Biodeterioration of asbestos cement using Lacticaseibacillus paracasei: A pre-treatment for sustainable waste...

Despite asbestos bans in many industrialized countries, asbestos cement (AC) waste remains widespread, mostly landfilled due to high neutralization costs. This study evaluates biochemical treatment to reduce asbestos cement mass through matrix dissolution. Experiments used AC monoliths exposed to lactic acid-producing Lacticaseibacillus paracasei ssp. paracasei cultures at 30°C, with a solid-liquid ratio of 10 g/L. Over 7 days of biodegradation, bacterial metabolism maintained acidic conditions, counteracting the pH increase from dissolving alkaline phases such as calcite and C3S, resulting in 17-25 % mass loss. X-ray diffraction analysis confirmed selective dissolution of the cementitious matrix while preserving asbestos fibers. Geochemical modeling with PHREEQC revealed an initial pH spike due to surface neutralization, followed by steady dissolution kinetics without surface passivation. However, increasing reactive surface area excessively, such as by grinding, leads to rapid pH rises that trigger calcite re-precipitation, reducing process efficiency; thus, grinding is discouraged. While this approach shows promise as a pre-treatment to reduce asbestos-cement waste volume prior to final inertization, limitations include pH control and challenges associated with scale-up. Overall, this biodeterioration process provides a laboratory-scale proof of concept that could inform the future development of sustainable and cost-effective strategies for asbestos waste management.