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Abstract With drastic fossil fuel depletion and environmental deterioration concerns, a move towards a more sustainable bioenergy-based economy is essential. Lately, the application of microwave (MW) irradiation for waste processing has been attracting interest globally. MW-assisted heating possesses several advantages such as the provision of high microwave energy into dielectric materials with deeper penetration for internal heat generation, showing beneficial features in improving the heating rate and reducing the reaction time. Consequently, the most recent literature regarding the applications of MW-assisted heating for biomass pretreatment as well as biofuel and bioenergy production was reviewed and consolidated in this study. An impressive increase in the product yield and improvement of the product properties are reported, with the use of MW-assisted heating in several conversion routes to produce biofuels. Despite being a promising technology for biofuel production, some major fundamental data of MW-assisted heating have not been comprehensively identified. Therefore, the feasibility of this technology for large-scale implementation is still subpar. Understanding the interaction between the feedstock and the microwave electromagnetic field, and the optimization of several operational and mechanical parameters are the two main keystones that would propel the industrialization of MW heating in the near future. This provides key insights leading to increased feasibility and more advanced application of MW heating.

AbstractMountain treelines are thought to be sensitive to climate change. However, how climate impacts mountain treelines is not yet fully understood as treelines may also be affected by other human activities. Here, we focus on “closed‐loop” mountain treelines (CLMT) that completely encircle a mountain and are less likely to have been influenced by human land‐use change. We detect a total length of ~916,425 km of CLMT across 243 mountain ranges globally and reveal a bimodal latitudinal distribution of treeline elevations with higher treeline elevations occurring at greater distances from the coast. Spatially, we find that temperature is the main climatic driver of treeline elevation in boreal and tropical regions, whereas precipitation drives CLMT position in temperate zones. Temporally, we show that 70% of CLMT have moved upward, with a mean shift rate of 1.2 m/year over the first decade of the 21st century. CLMT are shifting fastest in the tropics (mean of 3.1 m/year), but with greater variability. Our work provides a new mountain treeline database that isolates climate impacts from other anthropogenic pressures, and has important implications for biodiversity, natural resources, and ecosystem adaptation in a changing climate.

We use extreme regional pollution emergencies to provide new evidence regarding the motivations for corporate social responsibility (CSR). We document that local firms strategically improve CSR to build trust following pollution emergencies, and this is specifically true for highly polluting firms. Firms face different intensities of external pressure from their stakeholders. In particular, following pollution emergencies, political dependency, institutional investors and public monitoring are the main sources of stakeholder pressure and drivers of the increased CSR. We further find that firms that gain trust through CSR activities after pollution emergencies are rewarded. CSR serves as a buffer against financial constraints, financing distress and the negative profitability effect following emergencies. This study contributes to the CSR literature on trust-building-motivated CSR strategies.

In the 21st century, many countries are starting to use geothermal energy (GTE) as a new energy source. Serbia also has the potential to use it as a renewable energy source. The complex geological structure of its terrain has given rise to a large number of thermomineral springs and geothermal wells. Based on the existing measurements, the geothermal heat flow density in Serbia ranges from 80 to 120 mW/m2, which is above Europe's average (60 mW/m2). Currently, there are 66 projects in Serbia that directly use geothermal energy. There are an estimated 1005 geothermal heat pump units. Their power varies between 10 kW and 40 kW and they operate for 2860 full load hours per year. This paper deals with the development, current state and perspectives of geothermal energy utilization for heating in Serbia. To illustrate the current state of geothermal energy utilization in Serbia, spa settlements Vranjska Banja and Gornja Trepča, as well as the Bogatić Municipality have been singled out as examples of good practice. The presented analysis includes determining the available amount of geothermal energy and its utilization for district heating or heating of selected public facilities. The concept and methodology of the presented research are based on data collection through literature review, surveys and field research. The analysis confirms the cost-effectiveness of using geothermal energy and reveals numerous ecological advantages over other energy sources. However, it was concluded that аlthough there is potential, geothermal sources, as a renewable energy source, are used negligibly in Serbia.