Microwave-Assisted Pyrolysis of Solid Waste

In this paper, results of further work on pyrolysis processing of mixed solid wastes for spacecraft applications are reported. A domestic microwave oven was modified for scoping studies in which the effects of sample size and the use of distributed versus central microwave absorbers were studied. Experiments were done with wheat straw and included those in which the sample was rotated during pyrolysis in order to improve heating uniformity. The experiments using central microwave absorbers of various compositions included a ferrite rod, a quartz tube filled with activated carbon, and silicon carbide. The ability to monitor the sample temperature and sample heating uniformity during microwave heating was demonstrated. A comparison was made with conventional pyrolysis experiments in an electrically heated furnace to a similar final temperature. In general, it was found that microwave heating reduced the energy demand by about 50% and increased the yield of gas products by about 100%, while reducing the char yield about 20%.