The promise of plastics from plants Hillmyer, Marc A.
Science (American Association for the Advancement of Science),
11/2017, Letnik:
358, Številka:
6365
Journal Article
Recenzirano
Plant-derived feedstocks are increasingly competitive in plastics production
Polymers protect us from the elements, increase the fuel efficiency of cars, protect food from pathogens, help cure ...disease, and enable renewable-energy technologies. To promote, foster, and enable a sustainable society, we need polymers. Yet polymers can also create serious environmental challenges. Nearly all plastic packaging produced—more than 80 billion kg annually—originates from fossil resources and is disposed of after a relatively short period of use ( 1 , 2 ). An increasing fraction of plastic is recycled or incinerated to recover energy, but most ends up in landfills, littering cities or landscapes, and in the oceans ( 3 ). New recycling concepts ( 4 ), clean incineration, and the development of polymers that can rapidly degrade ( 5 ) will be key to addressing these problems. Shifting from petrochemical feedstocks to renewable resources—making plastics from plants—can also rectify some environmental challenges associated with petrochemical extraction and render plastics production sustainable (see the figure).
Sewage sludge from municipal wastewater treatment plants in Germany is currently disposed of via thermal treatment and agricultural utilization or used for landscaping. Increasing focus on hygiene, ...soil protection and most recently on phosphorus recovery combined with the associated legal changes leads to an increased relevance of thermal sewage sludge treatment processes. This article reviews existing technologies for thermal treatment of sewage sludge with a view to the situation in Germany. Thermal sewage sludge treatment can be divided into different processes: drying reduces high water contents of mechanically dewatered sewage sludge and often precedes subsequent treatment processes. Today, most of the sewage sludge in Germany is incinerated, about half in mono-incineration, mostly in stationary fluidized beds, and the other half in co-incineration, in particular in coal-fired power plants, cement kilns or, to a lesser extent, waste incineration plants. Some alternative thermal processes, mainly pyrolysis and gasification, but also metallurgical approaches, are tested in bench or pilot scale. Recent amendments to the German Sewage Sludge Ordinance will restrict the disposal route of co-incineration in future. Consequently, a significant increase in mono-incineration capacity is expected. These processes should enable the combination of environmentally friendly disposal and phosphorus recovery.
•Previous treatment paths for sewage sludge are compared with the current status.•Recently amended legal framework for sewage sludge treatment is summarized.•Current and past most common processes for mono-incineration are reviewed.•Disadvantages of co-incineration and alternative technologies are presented.•Future development of sewage sludge treatment is assessed on basis of this research.
The waste-to-energy (WTE) project can handle the expanding volume of municipal solid waste (MSW) and promote the development of the circular economy, effectively. To achieve sustainable MSW ...management, it is pivotal to select a promising WTE incineration plant site. Thus, this paper aims to propose a novel methodology for selecting the optimal WTE incineration plant site. A sustainable evaluation index system is constructed from the environment, economy, society, risk, and energy aspects. Evaluation criteria are articulated by mathematical models and hesitant fuzzy linguistic term set, respectively. Given interactional relations among criteria and computation efficiency, HFL-BWM-ANP (hesitant fuzzy linguistic Best-Worst method-Analytic Network Process) is proposed to obtain criteria weights. The double parameters TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) approach is employed to rank alternative sites. The feasibility of the proposed methodology is illustrated by a numerical case. Triple sensitivity analysis and comparative analysis are performed to demonstrate the robustness, effectiveness, and superiority of the proposed methodology. Some managerial insights are provided from multiple dimensions for investors and the government to implement the WTE incineration plant project.
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•Constructing a sustainable evaluation index system from multiple dimensions.•Articulating evaluation criteria by mathematical models and hesitant fuzzy linguistic term set, respectively.•Proposing a weighting model to improve efficiency and handle correlations among criteria.•Introducing the double parameters TOPSIS method to rank WTE incineration plant sites.•Providing managerial insights for investors and the government to manage WTE incineration plants.
•Critical review of 136 journal articles with 250 WtE case-study LCA scenarios.•Case-studies are assessed in detail with respect to critical LCA modelling aspects.•Key results and conclusions from ...the reviewed studies are highlighted.•Critical shortcomings in the studies are identified and recommendations provided.
Life cycle assessment (LCA) has been used extensively within the recent decade to evaluate the environmental performance of thermal Waste-to-Energy (WtE) technologies: incineration, co-combustion, pyrolysis and gasification. A critical review was carried out involving 250 individual case-studies published in 136 peer-reviewed journal articles within 1995 and 2013. The studies were evaluated with respect to critical aspects such as: (i) goal and scope definitions (e.g. functional units, system boundaries, temporal and geographic scopes), (ii) detailed technology parameters (e.g. related to waste composition, technology, gas cleaning, energy recovery, residue management, and inventory data), and (iii) modeling principles (e.g. energy/mass calculation principles, energy substitution, inclusion of capital goods and uncertainty evaluation). Very few of the published studies provided full and transparent descriptions of all these aspects, in many cases preventing an evaluation of the validity of results, and limiting applicability of data and results in other contexts. The review clearly suggests that the quality of LCA studies of WtE technologies and systems including energy recovery can be significantly improved. Based on the review, a detailed overview of assumptions and modeling choices in existing literature is provided in conjunction with practical recommendations for state-of-the-art LCA of Waste-to-Energy.
•The topic of energy recovery from waste by thermal treatment is reviewed.•Combustion, gasification and pyrolysis were considered.•Data about energy recovery performances were collected and ...compared.•Main limitations to high values of energy performances were illustrated.•Diffusion of energy recovery from waste in EU, USA and other countries was discussed.
The aim of this work is to identify the current level of energy recovery through waste thermal treatment. The state of the art in energy recovery from waste was investigated, highlighting the differences for different types of thermal treatment, considering combustion/incineration, gasification and pyrolysis. Also different types of wastes – Municipal Solid Waste (MSW), Refuse Derived Fuel (RDF) or Solid Refuse Fuels (SRF) and some typologies of Industrial Waste (IW) (sludge, plastic scraps, etc.) – were included in the analysis. The investigation was carried out mainly reviewing papers, published in scientific journals and conferences, but also considering technical reports, to gather more information.
In particular the goal of this review work was to synthesize studies in order to compare the values of energy conversion efficiencies measured or calculated for different types of thermal processes and different types of waste.
It emerged that the dominant type of thermal treatment is incineration associated to energy recovery in a steam cycle. When waste gasification is applied, the produced syngas is generally combusted in a boiler to generate steam for energy recovery in a steam cycle. For both the possibilities – incineration or gasification – cogeneration is the mean to improve energy recovery, especially for small scale plants. In the case of only electricity production, the achievable values are strongly dependent on the plant size: for large plant size, where advanced technical solutions can be applied and sustained from an economic point of view, net electric efficiency may reach values up to 30–31%. In small-medium plants, net electric efficiency is constrained by scale effect and remains at values around 20–24%. Other types of technical solutions – gasification with syngas use in internally fired devices, pyrolysis and plasma gasification – are less common or studied at pilot or demonstrative scale and, in any case, offer at present similar or lower levels of energy efficiency.
Despite many years of experience in the incineration of solid fuels from waste, the heterogeneity of solid fuels and their varying properties still pose a challenge for a stable and clean combustion ...in large-scale incineration plants. In modern facilities such as municipal waste incineration plants there still exists a lack of knowledge on the exact amount and calorific value of waste entering onto the grate. Based on the works of Warnecke et al. and Zwiellehner et al., in our project ‘AdOnFuelControl’, we determined the initial bulk density at the feed hopper by measuring the weight of the waste via the crane weigher and the volume via a high-performance 3D laser scanner. With the help of the determined bulk density, the lower heating value (LHV) and the compression in the feed hopper were calculated. All this information was integrated into the combustion control system, which provided a high potential for an optimized operation of the plant. In this article, six different fuels (fresh and aged municipal solid waste, refuse-derived fuel (fluff), refuse-derived fuel (fine grain), waste wood and dried, grained sewage sludge) were examined for the elemental composition, the LHV, fuel-specific parameters and the compression behaviour. In addition, initial tests with the 3D laser scanner as well as formulas for the calculation of the density in the feed hopper were presented. Based on the results of the experiments, the chosen approach seems very promising for optimized combustion control in large-scale incineration plants. As a next step, the gained knowledge and technology should be integrated in the municipal waste incineration plant.
The surge of medical waste (MW) generated during the COVID-19 pandemic has exceeded the disposal capacity of existing facilities. The timely, safe, and efficient emergency disposal of MW is critical ...to prevent the epidemic spread. Therefore, this review presents the current status of MW generation and disposal in China and analyzes the characteristics and applicability of emergency disposal technologies. The results show that movable disposal facilities can dispose of infectious MW on site, even though most of their disposal capacity is at a low level (<5 t/day). Co-disposal facilities need to be reformed completely for emergency MW disposal, in which separate feeding systems should be taken seriously. Specifically, municipal solid waste (MSW) incineration facilities have great potential to improve emergency MW disposal capacities. For hazardous waste incineration facilities, compatibility of the wastes must be matched to the composition and calorific value of the waste. As for cement kiln, MW can only be used as an alternative fuel instead of a raw material for cement. Based on the environmental risk and technical adaptability, the six emergency MW disposal technologies are recommended to be prioritized as follows: movable microwave sterilization, movable steam sterilization, movable incineration, co-incineration with hazardous waste, co-incineration with MSW and co-disposal in cement kilns. Infectious MW, especially COVID-19 MW, should be prioritized for disposal by centralized and movable disposal facilities, while non-infectious MW can be disposed of using co-disposal facilities. All stakeholders should strengthen the delicacy management of the end-of-life stage of MW, including collection, classification, packaging identification, transportation, and disposal. Currently, it is necessary for centralized disposal enterprises to follow the emergency disposal operation flowchart. From a long-term strategic perspective, making full use of regional movable and co-disposal facilities in the megacities can effectively enhance the emergency MW disposal capacity.
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•The order of priority of six emergency MW disposal technologies are recommended.•Recommendations on MW management are proposed for areas with serious epidemic.•Centralized and movable facilities should prioritize the infectious MW disposal.•Movable facilities with easy installation and operation can dispose of MW on site.•MSW incineration has great potential in enhancing emergency disposal capacity.
•The technical and economical analyses of a municipal solid waste (MSW) grate furnace with oxy-fuel incineration technology are performed.•The 25% O2 oxy-enriched incineration retains advantages in ...the isothermal combustion temperature (Ta) and flue gas loss (q2).•MSW oxy-enriched incineration retains obvious advantages and demonstrates great future prospects for MSW incineration in China.
To investigate the application prospect of MSW oxy-enriched incineration technology in China, the technical and economical analyses of a municipal solid waste (MSW) grate furnace with oxy-fuel incineration technology in comparison to co-incineration with coal are performed. The rated capacity of the grate furnace is 350tonnes MSW per day. When raw MSW is burned, the amount of pure oxygen injected should be about 14.5wt.% under 25% O2 oxy-fuel combustion conditions with the mode of oxygen supply determined by the actual situation. According to the isothermal combustion temperature (Ta), the combustion effect of 25% O2 oxy-enriched incineration (α=1.43) is identical with that of MSW co-incineration with 20% mass ratio of coal (α=1.91). However, the former is better than the latter in terms of plant cost, flue gas loss, and environmental impact. Despite the lower costs of MSW co-incineration with mass ratio of 5% and 10% coal (α=1.91), 25% O2 oxy-enriched incineration (α=1.43) is far more advantageous in combustion and pollutant control. Conventional combustion flue gas loss (q2) for co-incineration with 0% coal, 20% coal, 10% coal, 5% coal are around 17%, 13%, 14% and 15%, respectively, while that under the condition of 25% O2 oxy-enriched combustion is approximately 12% (α=1.43). Clearly, q2 of oxy-enriched incineration is less than other methods under the same combustion conditions. High moisture content presents challenges for MSW incineration, therefore it is necessary to dry MSW prior to incineration, and making oxy-enriched incineration technology achieves higher combustion temperature and lower flue gas loss. In conclusion, based on technical and economical analysis, MSW oxy-enriched incineration retains obvious advantages and demonstrates great future prospects for MSW incineration in China.
•Innovative solar integrated municipal solid waste to energy power plant proposed.•Exergoeconomic analysis, optimization and comparison with reference WtE plant.•Power exergy efficiency and heat ...exergy efficiency ratio are investigated.•Exergy efficiency and total exergy destruction cost are analyzed in optimization.
Waste to energy technology is the most promising method to deal with municipal solid waste. However, electrical efficiency of conventional waste-to-energy incineration is low due to the limits of steam turbine inlet parameters by the high moisture in municipal solid waste with low heating value. An integration of municipal solid waste incineration plant with solar thermal system was proposed and designed to increase the energy production efficiency. The integration is accomplished by increasing the steam temperature with the secondary heating by solar parabolic dish system, installed between the exit of the incineration boiler and the entrance of steam turbine. Thermodynamic and exergoeconomic performance of the integrated waste-to-energy plant is evaluated using engineering equation solver, while optimization is performed to set the optimal parameters of the system. Thermodynamic results conclude that the thermal and exergetic efficiencies of the integrated plant are 30.57% and 32.42%, while for conventional plant are only 28.35% and 26.74% respectively. Exergoeconomic analysis reveals that the exergetic cost rate of destruction for the integrated plant is 907.3 $/h and 25.61% more than the conventional design whereas, the total cost rate of the proposed system is approximately 1103 $/h. Generally, it can be concluded that the solar integrated waste to energy plant depicts great performance from a thermodynamic, economic, and environmental perspective.
•The co-gasification of food waste was compared with that of sewage sludge.•Food wastes are more favorable than sewage sludge for residue and energy output.•Two decentralized gasification-based ...disposal schemes were proposed for Singapore.•Monte Carlo simulation-based cost-benefit analysis was conducted.•The proposed schemes are financially superior to the incineration-based scheme.
The compositions of food wastes and their co-gasification producer gas were compared with the existing data of sewage sludge. Results showed that food wastes are more favorable than sewage sludge for co-gasification based on residue generation and energy output. Two decentralized gasification-based schemes were proposed to dispose of the sewage sludge and food wastes in Singapore. Monte Carlo simulation-based cost-benefit analysis was conducted to compare the proposed schemes with the existing incineration-based scheme. It was found that the gasification-based schemes are financially superior to the incineration-based scheme based on the data of net present value (NPV), benefit-cost ratio (BCR), and internal rate of return (IRR). Sensitivity analysis was conducted to suggest effective measures to improve the economics of the schemes.
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