Dynamic Elemental Thermal Analysis (DETA) - A characterisation technique for the production of biochar and bio-oil from biomass resources

A novel thermal analysis technique - Dynamic Elemental Thermal Analysis (DETA) - is demonstrated for the characterisation of biomass. The technique provides a unique characterisation of the pyrolysis streams by conversion into combustion products using a custom built downstream O2 lance. The result is a continuous characterisation of evolving total volatiles, light gases and tars and solid char, in terms of the elements CHNOS, with pyrolytic heating. The condensed tars were also characterised as CHNOS with boiling point. The generated suite of integrated data provided quantitative mass yields and elemental compositions that compares well with standard analytical methods. The results were used to estimate the thermal properties of the biochar and the heat of combustion of the volatile streams (i.e. total volatiles and gas only), allowing a dynamic evaluation of the energy balance of a biochar generation process. At an illustrative temperature of 500 °C for a Spotted Gum biomass, 17% of the biomass carbon is retained in the biochar. The results are used to estimate the potential revenue from each product of the heating process. The economic assessment showed that bio-oil (being the largest fraction) would provide the greatest income stream as either renewable electricity or when sold as crude liquid. The sequestration of carbon as biochar would be the smallest income stream for a carbon price of $23/tonne CO2 (around 4% total revenue). Overall, the DETA technique was shown to provide data suitable for assessment and optimisation of a biochar production technology.