Black liquor gasification (BLG) for bio-fuel or electricity production at the modern pulp mills is a field in
continuous evolution and the efforts are considerably driven by the climate change, fuel security, and
renewable energy. This paper evaluates and compares two BLG systems for methanol production: (i) oxygen
blown pressurized thermal BLG; and (ii) dry BLG with direct causticization, which have been
regarded as the most potential technology candidates for the future deployment. A key objective is to
assess integration possibilities of BLG technologies with the reference Kraft pulp mill producing
1000 air dried tonnes (ADt) pulp/day replacing conventional recovery cycle. The study was performed
to compare the systems’ performance in terms of potential methanol production, energy efficiency,
and potential CO2 reductions. The results indicate larger potential of black liquor conversion to methanol
from the pressurized BLG system (about 77 million tonnes/year of methanol) than the dry BLG system
(about 30 million tonnes/year of methanol) utilizing identical amount of black liquor available worldwide
(220 million tDS/year). The potential CO2 emissions reduction from the transport sector is substantially
higher in pressurized BLG system (117 million tonnes/year CO2 reductions) as compared to dry BLG
system (45 million tonnes/year CO2 reductions). However, the dry BLG system with direct causticization
shows better results when considering consequences of additional biomass import. In addition,
comparison of methanol production via BLG with other bio-refinery products, e.g. hydrogen, dimethyl
ether (DME) and bio-methane, has also been discussed.