469498 Design and Economic Analysis of a Macroalgae-to-Butanol Process Via a Thermochemical Route
Design and Economic Analysis of a Macroalgae-to-Butanol Process via a Thermochemical Route
Biofuels produced from macroalgae are termed third generation biofuels and are becoming of increasing interest in the renewable fuels community. The advantages macroalgae have over first and second generation biofuel feedstocks include fast growth rates, which enable up to 4 - 6 harvest cycles per year, and the ability to be grown in the sea thus eliminating issues relating to land use and irrigation water . Despite these advantages, question marks around their economic and environmental potential remain because of uncertainties around optimal macroalgae cultivation and harvest methods as well as the technologies to convert them to fuel. The objective of this presentation is to address the question of macroalgae conversion to fuel.
One such fuel receiving increased attention is biobutanol, as it is a better alternative to bioethanol as a gasoline replacement in current automobile engines and fuel pipeline networks . Two major routes exist for biobutanol production; the biochemical route which primarily proceeds via fermentation of biomass feedstock to butanol, and the thermochemical route which proceeds via gasification of biomass feedstock to syngas and the conversion of syngas over catalysts to butanol. This work assesses a first-of-its-kind process for butanol production from macroalgae through a thermochemical pathway.
The design and simulation of different configurations was performed in Aspen Plus. In addition, the potential of the different configurations were assessed using economic and environmental metrics such as the minimum butanol selling price (MBSP), and cost of CO2 equivalent emissions (CO2e) avoided under different market scenarios. The resulting values of the metrics were then compared amongst the different configurations and also against standard literature references of similar processes. Finally, the impact that variations in key parameters have on the metrics were assessed using sensitivity analysis.
The results showed that the lowest MBSP was obtained with configurations which import natural gas and electricity as utility sources alongside the macroalgae feedstock. However these options perform poorly when the cost of CO2e avoided is factored in. On the other hand, macroalgae-only configurations provide the best potential for cost of CO2e avoided but perform poorly for the MBSP metric. Finally, evaluation of the sensitivity analyses results show that gasoline price changes have a high impact on the South Korean based plant configurations as shown in Fig. 1 .
Figure 1: Sensitivity of key parameters from their base case values on MBSP (bottom bars with hatched fill) and CCA (top bars with solid fill) of the South Korea - self-sufficient plant scenario.
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 C. Okoli, T. A. Adams, 2016. "Design and economic analysis of a macroalgae-to-butanol process via a thermochemical route". Manuscript submitted for publication, 2016.