or solvolysis. Mechanical recycling involves shredding the composites and using them as filler for other lower grade applications, yet this is limited to glass fiber composites like fiberglass. The fluidized bed process burns the composite materials and uses the heat to generate electricity. The matrix of the composite is also burned away leaving only the clean fibers that can be extracted out of the system. This recycling process has the ability to separate metals from carbon fiber while also coping with mixed composite materials; however, the process requires large amounts of hot air, and it leads to a slight change in fiber properties. Pyrolysis takes the carbon and heats the composites without oxygen present to detach the matrix and leaves only the fiber material; the process produces carbon dioxide or methane. Pyrolysis can also be used to create fuel from the composites which can be burned to produce energy. Solvolysis utilizes a solvent to break down the chemical bonds of the matrix, leaving behind the carbon fiber or other fiber material. Recycled composites have a more limited use as they cannot be used in critical components due to the difficulty in re-weaving recycled fibers and the decrease in fiber length that typically occurs during recycling. Parts that can not be directly recycled can be reused or upcycled into artwork, clothing, or furniture. For example, the company SkyArt takes composite and mixed plastics, which would typically end up in a landfill, and recycles them into aircraft simulators and other furniture. Environment Recycling parts from airplanes requires less energy than producing primary parts because manufacturing processes for materials such as aluminum and steel are energy intensive. Recycling in turn leads to a decrease in global greenhouse gas emissions. For example, recycling aluminum requires 95% less energy than producing virgin aluminum (non-recycled). However, when composites are recycled, the process must be done with the proper care to avoid environmental and safety issues. Certain composites can be classified as hazardous waste depending on the chemicals that coat them such as hexavalent chromium so extra precautions must be made when recycling these materials. Additionally, if a composite is carbon fiber, precautions must be taken when melting the material for recycling to avoid the release of electrically conductive fibers that can cause electrical interference in devices. Limitations Limitations in recycling aircraft materials include cost, impurities in alloys, hazardous materials, and quality of recycled components. The aircraft