Techno-Economic Analysis of an Integrated Approach for Bio-Methanol Production from Micro-Algae in the UAE

In this proposed research, an integrated approach is taken to produce bioenergy from micro- algae, by modelling bio-methanol production through gasification of biomass using Aspen Plus. The key stages of the process are gasification, syngas post treatment, methanol synthesis followed by purification. The developed model performance is then evaluated for three different types of micro-algal species: (1) S. Acuminatus (2) N. Oculata and (3) S. Almeriensi. The performance of the micro-algal species was also compared with a plant biomass (pine). The simulation results were found to be comparable to experimental data available in literature.

S. Acuminatus was found to produce the greatest amount of bio-methanol and the greatest HHV value under identical conditions. A sensitivity analysis was conducted to evaluate the optimum gasification temperature for obtaining maximum bio-methanol yield, for each of the feedstocks. The optimum temperature was found to be 860; 880 and 860 °C for S. Almeriensi, N. Oculata, and S. Acuminatus respectively.

Since obtaining specific raw material costs for each micro-algal species was difficult, a general feedstock of Chlorella vulgaris is considered. A sensitivity analysis was conducted for wide range of bio-methanol selling prices and two Chlorella vulgaris feedstock prices ($269 and $45 per ton). The average bio-methanol selling price is $770 per ton. However, when applied as a shipping fuel, the cost of bio-methanol increases manifold to $3,336 per ton. Hence, the best scenario is when methanol is sold at the bunker prices. An IRR of 525% was recorded even when the raw material price was as high as $269 per ton. The worst case was identified to be when the bio-methanol price was $693 per ton. Minimum profitability was obtained with a payback time of 14 years (without 3-year construction) with a plant lifespan of 20 years. An IRR of only 2.6 % was obtained. Considering the standard average price of $770 per ton, an ROI of 2.6% and 13.2% was noted when raw material prices were $269 and $45 per ton, respectively. Therefore, the plant can be classified as feasible.