Study of seashell waste recycling in fireproofing material: Technical, environmental, and economic assessment

The productive sector must incorporate waste into traditional materials in order to grow sustainably. In Galicia (Spain) alone, the canning industry produces over 150,000 metric tons of seashell waste per year. Most of this waste is still disposed of in landfills or open fields due to the lack of a technically feasible, environmentally sustainable, and economically profitable recycling alternative. This paper aims to study the feasibility of a new recycling alternative for seashell waste from industrial canning, based on the production of fireproof material suitable for construction use. The waste was pre-treated in order to remove salts and remaining organic matter and reduce particle size. According to international standards, physical, mechanical, and insulating properties were assessed for four compositions: 0, 40, 60 and 80% of gypsum substituted with pre-treated seashell waste. Results showed that substitution of up 60% gypsum was technically feasible. A Life-Cycle Assessment and a preliminary production cost analysis were performed by analysing a recycling case in Galicia. The case study found that 40-60% gypsum substitution obtained an environmental impact reduction of 0.4%-59% for 13 of the 18 impact categories considered compared with 0% substitution. Increases in the other 5 categories were analysed due to aquatic emissions released in the waste pre-treatment washing process. The locations of the fireproof material production facility and the waste source were a key factor. Production costs could be reduced by 20-31% by using 40-60% gypsum substituted with seashell wastes.