The construction industry’s high demand for natural resources, combined with the waste generated by agriculture, creates an opportunity for the circular economy. This experiment used the CaCO3 found in scallop shells as an ingredient for the manufacture of fire-resistant materials, replacing gypsum in compositions of 40% and 50% by weight. The mechanical compressive strength was estimated for both freeze-thaw cycles and acid and sulfate attacks. The cost of disposing of scallop shell waste in landfills, savings from substitution, and the payback period relative to the amount of production were determined. The compressive strength of the materials decreased by 80% when subjected to freeze-thaw cycles and sulfate attack. In response to acid attack, they showed a 100% increase in strength during the first three weeks and a decrease thereafter. The savings amounted to $46.36 (22.4%) for 40% replacement and $58.93 (28.4%) for 50%. Respectively, return on investment is achieved at 800- and 630-per-metric ton produced. The difference between the costs of waste disposal (in aquaculture) and the potential savings from using CaCO3 as a raw material (in construction) creates an opportunity for commercialization between the two industries, serves as a reference for decision-makers, and complies with circular economy principles, reducing both inputs of raw materials and outputs of waste.