**6. Energy Transition in the Mekong Subregion**

The Mekong Subregion faces mounting challenges in matching its energy demand with sustainable energy supply. This is because the regional reliance on fossil fuel consumption is projected to last at least until 2050. The transition to a lower-carbon economy will require the region to develop and deploy greener energy sources and clean use of fossil fuels through innovative technology such as high-efficiency, low emissions (HELE technologies) technologies. Coal-use patterns in the region reflect the rising demand for electricity to power and steer economic growth. Hence, building low-efficiency CPPs is an obvious choice for power-hungry emerging Southeast Asia due to lower capital costs. However, such plants cause more environmental harm and health issues due to air pollution, CO2, and other GHG emissions. Widespread coal power plant construction could also point to the low environmental standards for coal-fired power generation in the Mekong Subregion [78]. The Mekong Subregion countries have relatively high allowable emissions in terms of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM) (see Figure 6). This means that countries in the subregion have lower emissions standards than advanced countries such as Germany, the Republic of Korea, and Japan, where HELE coal fired power plants are mandatory.

Major harmful air pollutants, such as SOx, NOx, and PM, come from fossil fuel and biomass power plants, which therefore need to be carefully regulated. It is known that short-term exposure to sulfur dioxide (SO2) can harm the human respiratory system and make breathing difficult.

Thus, the Mekong Subregion's leaders may need to consider more strongly the promotion of HELE technologies, higher standards or stringent environmental regulation for CPPs, and effective enforcement. This may push investors to select more advanced technologies, especially ultrasupercritical technology, for CPPs. Such plants are considered clean power because they use coal more efficiently and cleanly than traditional subcritical CPPs. Furthermore, supporting frameworks to ensure that developing countries can afford HELE technologies are urgent because the up-front investment costs of HELE technologies are much higher than those of traditional CPP technologies.

The role of natural gas in the energy transition cannot be overlooked. This is because it can be used as a bridging fuel between high emissions fuels, such as coal and oil, to cleaner energy systems in which renewables and clean fuels take the major share in the energy supply mix. The prospects for using natural gas in the Mekong Subregion are good, with demand likely to quadruple depending on the future stability of gas and liquefied natural gas (LNG) prices in the market; whether a competitive gas/LNG market can be created in Southeast Asia; and the role of gas/LNG from Australia, the US, and other sources. The region is expected to be a key market for future gas demand, thus gas infrastructure

investment, such as gas pipelines and LNG terminals, will be crucial in supporting the demand for gas in the region [79].

**Figure 6.** Emissions standards for newly constructed CPPs in selected countries (SOx, NOx, and PM). CPP = coal-fired power plant, mg/m<sup>3</sup> = milligram per cubic meter, SOx = sulfur oxides, NOx = nitrogen oxides, PM = particulate matter. Source: Mitsuru et al. [78].

In the current situation, hydropower accounts for quite a large share of the energy mix in the Mekong Subregion. However, as energy demand is expected to increase further, hydropower sources will be fully utilized. Thus, the share of renewables, such as wind, solar, and biomass, will play a critical role in the future clean energy system in the Mekong Subregion. The lower cost of these renewables will make it possible for a higher share of wind and solar in the energy mix [80]. Since electricity from wind and solar sources is variable and intermittent, there is a need to invest in grid infrastructure with smart grids, using the Internet of Things (IoT) and other technology to predict electricity production.

The Mekong Subregion may benefit enormously from the development of renewable hydrogen, as the region has large hydropower potential and the possibility of a higher share of solar and wind power see [77]. Thus, electricity from wind and solar plus other unused electricity during low-demand hours should be converted to hydrogen as stored energy. Fast-moving technological development will drive down the cost of hydrogen production in the future and give hydrogen a larger role in the clean energy future [81]. Thus, the Mekong Subregion may need to prepare a roadmap for rolling out a hydrogen plan in the future.
