The construction industry is currently facing significant pressure to reduce its environmental impact, particularly regarding the carbon intensive production of Portland cement. A recent study published in Scientific Reports by authors Stephen Babajide Olabimtan, Mohammad Ali Mosaberpanah, and Babatunde Olufunso Oluwole explores a circular economy solution by utilizing marine biomass waste. The researchers investigated the performance of mortar containing biochar derived from the leaves of Posidonia oceanica, a seagrass endemic to the Mediterranean Sea. By transforming these waste leaves into a carbon rich material through pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More and using it to partially replace cement, the study addresses the dual challenge of marine waste management and the need for more sustainable building materials.

The findings reveal that the addition of this marine biochar significantly influences the mechanical and durability properties of mortar in a dosage dependent manner. While adding biochar generally reduces the workability of the fresh mixture because of its porous nature and high water absorption, the hardened properties show remarkable improvements at specific concentrations. The research identifies three percent as the optimal replacement level for achieving the best balance of performance and sustainability. At this level, the mortar exhibited an 8.71 percent increase in compressive strength after twenty eight days compared to traditional mixtures. This improvement is primarily credited to the fine particles of the biochar acting as a filler that densifies the internal structure of the material, making it more compact and robust.

Durability testing further highlighted the benefits of including marine biochar at the optimal three percent dosage. The study found that these modified mortars were more resistant to water penetration, which is a critical factor for the longevity of structures. Furthermore, the biochar modified specimens showed superior performance when exposed to harsh chemical environments. After immersion in sulfuric acid for twenty eight days, the three percent biochar mortar retained more of its original strength and experienced less mass loss than the control specimens. The biochar acts as a stable barrier within the cement matrix, shielding the more vulnerable components of the concrete from acidic degradation.

One of the most impressive results of the study concerns the material’s resilience to extreme heat. When subjected to temperatures as high as 600 degrees Celsius, the mortar containing three percent biochar remained structurally intact and maintained its compressive strength. In contrast, traditional mortar and those with higher biochar concentrations suffered from severe cracking and structural failure. The porous network within the biochar particles provides a vital escape route for water vapor generated during heating, which prevents the buildup of internal pressure that typically leads to explosive spalling in concrete structures during a fire.

From an environmental perspective, the use of Posidonia oceanica biochar offers a clear path toward greener construction. The researchers calculated that replacing six percent of cement with biochar can lead to a 5.3 percent reduction in embodied carbon. However, because higher dosages lead to a decline in mechanical strength, the three percent replacement level was determined to be the most efficient choice, offering a 2.53 percent carbon reduction while still enhancing the material’s strength. This study positions marine waste biochar as a viable and effective alternative to traditional cement, supporting the development of low carbon infrastructure while providing a productive use for abundant ocean biomass.

Source: Olabimtan, S. B., Mosaberpanah, M. A., & Oluwole, B. O. (2026). Mechanical and durability performance of mortar containing biochar derived from pyrolyzed Posidonia oceanica leaves: a circular approach to marine biomass waste. Scientific Reports.