This type of combustion (a simple modification to mass burn) involves the waste to be used as fuel being suspended by an updraft supply of air and kept 'fluidised' on a base of small inert particles such as sand. The waste is effectively mixed with the hot bed material to ensure it is fully burned. Fluidised bed combustors come in many different designs, for example circulating and bubbling beds (indeed there are also designs for application to gasification and pyrolysis technologies). They all require the waste to be of uniform size which signifies that a pre-treatment shredding stage is required which adds to the cost of the process. Conversely, savings are made as compared to basic incineration systems that spring from the possibility of including lime in the combustor material to inhibit the production of acid pollutants. Consequently, there is no need for the expensive bolt-on air pollution control system typical to mass burn incinerators which remove them once in the flue gases. These factors balance out so the cost per tonne of processing is not markedly different between the two processes. However, fluidised bed systems are typically smaller so they may befit a community smaller than is needed to maintain a mass burn system.

The shredding process can be interwoven with materials recycling, however while ferrous metals can be easily separated, much of the rest of the material will be lost and a large proportion will not be suitable for recycling, for example paper which needs to be kept clean.