Recycling of fiber-reinforced thermoset composites using chemical solvolysis has been investigated thoroughly in recent years, where solvents such as water, alcohols and ketones have been used. However, high costs are related to the use of organic solvents, decreasing the sustainability of the process. In this study, acetone has been used as the organic solvent. To increase the sustainability of the process, the solvent was recycled in eight consecutive batches using new glass fiber-reinforced composites in each recycling. No additional amount of acetone was added, resulting in a reduction of solvent consumption by 88%. It was found that the recycled solvent became increasingly more concentrated with degradation products from the epoxy resin and compounds produced by acetone aldol reactions. These degradation products promoted and enhanced the degradation of the composite. Among the compounds produced by acetone aldol reaction, the industrially important bulk chemical mesityl oxide accounted for 68–79% of the total chromatographic peak area. Simultaneously, with the optimization of a process for converting composite waste into its constituent (fibers and resin), valuable bulk chemicals can be produced to increase the overall commercial interest.