(636e) 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

Chinedu O. Okoli¹,
Thomas A. Adams II^1[*], Boris Brigljević² and
Jay J. Liu²

¹Department of Chemical Engineering, McMaster
University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7

²Department of Chemical Engineering, Pukyong
National University, 365 Sinseon-ro, Nam-gu, Busan 608-739,Republic of Korea

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 [1]. 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 [2]. 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 [3].

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.

REFERENCES:

[1] G. Roesijadi,
S. B. Jones, L. J. Snowden-Swan, and Y. Zhu, “Macroalgae as a biomass
feedstock: a preliminary analysis,” Pacific Northwest National Laboratory, Richland,
2010.

[2] M. Kumar and K. Gayen, “Developments in
biobutanol production: New insights,” Appl. Energy, vol. 88, no. 6, pp.
1999–2012, Jun. 2011.

[3]  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.