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 very durability that is an advantage during use becomes a major challenge when the material is discarded. Unlike metal, it cannot be easily melted down and reused, and because the resin and glass fibers are strongly bonded, separating the different components is also difficult. For this reason, landfilling and simple incineration were often the primary disposal methods in the past. 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, have the potential to be utilized as raw materials for cement. In other words, the key feature of this approach is that it utilizes the waste material as both fuel and raw material, rather than simply burning it and leaving behind ash. Large FRP products, such as scrapped ships and large bathtubs, posed 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 includes not only the technology but also 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, efforts to convert it into alternative values, such as cement raw materials or fuel, symbolize the transition from a society of mass production and mass disposal to a resource-recycling society.