Shipwrecks and Bathtubs Return to Cement: The History of FRP Waste Recycling, 2000s–2026

FRP, or fiber-reinforced plastic, is a composite material in which plastic resin is reinforced with glass fibers or similar materials. Because it is lightweight yet highly durable and resistant to corrosion, it has been used in a wide range of fields, including bathtubs, septic tanks, ships, construction materials, tanks, and automotive parts. However, the durability that is an advantage during use becomes a major challenge when the material is discarded. Unlike metal, it cannot be easily melted down for reuse, and because the resin and glass fibers are strongly bonded, separating the individual components is also difficult. For this reason, in the past, disposal often relied on landfilling or simple incineration. Against this backdrop, in the 2000s, attention turned to a recycling system in which FRP waste is shredded and used as raw material or fuel at cement plants. When FRP is finely crushed, the resin component can be used as a fuel that releases thermal energy, while the inorganic components, such as glass fibers, can potentially be utilized as raw materials for cement. In other words, the key feature of this approach is that it uses the waste material as both fuel and raw material, rather than simply burning it and leaving behind ash. Large FRP products, such as scrap ships and large bathtubs, presented particular challenges. Since these items are difficult to transport and feed into processing facilities as-is, they require pretreatment such as dismantling, cutting, and crushing. Because dust is generated during the crushing process, consideration for the work environment and equipment safety is also required. Furthermore, if transportation costs from collection sites to processing facilities become too high, the profitability of recycling itself decreases. Therefore, it is crucial to establish a comprehensive system that goes beyond just technology to include coordination with collection networks, logistics, and processing facilities. FRP recycling also serves as a pioneering example of how to integrate composite materials into a circular economy. A material created to last a long time is returned to society as a new resource after use. Rather than allowing its durability—which made it difficult to dispose of—to remain a drawback, the effort to convert it into alternative values, such as cement raw materials or fuel, symbolizes the transition from a society of mass production and mass disposal to a resource-recycling society.