Vacuum pyrolysis of intruder plant biomasses
Résumé
Biomass from three invasive plant species of the Western Karoo region in South Africa, namely Kraalbos,
Schotzbos and Asbos, was treated by vacuum pyrolysis. The influence of temperature, pyrolysis time,
pressure and initial moisture content on the bio-oil and charcoal yields were investigated. Asbos with
the largest ash content, 19.9 wt.%, gave chars with an ash content between 40 wt.% and 44 wt.% making
it difficult to use commercially. Vacuum pyrolysis of Kraalbos resulted in producing a biochar with a
HHV of 23.0–25.5 MJ/kg and an ash content of 13–19 wt.% which compared favourable with commercial
charcoal. The bio-oils from both Kraalbos and Schotzbos showed promise as potential heating oil
with a HHV of 21.6–26.9 MJ/kg. The tarry phase contained a number of phenolic compounds that can be
separated and shows promise as a feedstock for upgrading. Finally, ageing which acts on the lignocellulosic
structure of biomasses decreased the charcoal and oil yields from the vacuum pyrolysis of intruder
plants.