Hydrothermal carbonization of municipal waste streams.
14 Jun 2011-Environmental Science & Technology (American Chemical Society)-Vol. 45, Iss: 13, pp 5696-5703
TL;DR: The composition of the produced hydrochar suggests both dehydration and decarboxylation occur during carbonization, resulting in structures with high aromaticities, and process energetics suggest feedstock carbonization is exothermic.
Abstract: Hydrothermal carbonization (HTC) is a novel thermal conversion process that can be used to convert municipal waste streams into sterilized, value-added hydrochar. HTC has been mostly applied and studied on a limited number of feedstocks, ranging from pure substances to slightly more complex biomass such as wood, with an emphasis on nanostructure generation. There has been little work exploring the carbonization of complex waste streams or of utilizing HTC as a sustainable waste management technique. The objectives of this study were to evaluate the environmental implications associated with the carbonization of representative municipal waste streams (including gas and liquid products), to evaluate the physical, chemical, and thermal properties of the produced hydrochar, and to determine carbonization energetics associated with each waste stream. Results from batch carbonization experiments indicate 49–75% of the initially present carbon is retained within the char, while 20–37% and 2–11% of the carbon is ...
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TL;DR: This review will introduce to the reader the most recent and important progress regarding the production of sustainable carbon materials, whilst also highlighting their application in important environmental and energy related fields.
Abstract: Carbon-based structures are the most versatile materials used in the modern field of renewable energy (i.e., in both generation and storage) and environmental science (e.g., purification/remediation). However, there is a need and indeed a desire to develop increasingly more sustainable variants of classical carbon materials (e.g., activated carbons, carbon nanotubes, carbon aerogels, etc.), particularly when the whole life cycle is considered (i.e., from precursor "cradle" to "green" manufacturing and the product end-of-life "grave"). In this regard, and perhaps mimicking in some respects the natural carbon cycles/production, utilization of natural, abundant and more renewable precursors, coupled with simpler, lower energy synthetic processes which can contribute in part to the reduction in greenhouse gas emissions or the use of toxic elements, can be considered as crucial parameters in the development of sustainable materials manufacturing. Therefore, the synthesis and application of sustainable carbon materials are receiving increasing levels of interest, particularly as application benefits in the context of future energy/chemical industry are becoming recognized. This review will introduce to the reader the most recent and important progress regarding the production of sustainable carbon materials, whilst also highlighting their application in important environmental and energy related fields.
935 citations
TL;DR: A systematic and critical review of the production of activated carbon from hydrochars is presented in this paper, where the current knowledge gaps and challenges involved in the hydrothermal carbonization of biomass waste are critically evaluated with suggestions for further research.
812 citations
Cites background from "Hydrothermal carbonization of munic..."
...Characterization and applications of hydrothermally carbonized chars obtained from different biomass sources have been discussed in literature [12,14,16,60,105]....
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...Numerous studies on hydrothermal carbonization have been carried out to investigate the effects of various operating parameters on the quality and yield of products (solid char, liquid and gas) [11,12,16,52,53,59–65]....
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...The conversion of alkaline waste appears to be largely influenced by decarboxylation whereas dehydration dominates in the case of acidic feedstock [12]....
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...reported the conversion of municipal solid waste to hydrochar and its feasibility to operate at larger scale [12]....
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...Carbonization temperature is dependent on the type of starting materials and its decomposition temperature; a range of 150–350 C is typically employed [2,10–15]....
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TL;DR: In this article, the authors provide an overview on recently developed carbon material technology synthesised from the hydrothermal carbonisation (HTC) approach, with a particular focus on the carbon formation mechanism, perspectives on large scale production, nanostructuring, functionalisation and applications.
Abstract: This perspective review paper provides an overview on recently developed carbon material technology synthesised from the hydrothermal carbonisation (HTC) approach, with a particular focus on the carbon formation mechanism, perspectives on large scale production, nanostructuring, functionalisation and applications. Perceptions on how this technology will be developed especially with regard to application fields where the use of HTC-derived materials could be extended will also be introduced and discussed.
759 citations
TL;DR: In this paper, the authors presented the critical hydrothermal parameters of hydrothermal carbonization, including temperature, residence time, heating rate, reactant concentration, and aqueous quality.
Abstract: Hydrothermal carbonization (HTC) is a thermochemical conversion technique which is attractive due to its ability to transform wet biomass into energy and chemicals without predrying. The solid product, known as hydrochar, has received attention because of its ability to prepare precursors of activated carbon in wastewater pollution remediation, soil remediation applications, solid fuels, and other carbonaceous materials. Besides the generally lignocellulose biomass used as sustainable feedstock, HTC has been applied to a wide range of derived waste, including sewage sludge, algae, and municipal solid waste to solve practical problems and generate desirable carbonaceous products. This review presented the critical hydrothermal parameters of HTC, including temperature, residence time, heating rate, reactant concentration, and aqueous quality. The chemical reaction mechanisms involved in the formation of hydrochar derived from single components and representative feedstock, lignocellulose, and sludge termed as N-free and N-rich biomass, were elucidated and summarized to better understand the hydrochar formation process. Specifically, hydrochar physicochemical characteristics such as surface chemistry and structure were investigated. Current knowledge gaps, and new perspectives with corresponding recommendations were provided to further exploit the great potential of the HTC technique and more practical applications for hydrochar in the future.
707 citations
TL;DR: In this article, the authors used the hydrothermal carbonization (HTC) process to convert sewage sludge into clean solid fuel without prior drying, and evaluated the fuel characteristics and combustion behaviors of hydrochars.
706 citations
Cites background from "Hydrothermal carbonization of munic..."
...However, an immiscible liquid-phase was observed during HTC of municipal waste streams at 250 C [14], which indicated that hydrothermal liquefaction occurred and lower carbonization temperature was desired....
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...Currently, many biomass substrates, including cellulose [11], microalgae [12,13], anaerobically digested maize silage [8], municipal solid waste [14–16], distiller’s grains [17], and black liquor [18], have been applied in HTC to gain fuels or materials....
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...This indicates that VM was also converted into other products, such as CO2 or liquid [14,29]....
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...The evolved gas is small and mainly consists of carbon dioxide [14]....
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TL;DR: In this article, a review summarizes knowledge about the chemical nature of this process from a process design point of view, including reaction mechanisms of hydrolysis, dehydration, decarboxylation, aromatization, and condensation polymerization.
Abstract: Hydrothermal carbonization can be defined as combined dehydration and decarboxy lation of a fuel to raise its carbon content with the aim of achieving a higher calorific value. It is realized by applying elevated temperatures (180–220°C) to biomass in a suspension with water under saturated pressure for several hours. With this conversion process, a lignite-like, easy to handle fuel with well-defined properties can be created from biomass residues, even with high moisture content. Thus it may contribute to a wider application of biomass for energetic purposes. Although hydrothermal carbonization has been known for nearly a century, it has received little attention in current biomass conversion research. This review summarizes knowledge about the chemical nature of this process from a process design point of view. Reaction mechanisms of hydrolysis, dehydration, decarboxylation, aromatization, and condensation polymerization are discussed and evaluated to describe important operational parameters qualitatively. The results are used to derive fundamental process design improvements. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd
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