The 2020 plasma catalysis roadmap Bogaerts, Annemie; Tu, Xin; Whitehead, J Christopher ...
Journal of physics. D, Applied physics,
10/2020, Volume:
53, Issue:
44
Journal Article
Peer reviewed
Open access
Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons ...or oxygenates, and NH3 synthesis. Other applications are already more established, such as for air pollution control, e.g. volatile organic compound remediation, particulate matter and NOx removal. In addition, plasma is also very promising for catalyst synthesis and treatment. Plasma catalysis clearly has benefits over 'conventional' catalysis, as outlined in the Introduction. However, a better insight into the underlying physical and chemical processes is crucial. This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling. The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment. Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial. All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges.
•AD of food waste is promising but has not yet been widely applied.•The quantity, composition, and CH4 potential of different food wastes are summarized.•Co-digestion with animal manure and sewage ...sludge are practical options.•Micronutrients supplementation are needed for food waste only digesters.•Control of foaming and improved process design are required.
The disposal of large amounts of food waste has caused significant environmental pollution and financial costs globally. Compared with traditional disposal methods (i.e., landfilling, incineration, and composting), anaerobic digestion (AD) is a promising technology for food waste management, but has not yet been fully applied due to a few technical and social challenges. This paper summarizes the quantity, composition, and methane potential of various types of food waste. Recent research on different strategies to enhance AD of food waste, including co-digestion, addition of micronutrients, control of foaming, and process design, is discussed. It is envisaged that AD of food waste could be combined with an existing AD facility or be integrated with the production of value-added products to reduce costs and increase revenue. Further understanding of the fundamental biological and physicochemical processes in AD is required to improve the technology.
This review aims at summarizing the literature for the coupling of the biological process of anaerobic digestion (AD) with one of three thermal processes: gasification (Gs), pyrolysis (Py), and ...hydrothermal carbonization (HTC). These thermal processes are investigated as pre and/or post treatments for AD, aiming at reducing its main drawbacks. The different cases are considered separately, based on the thermal treatment that is coupled with the AD process: AD-Gs, AD-Py, and AD-HTC. For each group, up to three sub-cases are discussed: the thermal treatment of the digestate, the use of char from the thermal treatment as stabilizer and enhancer in the AD reactor, and the AD of the aqueous products of the thermal treatment (this last case is not available with Gs). When possible, the result of the different researches for each configurations are grouped for comparison. Finally, an overview of the most promising future research investigations is given.
•Biological and thermo-chemical processes towards the bio-refinery concept.•Anaerobic Digestion coupled with Gasification.•Anaerobic Digestion coupled with Pyrolysis.•Anaerobic Digestion coupled with Hydro-Thermal Carbonization.•Main challenges, points of interest and suggested future research focus.
Municipal solid waste (MSW) management is becoming a serious issue in all over the world. Anaerobic digestion (AD) is one of the technologies to convert that waste into useful form of energy. But ...megacities like Singapore having limited resources, cannot fulfill the cow dung or other animal manure requirements in AD. Therefore there is a need to study critically the operating parameters and also the pretreatment technologies available for treating the substrate so that one can get the maximum output with limited input. To fulfill the need, the present paper deals with the review of various operating parameters and their effects on AD. This paper also reviews different pretreatment methods including mechanical, thermal, chemical and biological methods to improve the effectiveness of AD of MSW.
Gaussian processes (GPs) provide a principled, practical, probabilistic approach to learning in kernel machines. GPs have received increased attention in the machine-learning community over the past ...decade, and this book provides a long-needed systematic and unified treatment of theoretical and practical aspects of GPs in machine learning. The treatment is comprehensive and self-contained, targeted at researchers and students in machine learning and applied statistics.The book deals with the supervised-learning problem for both regression and classification, and includes detailed algorithms. A wide variety of covariance (kernel) functions are presented and their properties discussed. Model selection is discussed both from a Bayesian and a classical perspective. Many connections to other well-known techniques from machine learning and statistics are discussed, including support-vector machines, neural networks, splines, regularization networks, relevance vector machines and others. Theoretical issues including learning curves and the PAC-Bayesian framework are treated, and several approximation methods for learning with large datasets are discussed. The book contains illustrative examples and exercises, and code and datasets are available on the Web. Appendixes provide mathematical background and a discussion of Gaussian Markov processes.
It is hard to predict wind power with high-precision due to its non-stationary and stochastic nature. The wind power has developed rapidly around the world as a promising renewable energy industry. ...The uncertainty of wind power brings difficult challenges to the operation of the power system with the integration of wind farms into power grid. Accurate wind power prediction is increasingly important for the stable operation of wind farms and the power grid. This study is combined support vector machine and improved dragonfly algorithm to forecast short-term wind power for a hybrid prediction model. The adaptive learning factor and differential evolution strategy are introduced to improve the performance of traditional dragonfly algorithm. The improved dragonfly algorithm is used to choose the optimal parameters of support vector machine. The effectiveness of the proposed model has been confirmed on the real datasets derived from La Haute Borne wind farm in France. The proposed model has shown better prediction performance compared with the other models such as back propagation neural network and Gaussian process regression. The proposed model is suitable for short-term wind power prediction.
The flowchart of improved dragonfly algorithm. Display omitted
•An IDA-SVM model is proposed for short-term wind power forecasting.•The learning factor and differential evolution strategy are introduced in IDA.•The IDA is used to optimize the parameters of SVM.•The predicted results show that the IDA-SVM has better prediction accuracy.
Anaerobic digestion (AD) is a biological process that can convert organic substrates to biogas in the absence of oxygen. The AD process has been practiced for centuries; however, it is still a ...research focus in contemporary literature. This mini-review selected papers published in 2015 and summarized the improvement and technological advancement and revealing current research and development trends for the biogas from AD process. A discussion on the challenges and prospects for developing improved AD technologies is provided.
•Recent R&D works for biogas and anaerobic digestion process were reviewed.•Substrates, reactors, treatments, operation and system analysis were covered.•Research focuses and ways forward for AD process were discussed.
•Freeze and thaw and drying pre-treatments preserve the carbon for future processing.•Grinding pre-treatment of FW improves the surface property and bio-accessibility.•Combined grinding and thermal ...pre-treatments improves the digestibility.•Energy-economics of integrated FW pre-treatment require to be established.
Food waste (FW) management by biological process is more attractive and eco-friendly approach than thermo-chemical conversion or landfilling. However, FW composition and physico-chemical and biological characteristics affect the overall biological process in terms of product yield and degradation rate. To overcome this major bottle-neck, the pretreatment of FW is proposed. Therefore this review aims to provide a comprehensive summary of the importance of pretreatment of FW with respect to FW management by anaerobic digestion (AD) and dark fermentation (DF). It also reviews the existing knowledge gaps and future research perspectives for better integration of FW pretreatments for AD and DF, which should include (i) the preservation of carbon mass through freeze and thaw, or drying; and (ii) improve the carbon accessibility through particle size reduction and thermal pretreatments for high-rate bioenergy recovery.
This review examines the prospects of a decentralised hybrid rainwater-greywater system to simultaneously alleviate water scarcity and address technical, environmental, and cost constraints. This ...includes (1) a review on the physicochemical and microbiological characteristics of rainwater and greywater to determine the necessary treatment options; (2) a review of individual components and potential treatment trains for hybrid systems; and (3) an evaluation of configurations for hybrid systems. The literature review reveals that both untreated rainwater and greywater are highly variable in quality and quantity, and so an equalisation basin is proposed to normalise influent into a hybrid system. Both rainwater and greywater should not be reused without treatment due to the presence of pathogens such as Aeromonas, Salmonella, Pseudomonas, and Staphylococcus. Based on the literature, hybrid systems are categorised under three configurations: (a) separate treatments of rainwater and greywater; (b) rainwater reused in washing machines prior to reuse as greywater; and (c) combined treatment of rainwater and greywater. In all three designs, rainwater requires only first-flush diversion and disinfection. Combined rainwater-greywater mixtures should be treated as greywater. Greywater requires chemical, biological, and physical treatment to meet non-potable reuse standards. Chemical processes are effective at removing solids, organics, and surfactants in light greywater, whereas aerobic biological processes are effective at organics removal in mixed and dark greywaters with high organic strength. Physical processes, particularly membrane filtration, are recommended for polishing effluents from chemical or biological treatment as membranes foul frequently and are costly. Subsequently, a combination of ozone or UV with chlorine is recommended to eradicate chlorine-resistant Cryptosporidium oocysts from hybrid rainwater-greywater systems and prevent microbial regrowth.
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•Raw greywater contains more organics, solids, and pathogens than rainwater.•Hybrid rainwater-greywater system configurations are categorised into 3 groups.•Identified potential treatment trains for hybrid rainwater-greywater systems.
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•Hydrolysis affects the process yield of anaerobic digestion of lignocellulosics.•Microbial lignin degradation limits anaerobic bioconversion of lignocellulosics.•Studies linking ...microbiology and process engineering are important for hydrolysis.•Biological pretreatment, co-digestion, and inoculation can enhance hydrolysis.•Mimicking natural microbial ecosystems is a promising option to improve hydrolysis.
Lignocellulosic biomass is the most abundant renewable bioresource on earth. In lignocellulosic biomass, the cellulose and hemicellulose are bound with lignin and other molecules to form a complex structure not easily accessible to microbial degradation. Anaerobic digestion (AD) of lignocellulosic biomass with a focus on improving hydrolysis, the rate limiting step in AD of lignocellulosic feedstocks, has received considerable attention. This review highlights challenges with AD of lignocellulosic biomass, factors contributing to its recalcitrance, and natural microbial ecosystems, such as the gastrointestinal tracts of herbivorous animals, capable of performing hydrolysis efficiently. Biological strategies that have been evaluated to enhance hydrolysis of lignocellulosic biomass include biological pretreatment, co-digestion, and inoculum selection. Strategies to further improve these approaches along with future research directions are outlined with a focus on linking studies of microbial communities involved in hydrolysis of lignocellulosics to process engineering.
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