Turning Waste into Greener Cementitious Building Material: Treatment Methods for Biomass Ashes—A Review

The production of biomass ash (BA) is expected to increase in the future, as biomass is generally considered a carbon-neutral fuel. BA potentially concentrates heavy metals and trace elements at high levels. With the growing production of BA, its disposal in landfills or recycling must be addressed through solid waste policies and within the framework of a circular economy. Utilizing BA as a cement substitute solves disposal issues while offering environmental benefits aligned with the circular economy. However, the varying physical and chemical properties of BA, influenced by factors such as biomass type and combustion technique, necessitate more effective utilization strategies. Consequently, researchers are developing various treatment methods to ensure that BA meet the necessary requirements and do not pose problems such as heavy metal or chlorine leaching. These treatments facilitate the production of concrete with higher compressive strength at greater cement replacement levels, supporting greener construction practices. This review consolidates existing BA data and treatment methods, focusing on their impacts and efficiency. It also explores combined treatments and potential new approaches. By providing a foundation for future research and practical applications, this study aims to improve treatment techniques, helping the industry mitigate environmental risks and advance carbon-neutral construction solutions.