Abstract
The solid fraction obtained by mechanical separation of digestate from anaerobic digestion
plants is an attractive feedstock for the pyrolysis process. Especially in the case of digestate obtained
from biogas plants fed with energy crops, this can be considered a lignin rich residue. The aim of this
study is to investigate the pyrolytic kinetic characteristics of solid digestate. The Starink model-free
method has been used for the kinetic analysis of the pyrolysis process. The average Activation Energy
value is about 204.1 kJ/mol, with a standard deviation of 25 kJ/mol, which corresponds to the 12% of
the average value. The activation energy decreased along with the conversion degree. The variation
range of the activation energy is about 99 kJ/mol, this means that the average value cannot be used to
statistically represent the whole reaction. The Master-plots method was used for the determination of
the kinetic model, obtaining that n-order was the most probable one. On the other hand, the process
cannot be modeled with a single-step reaction. For this reason it has been used an independent
parallel reactions scheme to model the complete process.
plants is an attractive feedstock for the pyrolysis process. Especially in the case of digestate obtained
from biogas plants fed with energy crops, this can be considered a lignin rich residue. The aim of this
study is to investigate the pyrolytic kinetic characteristics of solid digestate. The Starink model-free
method has been used for the kinetic analysis of the pyrolysis process. The average Activation Energy
value is about 204.1 kJ/mol, with a standard deviation of 25 kJ/mol, which corresponds to the 12% of
the average value. The activation energy decreased along with the conversion degree. The variation
range of the activation energy is about 99 kJ/mol, this means that the average value cannot be used to
statistically represent the whole reaction. The Master-plots method was used for the determination of
the kinetic model, obtaining that n-order was the most probable one. On the other hand, the process
cannot be modeled with a single-step reaction. For this reason it has been used an independent
parallel reactions scheme to model the complete process.