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Purpose This study aims to consider environmental sustainability, a global challenge under the preview of sustainable development goals, highlighting the significance of knowledge economy in attaining sustainable aggregate demand behavior globally. For this purpose, 155 countries that have data available from 1995 to 2021 were selected. The purpose of selecting these countries is to test the global responsibility of the knowledge economy to attain environmental sustainability. Design/methodology/approach Results are estimated with the help of panel quantile regression. The empirical existence of aggregate demand-based environmental Kuznets curve (EKC) was tested using non-linear tests. Moreover, principal component analysis has been incorporated to construct the knowledge economy index. Findings U-shaped aggregate demand-based EKC at global level is validated. However, environmental deterioration increases with an additional escalation after US$497.945m in aggregate demand. As a determinant, the knowledge economy is reducing CO2 emissions. The knowledge economy has played a significant role in global responsibility, shifting the EKC downward and extending the CO2 reduction phase for every selected country. Further, urbanization, energy intensity, financial development and trade openness significantly deteriorate the environmental quality. Originality/value This study contains the empirical existence of aggregate demand-based EKC. The role of the knowledge economy is examined through an index which is calculated by using four pillars of the knowledge economy (technology, innovations, education and institutions). This study is based on a combined panel of all the countries for which the data was available.

As an effective emission reduction approach, CO2 capture and storage (CCS) combined with enhanced water recovery (EWR) technology can not only reduce CO2 emissions, but can also recover deep saline water resources to relieve pressure on regional water resources, and can ensure the energy supply and both social and economic development. However, the environmental benefits and application costs of CCS-EWR are uncertain, and are determined by the technology level, geological conditions, and other physical factors. In this study, an optimal source-sink matching model and a techno-economic assessment model were developed to evaluate the contributions of CCS-EWR to carbon emission reduction and the increase of the water supply by considering various uncertain factors, as well as the corresponding costs. In addition, the Yellow River Basin (YRB) in China was selected as the research region because, while there are abundant coal-fired power plants (CFPPs) in the YRB, the water resources are scarce. The results revealed the following. (1) The maximum CO2 capture capacity of the 236 CFPPs in the YRB is about 738.77 Mt/a, and nearly 13.14 Gt of fresh water could be provided until the 236 CFPPs in the YRB retire, which can partially relieve the pressure on the supply of water resources. (2) With the consideration of the CCS-EWR benefits, the average cost of the 236 CFPPs in the YRB in their residual lifetime to reduce their CO2 emissions by 90% will be no more than 180 CNY/t. (3) The incentive effect of the increase of the industrial water price on the profits of CCS-EWR projects is not significant. CCS-EWR technology has better application prospects in China under the dual constraints of carbon-neutral targets and water shortages, and more policy support is required for its deployment.

A key factor in social development and sustainable urban expansion is the establishment of sustainable and affordable transport systems. This study aims to investigate the impact of transport infrastructure investment on environmental degradation and economic growth and to test the validity of the EKC hypothesis in China, India, Russia, and Japan over the period 1995-2020. The results show that GDP has a significant positive effect, and GDP2 and GDP3 have significant adverse effects on environmental degradation, respectively. These results confirm the validity of the inverted U-shaped EKC hypothesis in selected emerging Asian economies. Rail infrastructure investment has significant adverse effects, while road infrastructure investment and aviation infrastructure investment have significant positive effects on environmental degradation. Likewise, the impact of investment in transport infrastructure system (roads, rail, and aviation) on economic growth is positive and statistically significant. Country-level estimates confirm the validity of the inverted U-shaped EKC hypothesis in China, India, and Russia, while the N-shaped EKC is only valid in Japan. Investments in rail infrastructure based on modern rail systems that run on electricity are believed to be less polluting in the transport mix, help create sustainable and safe transport systems, and reduce emissions at the urban and intercity levels in emerging Asian countries. In addition, the growing impact of free trade on environmental pollution should be strengthened to harmonize the strict enforcement of environmental conditions dominated by trade agreements.

Environmental quality indicators are crucial for responsive and cost-effective policies. The objective of the study is to examine the relationship between environmental quality indicators and financial development in Malaysia. For this purpose, the number of environmental quality indicators has been used, i.e., air pollution measured by carbon dioxide emissions, population density per square kilometer of land area, agricultural production measured by cereal production and livestock production, and energy resources considered by energy use and fossil fuel energy consumption, which placed an impact on the financial development of the country. The study used four main financial indicators, i.e., broad money supply (M2), domestic credit provided by the financial sector (DCFS), domestic credit to the private sector (DCPC), and inflation (CPI), which each financial indicator separately estimated with the environmental quality indicators, over a period of 1975-2013. The study used the generalized method of moments (GMM) technique to minimize the simultaneity from the model. The results show that carbon dioxide emissions exert the positive correlation with the M2, DCFC, and DCPC, while there is a negative correlation with the CPI. However, these results have been evaporated from the GMM estimates, where carbon emissions have no significant relationship with any of the four financial indicators in Malaysia. The GMM results show that population density has a negative relationship with the all four financial indicators; however, in case of M2, this relationship is insignificant to explain their result. Cereal production has a positive relationship with the DCPC, while there is a negative relationship with the CPI. Livestock production exerts the positive relationship with the all four financial indicators; however, this relationship with the CPI has a more elastic relationship, while the remaining relationship is less elastic with the three financial indicators in a country. Energy resources comprise energy use and fossil fuel energy consumption, both have distinct results with the financial indicators, as energy demand have a positive and significant relationship with the DCFC, DCPC, and CPI, while fossil fuel energy consumption have a negative relationship with these three financial indicators. The results of the study are of value to both environmentalists and policy makers.

Abstract The transportation and electricity sectors are in the midst of leading changes in the endeavor to mitigate climate change and air pollution issues. In future years, traditional fossil-fuelled vehicles are estimated to be substituted with electric vehicles (EVs), resulting in higher electricity demand from the transport sector. Meanwhile, the electricity sector is transforming due to policies to adopt renewable energy resources such as solar, wind, and hydropower in the future. However, there are still societal concerns regarding the environmental benefits of these vehicle technologies and how new energy options and vehicles benefit the 2050 HK Carbon Neutral Plan. To address these concerns, this paper aims to analyse the environmental burdens of current (2019) and future (2050) vehicle scenarios in Hong Kong using a life cycle assessment (LCA). The LCA was performed for internal combustion vehicles (ICEVs) fuelled by diesel and petrol and plug-in hybrid vehicles (PHEVs) and EVs with future electricity energy mix scenarios (2025–2050). The results revealed that EVs with the 2050 HK electricity mix are an optimal choice and have the least environmental impact in selected impact categories. Additionally, PHEV with diesel were the second most optimal choice to reduce the environmental impacts in current scenarios. In contrast, the petrol ICEV has the utmost environmental impacts in all damage category results. The study shows that clean energy could decrease the environmental impact and mitigate climate change in Hong Kong.

Abstract Energy shortage in developing countries is one of the major challenges for sustainable development. Such challenges can be met and managed via indigenous, clean and reliable alternate energy sources like biogas and bioenergy especially at household levels. The household biogas technologies are now flourishing and conveniently accessible through certain Government and NGO funded schemes. In the current study household scale floating drums and fixed dome type biogas plants and their economic aspects were reviewed along-with technological and operational assessments. The results shown that 1 kW of energy can be generated from 0.65 m 3 of biogas by such household biogas units, furthermore it was evident that fixed dome type biogas plants were more economical with shortest payback period of about four months. Additionally effluent slurry being generated by such biogas plant can be a profitable provision in-terms of bio-fertilizer for agricultural. Overall the study results deliberated an optimistic picture for a developing country like Pakistan on the basis of installation of such small household biogas plants and utilizing indigenous technologies and feedstock. The net annual savings calculated were as US$ 837.67, US$ 829.03 and US$ 845.25 for steel floating drum type, fiberglass composite (FRP) floating drum type and fixed dome type household biogas plants, respectively.

Non-renewable energy sources have remained the choice of the world for centuries. Rapid growth in population and industrialisation have caused their shortage and environmental degradation by using them. Thus, at the present rate of consumption, they will not last very long. In this prospective, this study has been conducted. The estimation of energy in terms of biogas and heat from various organic fractions of municipal solid waste is presented and discussed. The results show that organic fractions of municipal solid waste possess methane potential in the range of 3%–22% and their heat capacity ranges from 3007 to 20,099 kJ kg−1. Also, theoretical biogas potential of different individual fruit as well as vegetable components and mixed food waste are analysed and estimated in the range of 608–1244 m3 t−1. Further, the share of bioenergy from municipal solid waste in the total primary energy supply in Pakistan has been estimated to be 1.82%. About 8.43% of present energy demand of the country could be met from municipal solid waste. The study leads us to the conclusion that the share of imported energy (i.e. 0.1% of total energy supply) and reduction in the amount of energy from fossil fuels can be achieved by adopting a waste-to-energy system in the country.

Abstract Biodiesel is typically produced from a wide variety of edible vegetable oils. The cost of biofuels is projected to rise in the future as an alternative and ecologically suitable replacement to traditional fuel. Reliable and inexpensive raw materials, including meat processing by-products or waste animal fats, have rapidly attracted interest in biodiesel production. The operational and reaction parameters play an important role in the conversion of processes and biodiesel yield. Kinetic models explain the reaction rate and process optimization to improve the biodiesel conversion process. The process intensification approaches applied by different researchers are illustrated in the current study. This paper proposes a groundbreaking solution to stepping up biodiesel development by utilizing a coalescer reactor and a preliminary review to justify the solution's potential for further analysis. Optimization techniques and kinetics studies used to enhance biodiesel production from renewable sources are explored in the current review paper.

Abstract Energy indices provide a clear summary to measure the energy performance of the country which is a prerequisite for policy making. Increasing rate of greenhouse gases (GHGs) emissions are causing dangerous climate changes which seem irreversible. Therefore, it is vital to rank countries with the highest GHGs and carbon emissions in order to develop low carbon economies. This requires a comprehensive statistical analysis. In this study, we develop an aggregated composite index (ACI) of energy security and environmental sustainability for each of the world’s highest GHGs and CO2 emitting countries. Our index is based on a comprehensive set of indicators including carbon emission and energy metrics. Composite indicator has been used to combine all the indicators in a holistic way. Higher values show a better efficiency and vice versa. The analysis reveals that there are considerable differences in performances of top and low ranked countries, Canada and Brazil respectively. We ranked the countries based on their efficiency score from top-down. Analysis also provides a roadmap and guidelines for the future policymakers.