Review on the Current Status of the Co-combustion Technology of Organic Solid Waste (OSW) and Coal in China

Increasing economy and population result in the rapid growth of solid waste in China, with more than 70% being carbonaceous components. The generated carbon-bearing solid waste is called as organic solid waste (OSW). In this Review, OSWs from both municipal and industrial sources are discussed and divided into municipal solid waste (MSW), organic sludge, polymer solid waste, and biomass-like solid waste, according to their variations in origins and characteristics in China. Agricultural waste (i.e., biomass) and large-scale industrial solid waste (e.g., coal waste) are not considered, because of their well-established fundamentals. Incineration is becoming the most common method of energy recovery for OSW in China, while it has to face the problems of relatively low thermal efficiency, high air pollutant emission, and the high risk of fly ash products. Compared with MSW incinerators, coal-fired power plants own efficient power generation systems and centralized air pollution control devices (APCDs). With the fact that mixed coals are widely used in existing power plants, it is of great significance to study and discuss the current status of cocombustion of OSW and coal in China. In this work, the physicochemical properties of OSW were first introduced, with a subsequent detailed summary on their co-combustion fundamentals, such as devolatilization, ignition, char reactivity, and combustion efficiency, and ash-related issues, including fouling/slagging, high-temperature corrosion, and leaching behavior of ash residue. Furthermore, pollutants emissions regarding conventional pollutant [CO, SO 2 , NO, HCI, particulate matters (PM)], heavy metals, and hazardous organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed. Some pretreatment methods to reduce the risk of co-combustion were also discussed, including pelletization, drying, torrefaction, hydrothermal carbonization, and low-temperature pyrolysis. Lastly, discussions and perspectives on the future co-combustion technology of OSW with coal were presented. This work aimed to gain systematic knowledge on the co-combustion technology of OSW and coal, providing guidelines for further applications of OSW in power plants in China, as well as other countries in the world.