Coal-fired power plants in Vietnam generate more than 25 million tonnes of ash and slag annually, a volume that for years strained landfills and raised environmental risks. What has shifted the debate is not a reduction in coal use but a sharp increase in reuse.
Official data show that ash and slag utilization rose from 37.5 percent in 2018 to 84 percent in 2021, before reaching full absorption across much of the sector from 2022 onward, effectively turning a persistent waste stream into an industrial input.
Vietnam currently operates 31 coal-fired thermal power plants, all of which have approved plans for ash and slag treatment and consumption under national regulations. According to the Ministry of Industry and Trade, conformity certification has largely been completed, allowing these byproducts to meet technical standards for use in cement additives, concrete admixtures, construction materials, and backfilling. This regulatory alignment has been a prerequisite for market uptake, particularly in construction applications that demand consistent material quality.
Electricity of Vietnam and its subsidiaries report that consumption rates climbed from 33 percent in 2015 to 100 percent since 2022 when including the drawdown of legacy stockpiles. The pace of utilization now exceeds generation in some periods. In the first eight months of 2025, thermal power plants produced 4.57 million tonnes of ash and slag but consumed 5.31 million tonnes, equivalent to 116 percent of output. This surplus reflects the accelerated processing of material accumulated over previous years, particularly at plants in Hai Phong, Pha Lai, Ninh Binh, Thai Binh, and Uong Bi.
The Ministry of Construction estimates that cumulative nationwide consumption of thermal power ash and slag has surpassed 100 million tonnes. Around 55 percent of this volume has been used for backfilling, making it the single largest application by tonnage. Cement and concrete production accounts for much of the remainder, where fly ash is valued for improving fineness, compressive strength, and water resistance while reducing clinker demand. Associate Professor Luong Duc Long, former director of the Institute for Building Materials, notes that when quality is properly controlled, coal ash can substitute for natural materials such as sand and stone without compromising performance.
From an industrial perspective, demand has remained stable. Enterprises using ash and slag report multi-year contracts and predictable offtake, suggesting that recycled coal byproducts have moved beyond pilot use into routine supply chains. This has direct environmental implications. Each tonne of ash diverted from landfill reduces land use pressure and mitigates dust and leachate risks, while material substitution lowers the extraction of virgin aggregates.
Operational practices have also evolved. At the Duyen Hai Thermal Power Plants, ash and slag handling includes zoned disposal areas, compaction, impermeable liners, vegetation cover, and dust suppression to ensure environmental safety prior to recovery. The operator reports a current utilization rate of about 99 percent across its three units. To reach a consistent 100 percent by 2026, the company is working with the Institute for Construction Science and Technology to maintain testing and certification for fly ash used in concrete, mortar, and cement, while expanding partnerships for backfilling applications.
Despite the progress, constraints remain. Supply fluctuates with seasonal power generation, complicating logistics for downstream users. Technical guidance for certain uses such as roadbeds, land reclamation, and large-scale coastal projects is still incomplete, slowing approvals. Transport distance is another structural barrier, as moving low-value bulk materials over long ranges erodes economic viability. Investor caution persists even when products meet national standards, reflecting lingering concerns about consistency and regulatory clarity.
Industry experts argue that the next phase depends less on technology and more on policy refinement. A more comprehensive system of standards and technical regulations could reduce uncertainty and unlock larger infrastructure uses, including ports and industrial zones. Enterprises have also called for mechanisms to offset transport costs, particularly where power plants are distant from construction demand centers.
