A kinetic study of roadside grass pyrolysis and digestate from anaerobic mono-digestion

The aim of this research is to evaluate the thermogravimetric behaviour of roadside grass and its digestate obtained from mesophilic anaerobic mono-digestion by quantifying its impacts on biomass composition and properties. Thermogravimetric measurements were conducted in a laboratory furnace under nitrogen flowrate of 100 mL/min in the temperature range from 35 to 800 °C at five different heating rates of 2.5, 5, 10, 15 and 20 °C/min. Friedman and Kissinger-Akahira-Sunose differential and integral isoconversional models were applied to determine the distributions of activation energies and modified pre-exponential factors per reacted mass (degree of conversion). The investigation demonstrated that anaerobic digestion of roadside grass can be used to generate biochar-richer material (with significantly greater yield of final residues after pyrolysis) with less energy required for subsequent pyrolysis in comparison with raw roadside grass.