Utilizing Biochar from Pyrolyzed Biosolids with Mycelium for Sustainable Concretes

The concrete industry is pivotal to modern infrastructure because of its scalability, low cost, and long-lasting performance. However, it is also a landmark contributor to climate change. With the growing interest in easy and mass producible climate-friendly solutions and alternatives to landfill disposal, materials like biochar from pyrolyzed municipal biosolids, when implemented in building materials, can provide a potential solution. Biochar can reduce organic waste and serve as a carbon-sequestering additive in concrete. Another material, mycelium (the root-like structure of mushrooms) is another example of a renewable alternative to traditional concrete ingredients to offset greenhouse gas emissions and reduce agricultural waste. Ratios of biochar ranging from 0.3 to 50% were implemented as a partial weight replacement for fine aggregates in concrete to increase compressive strength and carbon storage capacity. Pure concrete and mycelial bricks were developed as a control. The process was mirrored for mycelium: ratios of biochar ranging from 5–20% by weight partially replaced mycelium substrate to observe the impact of biochar on the strength and density of mycelial networks. A hydraulic press was utilized to test the compressive strength of concrete and mycelium specimens to determine the effectiveness of biochar. The fine aggregate replacement in concrete of 5% by weight biochar roughly doubled the compressive strength in specimens compared to conventional concrete. Biochar particles were photographed under a scanning electron microscope and compared to photographs of sand. The biochar ratios that produced the strongest concrete and mycelium samples were combined into a single hybrid material, with partial fine aggregate replacement of biochar and partial coarse aggregate replacement of mycelium, to manufacture an optimized, ecofriendly concrete alternative.