Mechanistic and kinetic study of the hydrothermal treatment of paunch waste.

[Display omitted] • Hydrothermal carbonization converted up to 80% of problematic paunch waste. • The mechanisms of hydrothermal treatment of paunch waste was explained. • The kinetic study revealed the reactiveness of paunch waste in hot compressed water. • Formation of aqueous phase is much faster than that of bio-oil. • Holding time can substantially affect the commercial viability of the process. Hydrothermal carbonization of paunch waste, the main wet waste generated at abattoirs, was investigated in batch mode. A mass loss of 58% was achieved at 240 °C in a flash experiment, whereas prolonging the reaction to 4 h increased it to 79%, indicating the ability of a hydrothermal medium for managing this wet waste. XRD analysis suggested that the amorphous portion of paunch waste was readily hydrolysed, whereas crystalline cellulose I was retained. Longer holding time partially destroyed the formed porous structure and halved the BET surface area from 68.1 to 37 m2 g−1. Aromatic, cyclic, and phenolic compounds were found in light bio-oil, while heavy bio-oil contained long-chain fatty acids derivatives. A reaction network was suggested containing 12 reaction pathways during the process, and lumped kinetic modelling was performed reasonably accurately. The techno-economic analysis also revealed that with a solids content of 3 wt.%, only processing time as short as 5 min can promise a positive net present value of $8.3 million, while longer residence times led to negative values. [ABSTRACT FROM AUTHOR]