The conversion of biomass by thermochemical means is very promising for the substitution of fossil materials in many energy applications. Given the complexity of biomass the main challenge in its use ...is to obtain products with high yield and purity. For a better understanding of biomass thermochemical conversion, many authors have studied in TG analyzer or at bed scale the individual pyrolysis of its main constituents (i.e. cellulose, hemicelluloses and lignin). Based on these studies, this original work synthesizes the main steps of conversion and the composition of the products obtained from each constituent. Pyrolysis conversion can be described as the superposition of three main pathways (char formation, depolymerization and fragmentation) and secondary reactions. Lignin, which is composed of many benzene rings, gives the highest char yield and its depolymerization leads to various phenols. The depolymerization of the polysaccharides is a source of anhydro-saccharides and furan compounds. The fragmentation of the different constituents and the secondary reactions produce CO, CO2 and small chain compounds. For temperature higher than 500°C, the residues obtained from the different constituents present a similar structure, which evolves towards a more condensed polyaromatic form by releasing CH4, CO and H2. As the aromatic rings and their substituent composition have a critical influence on the reactivity of pyrolysis products, a particular attention has been given to their formation. Some mechanisms are proposed to explain the formation of the main products. From the results of this study it is possible to predict the reactivity and energy content of the pyrolysis products and evaluate their potential use as biofuels in renewable applications.
The uncontrolled discharge of large amounts of food waste (FW) causes severe environmental pollution in many countries. Within different possible treatment routes, anaerobic digestion (AD) of FW into ...biogas, is a proven and effective solution for FW treatment and valorization. The present paper reviews the characteristics of FW, the principles of AD, the process parameters, and two approaches (pretreatment and co-digestion) for enhancing AD of food waste. Among the successive digestion reactions, hydrolysis is considered to be the rate-limiting step. To enhance the performance of AD, several physical, thermo-chemical, biological or combined pretreatments are reviewed. Moreover, a promising way for improving the performance of AD is the co-digestion of FW with other organic substrates, as confirmed by numerous studies, where a higher buffer capacity and an optimum nutrient balance enhance the biogas/methane yields of the co-digestion system.
Dynamic stabilization of an array Large-scale systems comprising one-dimensional chains and two-dimensional arrays of excited atoms held in a programmable optical lattice are a powerful platform with ...which to simulate emergent phenomena. Bluvsteinet al.built an array of up to 200 Rydberg atoms and subjected the system to periodic excitation. Under such driven excitation, they found that the array of atoms stabilized, freezing periodically into what looked like time crystals. Understanding and controlling the dynamic interactions in quantum many-body systems lies at the heart of contemporary condensed matter physics and the exotic phenomena that can occur. Science, this issue p.<related-article issue='6536' page='1355' related-article-type='in-this-issue' vol='371'>1355</related-article>
Combustion of fuels to generate energy is integral to various human activities, both domestic and industrial. However, the predominance of hydrocarbon fuel usage produces emissions containing ...pollutants that cause multiple environmental complications and risks to human health. Therefore, replacement of conventional fuels to achieve zero carbon emission is of utmost importance. In terms of carbon-free fuel, ammonia offers several advantages over hydrogen. However, its low burning velocity and high fuel NOx emissions inhibit large-scale usage. Hence, hydrogen and methane have been studied in this review as possible secondary fuels to aid ammonia combustion and address the aforementioned issues. This review starts from the suitability of ammonia fuel as energy vector in terms of physicochemical and combustion characteristics, moving through the kinetics and mechanisms of ammonia-based and ammonia-fuel combustion. The impacts and limitations of each system are also addressed, thus providing a comparison on each system. Particularly, this review assesses and discusses the advantages and mechanisms involved with secondary fuel addition to the ammonia combustion, presenting the role of key reaction differences and the change in key reaction mechanism under different conditions at the level of reaction mechanisms. Finally, this review covers future perspectives and challenges on the usage and development of ammonia-based fuels, emphasizing the maturity of ammonia-based and ammonia-fuel combustion kinetics. Herein, this work summarizes the principles of the combustion reactions of ammonia-based and ammonia-fuel systematically and serves as a theoretical reference of ammonia-fuel combustion kinetics for transitioning into future practical applications where ammonia is an important energy vector.
•Physicochemical and combustion characteristics of ammonia are summarized in detail.•Hydrogen/methane addition to ammonia combustion is discussed.•Effects on combustion speed, NOx generation and reaction kinetics are discussed.•Both hydrogen and methane are effective in improving ammonia combustion.•Future development of ammonia-based fuels is prospected.
for reducing GHG emissions and the challenges of climate change, such as “green finance”, have emerged as an approach that combines financial services and products that confront a wider range of ...sustainability issues, such as commercial pollution reduction, environmental management, improved sanitation, and environmental conservation. Therefore, our study aimed to investigate how green financing and renewable energy sources in China contribute to sustainable development. This study employs a unique methodology called panel cointegration and causality modelling to analyse the factors that led to the growth of renewable energy in China between 2005 and 2020. The results demonstrate the value of green finance development and private sector participation in localised and worldwide growth. Trademark registrations will increase by 0.487% and financial development filings by 0.144% for every 1% increase in renewable energy sources. When private sector participation is enhanced by 0.032%, trademarks and patents increase by 0.057%. Investment, trade, and human development calm these relationships. Several robustness tests support our findings. The study's empirical evidence, policymakers and environmentalists now have helpful knowledge for creating and implementing environmental projects with long-term financial advantages.
•Nexus among green finance and renewable energy were studied.•Green finance positively impacted on RE development.•Financial inclusion raised renewable energy development.•Several robustness tests were performed.
Lignocelluloses are often a major or sometimes the sole components in different waste streams from various sources such as industries, forestry, agriculture and municipalities. It represents an ...as-of-yet untapped source of fermentable sugars for significant industrial use. Many physico-chemical, structural and compositional factors hinder the hydrolysis of components present in the biomass to sugars and other organic compounds that can later be converted into fuels. During the past few years, a large number of chemical pretreatment methods including lime, acid, steam explosion, sulfur dioxide explosion, ammonia fiber explosion, ionic liquid and others have been developed for efficient pretreatment of biomass. Many pretreatment methods have shown high sugar yields i.e. more than 90% of the theoretical yield from lignocelluloses. In this review, we discuss various chemical pretreatment processes, feasibility of the processes at industrial scale in terms of the mechanisms involved, advantages, disadvantages and economic assessment. It is not possible to define the best pretreatment method as it depends on many factors such as type of lignocellulosic biomass, process parameters, environmental impact, economical feasibility, etc. However, some of these chemical pretreatments have disadvantages such as formation of inhibitory compounds especially furfural and 5-hydroxyl methyl furfural (HMF).
This paper performs Fourier cointegration and causality tests to analyze the effect of renewable energy generation, globalization, and agricultural activities on ecological footprint and carbon ...dioxide (CO2) emissions in BRIC countries for the period 1971–2016. The Fourier ADL cointegration test supports a long-run relationship between the considered variables in Brazil and China. The long-term elasticities indicate that globalization increases the pollution indicators, while renewable energy generation significantly reduces environmental pressure in China. Moreover, globalization increases CO2 emissions, while renewable energy generation improves environmental quality in Brazil. The causality results show the existence of bidirectional causality between agriculture and environmental degradation; unidirectional relationships from globalization to the ecological footprint and CO2 emissions; and renewable energy generation to the ecological indicators. Overall, these findings reveal the importance of renewable energy in combating environmental degradation. Based on the above results, renewable energy generation can significantly reduce environmental pollution in Brazil and China. However, renewable energy does not affect environmental pressure in Russia and India. Therefore, these countries should differentiate the current renewable energy generation policies to achieve their sustainable development goals.
Hybrid energy systems are being utilized for supplying electrical energy in urban, rural and remote areas to overcome the intermittence of solar and wind resources. A hybrid renewable energy system ...incorporates two or more electricity generation options based on renewable energy or fossil fuel unit. The techno-economic analysis of the hybrid system is essential for the efficient utilization of renewable energy resources. Due to multiple generation systems, hybrid system analysis, is quite complex and requires to be analyzed thoroughly. This requires software tools for the design, analysis, optimization, and economic viability of the systems. In this paper, 19 softwares with their main features and current status are presented. The softwares studied are HOMER, Hybrid2, RETScreen, iHOGA, INSEL, TRNSYS, iGRHYSO, HYBRIDS, RAPSIM, SOMES, SOLSTOR, HySim, HybSim, IPSYS, HySys, Dymola/Modelica, ARES, SOLSIM, and HYBRID DESIGNER. The research work related to hybrid systems carried out using these softwares at different locations worldwide is also reviewed. The main objective of the paper is to provide the current status of these softwares to provide basic insight for a researcher to identify and utilize suitable tool for research and development studies of hybrid systems. The capabilities of different softwares are also highlighted. The limitations, availability and areas of further research have also been identified.
Catalytic reduction of CO into fuels and fine chemicals Modak, Arindam; Bhanja, Piyali; Dutta, Saikat ...
Green chemistry : an international journal and green chemistry resource : GC,
07/2020, Letnik:
22, Številka:
13
Journal Article
Recenzirano
With the progressive increase in atmospheric CO
2
over the years and owing to its potential environmental threat, researchers have focused their attention on the fruitful utilization of CO
2
into ...value-added chemicals and feedstocks. Although CO
2
conversion reactions are intensively studied through several electrochemical, photochemical and photo-electrochemical pathways, chemical reduction of CO
2
is more challenging to achieve due to the involvement of breaking of high energy C&z.dbd;O bonds without any applied potential together with the accomplishment of green chemistry perspectives. Considerable progress in the chemical reduction of CO
2
in the presence of reducing agents over homogeneous and heterogeneous catalysts has been achieved over the years. However, this technology has several pitfalls to overcome before it can be utilized in large scale industrial processes. We show here the recent progress in CO
2
reduction to essential fuels CO, CH
3
OH, CH
3
CH
2
OH, HCO
2
H, CH
4
, dimethylether (DME), dimethylcarbonate (DMC) and lower hydrocarbons as well as valuable chemicals
via
nucleophilic addition reactions. We also emphasize the direct conversion of CO
2
from ultra-diluted sources like ambient air as a possible roadmap to solve carbon emission problems from the real world. The entire discussion is divided into two parts where in the first part we summarize several homogeneous catalytic processes involving the nucleophilic addition of CO
2
, resulting in C-C and C-H bond formation leading to the synthesis of 2-oxazolidinones, aminals, terminal carboxylated products and indolelactone derivatives that are potentially sound for the pharmaceutical industry. Other reduction products, such as methane, methanol, and methoxides, are also listed using Frustrated Lewis Pairs (FLP) as catalysts. The second part extensively highlights heterogeneous catalysts to reduce CO
2
with H
2
. However, significant efforts are still needed to develop active, selective and stable catalysts on a pilot plant scale by judicial consideration of the thermodynamics and kinetics of the reactions. CO
2
reduction can proceed over a range of immobilized metallic nanoparticles on inorganic supports (CeO
2
, Al
2
O
3
, TiO
2
etc
.) and nanostructured porous frameworks (zeolites, porous polymers, mesoporous silica). Thus, thorough investigation on the reaction mechanism of the overall process involving different active sites is necessary. Primarily, this review brings together the major advancements made in the CO
2
reduction processes together with a focus on the utility and challenges in achieving the activation of the CO
2
molecule.
Catalytic reduction of CO
2
is very challenging from both economics and green chemistry perspectives. This critical review highlights major advancements made in the CO
2
reduction processes and their future challenges.
