Volume 11 Issue 3 ( September 2024)

The studies regarding macroalgae and microalgae treated under Sub-critical Water Gasification (SbWG) especially their behaviour as mixed feedstock to produce H2 are still rarely found in the literature. Therefore, this study elaborated the characteristics of hydrogen gas production from single macroalgae Padina sp [P] and the impact of adding microalgae Nanochloropsis sp [N] or Spirulina sp [S] as mixed algae feedstock [NP] and [SP]. The SbWG were conducted in a high- temperature and pressure reactor at 300, 350, 400 ⁰C for 30, 60, and 90 minutes. It was found that the addition of microalgae to macroalgae feedstock under SbWG at 400 oC and 90 minutes showed a negative impact on gas yield i.e 17.5% from single macroalgae feedstock [P] decreased to 4.75% and 14.34% for single feedstock [NP] and [SP] respectively. However, it is interesting that the hydrogen from the [NP] treated at 400 °C was higher (7.4%) than from single macroalgae [P] (3.5%). It is distinctly possible that the impact of microalgae addition to macroalgae feedstock in producing gas and H2 under SbWG depends on the composition of the microalgae itself, microalgae with significant carbohydrate content leading to higher H2 yield despite lower overall gas production compared to single feedstock of macroalgae.

Keywords: macroalgae; microalgae; hydrogen; Sub-critical Water Gasification.