Bio-oil production from hydrothermal liquefaction of waste Cyanophyta biomass: Influence of process variables and their interactions on the product distributions

Hydrothermal liquefaction (HTL) of waste Cyanophyta biomass at different temperatures (factor A, 260–420 °C), times (factor B, 5–75 min) and algae/water (a/w) ratios (factor C, 0.02–0.3) by single reaction condition and Response Surface Method (RSM) experiments was investigated. By single reaction condition runs, maximum total bio-oil yield (29.24%) was obtained at 350 °C, 60 min and 0.25 a/w ratio. Maximum bio-oil HHV of 40.04 MJ/kg and energy recovery of 51.09% was achieved at 350 °C, 30 min, 0.1 a/w ratio and 350 °C, 60 min, 0.25 a/w ratio, respectively. RSM results indicate that effect of AB interaction was significant on light bio-oil yield. Both AC and AB had more remarkable influence than BC on heavy bio-oil yield and aqueous total organic carbon (TOC) recovery whereas BC was noticeable on ammonia nitrogen (NH₃N) recovery in aqueous products. By model-based optimization of highest bio-oil yield, the highest bio-oil yield reached 31.79%, increasing by 8.72% after RSM optimization, and light and heavy bio-oil yield was 17.44% and 14.35%, respectively. Long-chain alkanes, alkenes, ketones, fatty acids, phenols, benzenes, amides, naphthalenes were the main components in light bio-oil. Some alcohols, phenols and aromatics were primarily found in heavy bio-oil. Solid residue after HTL consisted of numerous microparticles (～5 μm) observed by Scanning Electron Microscopy (SEM). Energy Dispersive Spectrometer (EDS) analysis shows these particles primarily contained C, O, Mg, P and microelements, derived from Cyanophyta cells.     

Reutilization potential of antibiotic wastes via hydrothermal liquefaction (HTL): Bio-oil and aqueous phase characteristics

Hydrothermal liquefaction (HTL) technology was employed to investigate the feasibility of recovering energy from penicillin mycelial waste (PMW) with the help of TG, Py-GC/MS and GC-MS techniques; meanwhile, the nutrients in aqueous phase were also analyzed by spectrophotometry methods. The effects of operating conditions, including hydrothermal temperature (240–300 °C), duration time (20–60 min), total solid ratio (5–15%) and their interactive reactions were concurrently evaluated via response surface methodology. Results demonstrated that operating temperature was found to be the dominant variable affecting the HTL of PMW. Based on the optimal conditions of 298 °C, 60 min and 14.85%, heavy oil derived from PMW was comparable with algal-derived bio-oil as it possessed the highest energy recovery efficiency (42.95%) with a calorie value of 32.84 MJ/kg and a yield of 24.93%. GC/MS results indicated that heavy oil mainly consisted of N-containing compounds (36.73%) and aromatic compounds (31.07%), which might be contributed to the hydrolysis of protein and the aromatization of intermediates, respectively. Besides, more than 65% of nitrogen and 40% of carbon were enriched in aqueous phase, suggesting the possibility of further recycling for algae cultivation, fermentation and anaerobic digestion.