Life cycle assessment of biochar from two-step torrefaction and pyrolysis of microalgal biomass

• Main Author: Ko, Sophia C.
• Format: text
• Language: English
• Published: Animo Repository 2024
• Subjects: Biochar; Biomass energy; Life cycles (Biology); Biochar—Production control; Biomechanical Engineering; Engineering; Mechanical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_mecheng/16; https://animorepository.dlsu.edu.ph/context/etdm_mecheng/article/1025/viewcontent/Final_Thesis_KO__08_03_24_.pdf
• Institution: De La Salle University

This study explored the sustainable production of microalgal biochar for graphite applications through a life cycle assessment (LCA) of 12 scenarios varying in CO2 source, pre-treatment methods, and pyrolysis temperature. Biomass subjected to two-step torrefaction and pyrolysis at 700°C has the highest carbon content (62.50 wt%), followed by 600°C (62.155 wt%), crucial for graphite application. Scenarios utilizing CO2 from flue gas exhibited net negative greenhouse gas (GHG) emissions (-155 to -263 kg CO2-eq), with pyrolysis as the hotspot. Conversely, scenarios using CO2 from gas tanks resulted in positive GHG emissions (600-708 kg CO2-eq), with cultivation as the hotspot. Scenario i, employing flue gas CO2 and the two-step process, emerged as the most environmentally favorable (-256.165 kg CO2-eq) with desirable biochar properties. Future research should explore carbon capture technologies, renewable energy integration, techno-economic analyses, process scale-up, and expanded system boundaries to develop a comprehensive and sustainable microalgal biochar production process.