Co-pyrolysis re-use of sludge and biomass waste: Development, kinetics, synergistic mechanism and industrialization

The production and accumulation of sludge, as well as other biomass wastes, places a long-term burden on the urban ecosystem. Pyrolysis is an advanced waste disposal technology that can achieve harmless treatment and meanwhile produce clean energy (biogas, biochar, and bio-oil) to replace traditional fossil fuel. Co-pyrolysis, in particular, has potential to improve traditional pyrolysis in terms of pyrolysis efficiency and product quality, and thus is regarded as a new generation of environmentally friendly energy production techniques. Existing reviews on co-pyrolysis for sludge with other biomass wastes are scarce, and their complex co-pyrolysis mechanisms require systematic review so as to guide future technological progress. This work delivers an assessment of co-pyrolysis of sludge with various biomass wastes. Various kinetic methods and data show that the multi-step distributed activation energy method is the most suitable for co-pyrolysis studies. The synergistic promotion mechanism is crucial to increasing product application pathways so that all co-pyrolysis products (biogas, biochar, and bio-oil) may be delivered as revenue, making this technology much more economically viable. Furthermore, it also discusses prospects and challenges for successful industrialization of sludge co-pyrolysis.