feedstock.

Thermochemical and Economic Analysis for Energy Recovery by the Gasification of WEEE Plastic Waste from the Disassembly of Large-Scale Outdoor Obsolete Luminaires by LEDs in the Alto Alentejo Region (Portugal)

The recovery of urban waste is a social demand and a measure of the energy-environmental sustainability of cities and regions. In particular, waste of electrical origin, waste of electrical and electronic materials (WEEE) can be recovered with great success. The plastic fraction of these wastes allows their gasification mixed with biomass, and the results allow for producing syngas with a higher energy potential. This work allows for obtaining energy from the recovery of obsolete materials through thermochemical conversion processes of the plastic waste from the disassembly of the luminaires by mixing the said plastic waste in different proportions with the biomass of crop residues (olive). The gasification tests of these mixtures were carried out in a downstream fixed-bed drown daft reactor, at temperatures of approximately 800 °C. The results demonstrate the applied technical and economic feasibility of the technology by thermal gasification, for the production of LHV (Low Heating Value) syngas with highest power energy (more than 5 MJ/m3) produced in mixtures of up to 20% of plastic waste. This study was complemented with the economic-financial analysis. This research can be used as a case study for the energy recovery through gasification processes of plastic waste from luminaires (WEEE), mixed with agricultural biomass that is planned to be carried out on a large scale in the Alentejo (Portugal), as a solution applied in circular economy strategies.

Analysis of CO2 Drivers and Emissions Forecast in a Typical Industry-Oriented County: Changxing County, China

Decomposing main drivers of CO2 emissions and predicting the trend of it are the key to promoting low-carbon development for coping with climate change based on controlling GHG emissions. Here, we decomposed six drivers of CO2 emissions in Changxing County using the Logarithmic Mean Divisia Index (LMDI) method. We then constructed a model for CO2 emissions prediction based on a revised version of the Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model and used it to simulate energy-related CO2 emissions in five scenarios. Results show that: (1) From 2010 to 2017, the economic output effect was a significant, direct, dominant, and long-term driver of increasing CO2 emissions; (2) The STIRPAT model predicted that energy structure will be the decisive factor restricting total CO2 emissions from 2018 to 2035; (3) Low-carbon development in the electric power sector is the best strategy for Changxing to achieve low-carbon development. Under the tested scenarios, Changxing will likely reach peak total CO2 emissions (17.95 million tons) by 2030. Measures focused on optimizing the overall industrial structure, adjusting the internal industry sector, and optimizing the energy structure can help industry-oriented counties achieve targeted carbon reduction and control, while simultaneously achieving rapid economic development.