Carbonisation and oxidation of biosolid through pyrolysis and oxidative pyrolysis for CO2 adsorption with biosolid-derived biochar: kinetic analyses

Abstract

Carbon dioxide (CO2), the primary greenhouse gas causing global warming, has seen an exponential increase in emissions due to the excessive use of fossil fuels in anthropogenic activities. To provide a possible solution to the increasing CO2 emissions, this thesis presents an experimental and theoretical analysis of utilising biosolid, a heterogeneous mixture formed during the wastewater treatment process to produce biochar for CO2 adsorption.

The pyrolysis of biosolid is conducted under different heating rates and the mass loss data obtained from thermogravimetric analysis is analysed to characterise the thermal decomposition behaviour of biosolid. The kinetic model is evaluated by using the master plots method and the kinetic parameters for corresponding conversion are determined by using isoconversional methods and a distributed activation energy model.

To facilitate the establishment of large-scale pyrolysis facilities for biosolids and provide a better understanding of the effect of air concentration on the kinetic parameters and the formation of biochar, the oxidative pyrolysis of biosolids under different air concentrations is performed.

This thesis also presents the adsorption kinetic analysis of the biosolid-derived biochar for CO2 adsorption. Through the process of characterising the CO2 adsorption process of the biosolid-derived biochar, its adsorption capacity, reusability, and diffusion mechanisms are determined. The activation energy value computed demonstrates that the adsorption process can be categorised as physisorption. The biochar samples produced from pyrolysis and oxidative pyrolysis maintain 85-84% reusable efficiency after five cycles.

The findings of this thesis are expected to provide alternative disposal strategies to the currently unsustainable management of ever-increasing biosolid production while offering an economical solid-adsorbent alternative for CO2 adsorption.