The transformation of the energy systems encompasses technological, societal, cultural, economic, and environmental aspects and calls for a more important role for citizens and communities. Bioenergy ...systems are subjects to legal, technical, environmental, economic, and social settings. At the regional level, bioenergy can incorporate agricultural traditions and offer waste-management solutions. Many are the stakeholders, with different perceptions and sometimes, conflictual interests. This study is a multidisciplinary, comprehensive review of recently published papers, on legal, technical, economic, and environmental layers of the bioenergy. It highlights the role of bioenergy in the transition to a Circular waste-based Bioeconomy. Three dimensions of sustainability (environmental, economic, and social) were discussed and some thermodynamic (energy, exergy, emergy) and environmental indicators applied to bioenergy systems, were cited. Findings conclude that in the context of Circular Bioeconomy, global bioenergy sector may face challenges, due to the new demand for biomaterials from the same sources. Bioenergy sustainable pathways should be selected at the base of high efficiency, towards closing loops and in the concept of cascade and integrated biorefineries. At the regional level, bioenergy systems may be integrated with the cascade biorefinery models or can offer waste management solutions by stand-alone, tailor-made decentralized systems. In redesigning the bioenergy sector, local knowledge, public health, and community's resilience should not be neglected, while social-environmental benefits should be considered in addressing the viability of bioenergy plants. Social acceptance can be improved by a better understanding of the scientific and technical issues and by developing a broader consciousness of the planet and life.
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•The study is a multidisciplinary, comprehensive review of recent published papers.•Legal, environmental, technical, economic, and social settings of bioenergy were reviewed.•In the context of Circular Bioeconomy biomass conversion must retain a high efficiency.•Bioenergy can be integrated in the cascade biorefinery and/or offer waste management solutions.•Human health, local identity and culture are important in meeting sustainable transitions.
•The high output of MSS highlights the need for alternative routes of valorization.•Evaluation of 3 sludge-to-energy valorisation methods through SWOT analysis.•Pyrolysis is an energy and material ...recovery process resulting to ‘zero waste’.•Identification of challenges and barriers for MSS pyrolysis in Greece was investigated.•Adopters of pyrolysis systems face the challenge of finding new product markets.
For a sustainable municipal sewage sludge management, not only the available technology, but also other parameters, such as policy regulations and socio-economic issues should be taken in account. In this study, the current status of both European and Greek Legislation on waste management, with a special insight in municipal sewage sludge, is presented. A SWOT analysis was further developed for comparison of pyrolysis with incineration and gasification and results are presented. Pyrolysis seems to be the optimal thermochemical treatment option compared to incineration and gasification. Sewage sludge pyrolysis is favorable for energy savings, material recovery and high added materials production, providing a ‘zero waste’ solution. Finally, identification of challenges and barriers for sewage sludge pyrolysis deployment in Greece was investigated.
Wastewater treatment leads to an increase in sewage sludge production. Sewage sludge consists, in general, of non-toxic organic matter and therefore can be utilized as a biomass resource for energy ...production. Energy recovery from sewage sludge via thermochemical valorization processes seems of great potential. Processes’ products can be used as bio-fuels, while minimization of the environmental impacts can be also achieved. In particular, wet sewage sludge pyrolysis-partial gasification at high temperatures and especially gasification give a new perspective for hydrogen-rich fuel gas production. Co-processing of sewage sludge with biomass improves the fuel's characteristics and enhances the processes efficiency. In addition, blends of sewage sludge with biomass contribute in diluting the inorganic and toxic compounds. Towards that direction, algae production using wastewater resources and then to be used for biofuels production seems a sustainable solution that is the reason why exploitation of such a material through thermochemical processes is under intensive discussion.
The European Union has made progress in dealing with municipal wastewater in individual countries and as a corporate entity. However, it intends to make still further and substantial progress over ...the next 15 years. Currently, the most widely available options in the EU are the agriculture utilization, the waste disposal sites, the land reclamation and restoration, the incineration and other novel uses. The selection of an option on a local basis reflects local or national, cultural, historical, geographical, legal, political and economic circumstances. The degree of flexibility varies from country to country. In any case sludge treatment and disposal should always be considered as an integral part of treatment of wastewater. There is a wide range of other uses for sludge, which exploit its energy or chemical content, namely the thermal processes. The present paper sought to review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.
The need for clean and environmental friendly fuels is leading the world to the production of biofuels and replacing conventional fuels by them. Second generation biofuels derived from ...lignocellulosic feedstocks tackle the drawbacks posed by the so-called first generation ones regarding feedstock availability and competition with the food industries. Thermochemical conversion of biomass to biofuels is a promising alternative route relying on well-established technologies including gasification and the Fischer–Tropsch synthesis. The conjunction of these processes creates a pathway through which the production of biofuels is sustainable. However, the multiple interactions between the processing steps greatly increase the difficulty in the accurate design of such processes. Detailed process modelling and optimization studies combined with process integration methods are necessary to demonstrate an effective way for the exploitation of these interactions. The aim of this work is to present and analyze the thermochemical conversion of biomass to second generation liquid biofuels as well as to indicate the emerging challenges and opportunities of the application of process integration on such processes towards innovative and sustainable solutions concerning climate concerns and energy security.
A review of the production of activated carbons from agricultural residues is presented. The effects of various process parameters on the pyrolysis stage are reviewed. Influences of activating ...conditions, physical and chemical, on the active carbon properties are discussed. Under certain process conditions several active carbons with BET surface areas, ranging between 250 and 2410
m
2/g and pore volumes of 0.022 and 91.4
cm
3/g, have been produced. A comparison in characteristics and uses of activated carbons from agricultural residues with those issued from tires, and commercial carbons, have been made. A review is carried out of the reaction kinetic modelling, applied to pyrolysis of agricultural wastes and activation of their pyrolytic char.
A key element in the design of sustainable pyrolysis processes is the thermal degradation kinetics of biomass. In this work, pyrolysis tests for cardoon (
Cynara carduculus) stems and leaves were ...performed in a non-isothermal thermogravimetric analyzer (TGA) in order to determine the thermal degradation behavior of both stems and leaves. The kinetic parameters of the process were evaluated using three different kinetic models, the independent parallel reaction model, KAS and OFW iso-conversional model. Good agreement with the experimental TGA data was observed for all models, the best being with the independent parallel reaction model. A variance in the activation energy with conversion was observed when the KAS and OFW models were employed, which reveals that the pyrolysis of cardoon progresses through more complex and multi-step kinetics.
Olive-seed waste residue char was employed as the precursor for the production of activated carbons with KOH activation. The effects of activation time and activation temperature on porosity of the ...prepared carbons were studied. The products were characterized by N
2 adsorption at 77
K, using the BET,
α
s and Dubinin–Radushkevich methods while the adsorption capacity from liquid phase was demonstrated by the isotherms of methylene blue adsorption from aqueous solutions. In comparison with the commercial grade carbons, the activated carbons from olive-seed waste residue showed considerably higher surface areas and can be characterized as “super-activated carbons”. The pores of the produced carbons are composed of micropores at the early stages of activation and of both micropores and mesopores at the late stages. Surface area and the pore volume were found to increase with the degree of burn-off, i.e. the activation time and temperature. Methylene blue removal capacity appeared to be comparable to commercial products and even higher at high degrees of activation.
This study aims to look at waste-to-energy (tertiary recycling) of post-consumer textile waste, based on a literature review. Because textiles are mostly made of cotton and polyester, which are ...carbon and energy sources, they can potentially be converted thermochemically into fuels and biocarbon. The critical parameters determining thermal recycling are summarized and discussed with a focus on pyrolysis, gasification, and torrefaction. For cotton and polyester mixtures, torrefaction presents a low environmental impact and an energy-dense fuel that can be used in cogeneration systems, reducing the energy requirements of these processes by 50–85%. Catalytic pyrolysis of cotton textile waste yields to a high conversion (90 wt%), a liquid fuel of high yields (35–65 wt%), and biocarbon (10–18 wt%), providing carbon and energy closure loops. However, pyrolysis is energy-intensive (T > 500 °C) and produces hazardous chemicals from the conversion of PET, nylon, and polyacrylonitrile. Gasification can handle many types of textile waste, but it needs continuous monitoring of the emissions. More research is needed to overcome existing limitations, LCA and sustainability assessment are required for the thermal recycling processes in order to estimate their future-proofing and sustainability. For the transition to a circular economy, consumers' awareness of resources limits and sustainable use is pivotal to change purchasing behavior and achieve a recycling thinking.
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•Post-consumer textile waste is still disposed in landfills.•Torrefaction is suggested for cotton and polyester mixture textile waste.•Catalytic pyrolysis is suggested for cotton textile waste.•Gasification can handle various textile waste, but it needs environmental monitoring.•Recycling methods and social behavior are interdepended.
This paper presents the essential features of an efficient and environmentally attractive pyrolysis for used tyres valorisation with energy and material recovery. The problem of tyres management ...strongly affects not only the environmental protection but even the resources maintenance, since problems related to the depletion of resources, energy demand and waste management, are strictly connected and required an integrated approach. A general guideline for EU member states, aims to reach a zero post-consumer amount of tyre disposal in landfills before the end of 21st century, to optimize and expand the already well studied ways of their treatment and find new ones, in order to accomplish a balance between economy and environmental protection. In this context, thermal treatment of end of life tyres could play a relevant role for the recovery of resources (matter and/or energy). During the past 10–15 years, several fundamental and applied studies showed that if carefully controlled, tyre pyrolysis can produce a number of valuable products. The final destination of the pyrolysis solid residue largely influences the industrial applications of pyrolysis.
