Perspectives of decentralised gasification of residual municipal solid waste

In the European Union (EU), the dominant technology for high-temperature thermal treatment of residual Municipal Solid Waste (i.e., the unsorted waste where source separation is performed) is the moving grate incineration. The process of combustion in this sector has been optimised thanks to the introduction of stringent criteria of operation both in the combustion chamber and in the treatment of the generated off-gas. However, the costs of treatment can be sustainable only if the tariff to be applied for the service is coherent with the average value found in the sector. The literature demonstrates that, under a capacity threshold, the grate system is out of market, thus limiting the implementation of small decentralised plants. This paper discusses the potential benefits of small-scale and decentralised thermo-chemical treatment plants replacing a single large-scale one. In addition, the present article analyses the consequences of the results of a recent survey that zoomed in on the availability of small-scale gasifiers for implementing such a strategy. The results of this analysis show that small-scale gasification is preferable to other technologies (e.g., incineration and pyrolysis) in terms of scale effect and flexibility/modularity. Compared to other thermal treatments, the local environmental impact could be reduced by converting syngas into fuels or chemicals rather than burning it for direct energy recovery. The paper also shows that small-scale gasification is able to respond to different needs in both EU and non-EU countries, like the management of progressively lower amounts of residual waste requiring treatment/management of uncontrolled dump sites.