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Abstract The combination of biomass gasification with fuel cells, especially high temperature Solid Oxide Fuel Cells (SOFCs) promises sustainable and highly efficient (decentralized and modular) energy conversion systems. This review encompasses the components of biomass integrated gasification–SOFC technology including biomass characteristics, the thermochemical conversion in gasifiers and the factors affecting the gasification process, the cleaning technologies for raw producer gas and its conditioning and finally the integration of gasifier with SOFCs. The influence of impurities present in biomass producer gas such as particulates, tar, H 2 S, HCl and alkali compounds based on recent experimental studies and their tolerance limits towards SOFCs are presented. Even though analysis based on the probable tolerance limits of impurities towards SOFCs and a comprehensive overview of the cleaning technologies for producer gas impurities indicate that producer gas cleaning at various temperatures using current technologies to meet SOFC requirements is possible, more experimental studies are still needed to acquire the detailed information on the tolerance limits of impurities for SOFCs. The recent theoretical modeling and experimental studies of biomass integrated gasification–SOFC systems are also presented.

Renewable energy has become more popular since it is cost-effective and more efficient than conventional energy sources. Biomass-based renewable energy is primarily used in emerging economies to ensure environmental sustainability. This study examines the asymmetric correlation between biomass energy consumption and CO2 emissions in the top-10 biomass energy consumer countries (Brazil, Canada, Thailand, China, Italy, India, Germany, USA, UK, and Japan). A new approach "Quantile-onQuantile (QQ)" is employed by utilizing the data from 1991 to 2018. Biomass energy consumption, with the exception of Thailand, significantly mitigates CO2 emissions at various quantiles in selected countries. As a robustness check, we used the quantile regression test, whose findings are consistent with the outcomes from the quantile-on-quantile method. However, the degree of asymmetry in the biomass energy-CO2 nexus varies by country, necessitating extra attention and government vigilance when developing biomass energy and environmental policies.

Abstract Hydrogen is considered a potential game changer for world energy systems and a solution to climate change concerns, as it generates zero waste and it is suited for power generation and transportation. Despite its several advantages, there are significant technical challenges in deploying a stable hydrogen economy including improving its process efficiencies, lowering production costs, maintaining cost-effective transmission and distribution, and exploiting inexpensive and sustainable feedstocks. In this context, a detailed study was conducted to analyze the production sources, technologies, storage and transport systems, and global potential exportable feedstocks to produce hydrogen. A comprehensive analysis of current hydrogen production technologies with their energy efficiencies and hydrogen selling prices was reported in this study. Various hydrogen production technologies with their capital investments and CO2 emissions were also presented. Potential feedstocks for hydrogen production were identified and analyzed through a product space model, which characterizes a network of global exportable products based on their similarities and productive knowledge. It was established that the hydrogen production feedstocks and sources currently used are primarily available in six countries: the United States of America, France, Russia, Sweden, the Netherlands, and Spain. Broadly, the results revealed that the United States of America and Russia shared the highest hydrogen feedstock exports, indicating a higher probability of hydrogen production in these countries. Except for Russia, all the studied countries fell in the most desired quadrant, indicating that they can move in all product space directions to exploit unexplored hydrogen feedstocks for better sustainable economic growth.

Abstract This study presents an overview of footprints as defined indicators that can be used to measure sustainability. An overview of the definitions and units of measurement associated with environmental, social, and economic footprints is important because the definitions of footprints vary and are often expressed unclearly. Composite footprints combining two or more individual footprints are also assessed. These combinations produce multi-objective optimisation problems. Several tools for footprint(s)' evaluation are presented, including some of the numerous carbon footprint calculators, available calculators for other footprints, some ecological footprints-based, graph-based, and mathematical programming tools. A comprehensive overview is offered of footprint-based sustainability assessment.

The upsurge in higher education is considered a key determinant for enhancing green growth. Moreover, ICT development is also the main catalyst of green growth. This research explores the role of higher education and ICT on green growth for China from 1995 to 2020. The study employs auto-regressive distributive lag (ARDL) approach for short-run and long-run estimates of green growth. The effect of higher education and ICT on green growth is significantly positive in the long run and short run. The outcomes of the empirical models reveal that financial inclusion is positively associated with green growth in both long run and short run. Moreover, renewable energy consumption is found to have a positive impact on green growth. The findings thus point to the need for policies that promote human capital and ICT infrastructure as a way of accelerating green growth.

The relationship between exchange rate volatility (ERV) and other macroeconomic factors, including trade flows, domestic production, inflation, money demand, and economic growth, has remained a topic of a large number of studies in international finance. However, the research question that the past empirics have overlooked is whether ERV has any role in helping an emerging economy like China in its journey toward a renewable energy transition. To answer this question, this analysis intends to scrutinize the nexus between ERV and renewable energy investment (REI) in China over 1991Q1-2021Q4. Moreover, due to the asymmetric behavior of ERV, we have based our analysis on the asymmetric assumption. For analyzing the short and long-run impacts of ERV on REI in China, we used the linear autoregressive distributed lag (ARDL) and nonlinear ARDL methods. In the long term, the ARDL model predicts that stricter environmental policies and higher GDP will lead to more investment in renewable energy. As far as the nonlinear model is concerned, the long-term negative change in ERV does not affect REIs, whereas a long-term positive change in ERV reduces such investments. Likewise, unfavorable short-term exchange rate shocks encourage REI while positive short-term shocks discourage such development. Moreover, investment in renewable energy is bolstered by GDP, environmental policy strictness, and financial development, but is dampened by CO2 emissions in the short term in both models. On the basis of these results, we suggest that policymakers should consider implementing measures to stabilize exchange rates to promote investment in renewable energy.

The present study investigates the effect of public–private partnership investment in energy and renewable energy consumption on carbon dioxide (CO2) emissions, taking into account the critical role of economic growth and trade openness in Pakistan from 1992 to 2019. The linear and nonlinear autoregressive distributed lag models are employed to check the co-integration link between dependent and independent variables, further estimate short-run and long-run associations, and examine the symmetric and asymmetric effects of public–private partnership investment in energy on CO2 emissions in Pakistan. The empirical findings show that public–private partnership investment in energy reduces environmental quality by increasing CO2 emissions. Similarly, economic development and trade openness harms the atmosphere by raising CO2 emissions. On the other hand, renewable energy consumption significantly negatively affects CO2 emissions. In addition, the findings also authenticate the asymmetric link between public–private partnership investment in energy and the environment, as CO2 emissions are caused mainly by positive shocks in public–private partnership investment in energy in the short and long run. This study proposes financing renewable energy projects through public–private partnership is needed for an environmentally friendly future.

Oxides of nitrogen are among the most dangerous emissions to human health and to the environment. In European nations, road transportation contributes to approximately 40% of emissions of oxides of nitrogen with the dominant share coming from passenger and freight transport. To help mitigate emissions of oxides of nitrogen, the European Union (EU) has implemented vehicular emissions standards. This paper studies the effect of EU vehicular emissions standards on per capita emissions of oxides of nitrogen in European nations during the period 2000 to 2017, both for on-road vehicular emissions and at the economy level. To do this, pollution is modelled as a byproduct of economic production. After controlling for economic growth, historical per capita levels of emissions of oxides of nitrogen, and a series of geographic and technological factors, it is determined that the vehicular emissions standards put in place by the EU decrease per capita levels of emissions of oxides of nitrogen. More precisely, reducing the heavy duty emissions standard by 1 g/kWh leads to as much as a 7% reduction in per capita on-road emissions of oxides of nitrogen. Reducing the passenger vehicle emissions standards for both diesel and gasoline engines enhances this effect, resulting in an even greater reduction in per capita emissions of oxides of nitrogen. These results further suggest that any rebound effect taking place is outweighed by the reduction in emissions of oxides of nitrogen from lowering emissions standards.

An anaerobic moving bed membrane bioreactor (AnMBMBR) fed with synthetic domestic wastewater was investigated under hydraulic retention time (HRT) shocks to assess the effects on the microbial (bacteria and archaea) community and reactor performance. 16S rDNA targeted polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) approach was optimized to relate the metabolic and community composition with biogas generation, methane content and COD removal efficiency. From the drastic decrease of HRT (from 8 h to 4 h), the methane production was significantly reduced due to the HRT shock, while the COD removal efficiency was not affected. The enhanced growth of homoacetogenic bacteria, Thermoanaerobacteraceae competes with methanogens under shock period. When the HRT was recovered to 8 h, the methane generation rate was higher than the initial operation before the shock HRT changes, which would be ascribed to the activity of new emerging hydrogenotrophic archaea, Methanocella sp. and Methanofollis sp.