(2024) Science of the Total Environment_Effects of water washing and KOH activation for upgrading microalgal torrefied biochar

Zhang C.; Fang J.; Chen W.-H.; Kwon E.E.; Zhang Y.

(Elsevier B.V.) Science of the Total Environment ISSN: 489697 Vol.921 Issue. Article No.171254 DOI: 10.1016/j.scitotenv.2024.171254

Torrefaction is an effective pathway for microalgal solid biofuel upgrading, and alkali metal activation is also an efficient method to enhance fuel properties. This study explores the comparison of torrefaction alone and KOH activation combined with torrefaction to determine a better operation for biochar production from the microalga Nannochloropsis Oceanica. The results indicate that the HHV ranges of KOH-activated biochar and unactivated biochar are 25.611-32.792 MJ·kg^-1 and 25.024-26.389 MJ·kg^-1, respectively. Furthermore, KOH-activated biochar is better than unactivated biochar, with less residue, broader pyrolysis and combustion temperature ranges, higher elemental carbon, and less combined carbon. Moreover, KOH-activated biochar is close to the unactivated one from the viewpoint of expense calculation and life cycle assessment and thus possesses a better comprehensive performance. Overall, KOH activation is an efficient method for upgrading microalgal solid biofuel. The results are conducive to exploring further modification of microalgal solid biofuel production with better properties, thus leading to a greener and more efficient approach for upgrading fuel performance. © 2024 Elsevier B.V.

This work was supported by high-level talent introduction project of Northeast Agricultural University . The authors also acknowledge the financial support of the technological project of Heilongjiang Province “the open competition mechanism to select the best candidates” 2022ZXJ05C02 , and Heilongjiang Provincial Key Laboratory of Soil Protection and Remediation for this research. The authors also acknowledge the financial support of the National Science and Technology Council, Taiwan , under the grant numbers NSTC 112-2218-E-006-025 - and NSTC112-2218-E-002-052 - for this research.