## 1 Introduction
### Waste to Energy in Asia
Thus, construction costs vary widely, and a typical range in Europe is around 500-700 Euro per ton per year in installed capacity, not including the cost for the site and project development [21]. Globally, the estimated cost for the waste-to-energy technologies in the lower middle income countries is in the range of 40-100 US dollar (USD) per ton for incineration and 20-80 USD per ton for anaerobic digestion (AD), while the estimated cost in high income countries is in the range of 70-200 USD per ton for incineration and 65-150 USD per ton for AD [1]. Figure 5 illustrates that the application of waste-to-energy technologies in low-income and lower middle-income countries is merely at the development stage compared to the upper middle-income and high-income countries, which are actively using these technologies. In Figure 6a, the forecast shows that, globally, the growth of waste-to-energy technologies is projected to reach 24.5 million USD in 2024 from 2.1 million USD in 2010. Meanwhile, the regional market investment in incineration in Asia will have grown from 616 million USD in 2006 to 6463 million USD in 2021, representing an investment increase by a factor of 10 (Figure 6b). Additionally, the Asia-Pacific waste-to-energy market is projected to grow at an annual rate of over 15% and will reach a value of 13.66 billion USD by 2023 [22]. Thus, it is seen that the waste-to-energy sector in Asia has a great potential in technological transfer and investment [15; 23]. Figure 5: Waste disposal method by income [1]. Currently, waste incineration is uncommon in developing countries, and, generally, it is not successful or experiences financial and operational difficulties due to the high capital cost of the plant, operation and maintenance costs, the high moisture content of MSW, and the need for sorting facilities and pretreatment processes [1; 18]. However, energy-oriented conversion technologies for waste-to-fuel and waste-to-energy have been well-developed around the world to create energy/fuel from waste, reduce dependency on fossil fuel, reduce land use for waste disposal, and ensure socio-economic and environmental benefits [24; 25; 26]. Though there is still a long way until a global sustainable waste management strategy is achieved [15], developing countries can learn the lessons about and gain technology transfers from the waste-to-energy technologies and waste management practices in developed countries. Nowadays, most Southeast Asian countries are facing several issues related to waste management, such as the increasing annual waste generation that has required more waste disposal sites, the scarcity of land areas, environmental pollution, and growth in energy demand [4; 5; 7; 27]. Since these issues are especially important to be tackled in Southeast Asia, waste-to-energy technologies can play an essential role in sustainable waste management and the relief of environmental matters [17; 25; 26]. Meanwhile, some aspects such as regulation, finance, and technological suitability should be carefully considered to develop the waste-to-energy sector in the region [2; 12; 15; 16; 18; 24]. Several studies have, to a reasonable extent, overviewed, analyzed, and evaluated the waste management and waste-to-energy sectors in Southeast Asian countries [1; 28], but most have focused on the waste-to-energy sector in specific countries such as Thailand [29; 30], Malaysia [31; 32; 33], Vietnam [17], and Myanmar [13]. Despite some issues such as public perception, public-private partnerships, all stakeholder involvement, funding, and climate factors, some Southeast Asian countries have made a reasonably successful step toward waste-to-energy technologies. Therefore, this study aimed to highlight an overview of the waste-to-energy sector in Southeast Asian countries to specify the status, challenges, opportunities, and selection of technologies suited for a specific country.