Exploring Potential Materials, Science, and Technology for Improvements in Reusing Energy and Waste

Exploring the science and engineering of new approaches to energy and waste reuse is both a very important and very interesting issue. There have been great efforts made to find potential materials, science, and technology for improvements in the reuse of energy and waste, to ensure energy sustainability and to increase the effectiveness and efficiency of engineering processes to achieve optimum energy production. Most of the efforts have been devoted to materials for photovoltaics, hydrogen production, batteries, and green energy. The range of materials of interest is very wide, from polymers to quantum dots. However, the engineering and environmental issues still present limitations, such as high energy demands, catalyst costs, and insufficient reuse or regeneration of spent adsorbents and catalysts. These challenges have opened new exploration of, for example, cheaper precursors, regeneration of spent adsorbents or catalysts, extraction of useful elements from waste, and overall optimization of engineering processes. More recently, multifunctional and advanced materials have started to show promise for future applications. Integration of economical precursors, high performance materials, efficient methods, easy-to-use designs, and cost-effective manufacturing are always required for competitive energy production, and one would therefore expect clean energy that could address global warming to remain a major issue for many years. Development of alternative uses and reuses of by-products (waste) has also been of interest, not only to reduce the production of carbon dioxide, but also to achieve zero-waste policies. Overall, efforts are being made toward achieving high efficiency, economical or low-cost, renewable, and eco-friendly energy production. Adsorption processes utilizing agro-waste as a simple method for removing heavy metals, pollutants, and odor from wastewater, are another important thread for environmental and industrial applications. Exploring new alternative adsorption processes and low-cost, highly efficient, and abundant adsorbents from agro-waste are being pursued for the further development of environmental applications that could remove or reduce a diverse range of hazardous pollutants and facilitate minimization methods for the management of waste on large a scale. To address the above issues, the 3rd International Tropical Renewable Energy Conference (i?TREC) 2018, with the main theme of “Sustainable Development of Tropical Renewable Energy,” was held on September 6–8, 2018, at the Discovery Kartika Plaza, Bali, Indonesia. This conference was   proudly organized by the Tropical Renewable Energy Center, Faculty of Engineering, Universitas Indonesia. The conference consisted of four symposia, including Smart Grids and Regulation, Bioenergy, Multifunctional and Advanced Materials, and Eco Tropical Built Environment. The current edition consists of 21 peer-reviewed papers, out of 313 papers submitted to the 3rd International Tropical Renewable Energy Conference (i?TREC) 2018, which are divided based on the symposia topics. The 21 presented and selected papers come from various countries, including the USA, UK, Canada, Brunei Darussalam, Malaysia, and Indonesia. At the conference, the participants updated the current trends in new materials and approaches to reuse of energy and waste, providing a space for discussion focusing on the methodology, technology, and empirical work of tropical renewable energy. Publishing information on the conference via traditional printed media, however, takes time and, for several reasons, the discussion presented therein might remain unknown to a wider audience.   In this special issue of the International Journal of Technology, we would therefore like to present the discussions in the form of research papers, and thereby make it available to a wider readership and, with the inclusion of these published materials, enrich and extend the i-TREC conference reports