Upgradation of Nostoc punctriforme under subcritical conditions into liquid hydrocarbons (bio-oil) via hydro-deoxygenation: Optimization and engine tests

In this present study, hydro-deoxygenation (HDO) process was performed to upgrade the liquefied bio-oil of Nostoc punctriforme biomass. The engine performance and emission properties of the enriched bio-oil and blends (with diesel) were evaluated. The HTL resulted in highest bio-oil yield of 47.5 wt% at a temperature of 300 degrees C at 60 min with calorific value of 32.5 MJ/kg. At 60 min and temperature of 300 degrees C with 1 wt% of heterogeneous catalyst the upgraded HDO-bio-oil yield reached 38.4 wt% with deoxygenation percentage of 70%. The properties of upgraded bio-oil are HHV of 44.74 MJ/kg, Kinematic viscosity of 6.23 mm(2)/s and density 923 kg/m(3) respectively. The response surface methodology (RSM) was used for modeling and optimizing the upgraded biooil yield. The optimized RSM conditions for upgraded bio-oil yield (44.5 wt%) are temperature of 280 degrees C, catalyst load of 0.6 wt%, and time of 120 min. The physiochemical properties of upgraded bio-oil are in agreement with ASTM standards. Equal proportion of bio-oil to diesel (D50: B50) reduced the brake thermal efficiency to 6.66% with reduced NOx emission and slight increase in CO emission. This study highlights that microalga fuels are better renewable energy resource with reduced greenhouse gas emission.

Automated summary

In this study, the HDO process was used to upgrade liquefied bio-oil from Nostoc punctriforme biomass, with RSM optimization resulting in bio-oil properties meeting ASTM standards. Mixing bio-oil with diesel at a 50% ratio reduced brake thermal efficiency while decreasing NOx emissions and slightly increasing CO emissions. This research emphasizes the potential of microalgae fuels as a renewable energy resource with reduced greenhouse gas emissions.