282128 A Mathematical Model for a Biofuel Production Process From Macroalgae

Monday, October 29, 2012
Hall B (Convention Center )
Claudio Delpino, Chemical Engineering, Planta Piloto de Ingeniería Química (PLAPIQUI), Universidad Nacional del Sur-CONICET, Bahía Blanca, Argentina, Vanina Estrada, Chemical Engineering, Planta Piloto de Ingenieria Quimica (PLAPIQUI), Universidad Nacional del Sur - CONICET, Bahia Blanca, Argentina and María Soledad Diaz, Chemical Engineering, Planta Piloto de Ingenieria Quimica (PLAPIQUI), Universidad Nacional del Sur - CONICET, Bahia Blanca, Argentina,, Bahia Blanca, Argentina

In this paper, we review published data and past efforts towards the production of ethanol using macroalgae as raw materials. When analyzing macroalgae biomass as a source of polysaccharides, which can be directly fermented by special organisms or hydrolized into simple sugars that are fermentable by well known ethanol producing, a key fact to have into account is the absence of lignin. In the group known as "brown" algae, these polysaccharides are represented by storage molecules like laminarin and mannitol, and alginates and cellulose, which conform the amorphous and fibrillar part of the cell wall, respectively. When it comes to the so called "red" algae, the fermentable polysaccharides include cellulose and galactans (which are nowadays used for agar production), which could amount to higher ethanol yields. A biorefinery scheme is proposed and mathematically modeled based on published data  and efforts from other sources ([1], [2], [3]). The proposed biorefinery main route includes cultivation, harvesting and processing of macroalgae. Cultivation can be carried out in offshore or nearshore  “farms” for which several  technologies have been proposed, or in onshore installations, which offer an easier and more precise control of the cultivation, with higher yields, at the expense of higher capital and operating costs.   Processing of macroalgae includes succesive acid and enzymatic hydrolisis of polysaccharides and their posterior fermentation.

We formulate a mathematical model for integrated macroalgal-based biorefineries, allowing for cost, energy and water need calculations. The model also includes the possibility to allow  for several macroalgae species and origins, diverse processing routes, and several products and by-products. This allows comparison of the different alternatives, and optimization of the economical and energetic performance of the process using mathematical programming techniques. The optimization framework  is specially useful for the macroalgae context, where the integration with current algal high-value products facilities, or even the production of this high-value byproducts (i. e. agar) in the integrated biorefinery, is essential for the process economic sustainability. The model has been implemented in GAMS as a Mixed Integer Nonlinear Programming problem. Numerical results provide quantitative information and give useful insights on macroalgal-based biorefineries. At the same time, the local potential for a given processing environment can be easily evaluated. We accomplish these for several options within Argentina


[1] G. Roesijadi et al., “Techno-Economic Feasibility Analysis of Offshore Seaweed Farming for Bioenergy and Biobased Products,” 2008.
[2] T. Burton et al., “A review of the potential of marine algae as a source of biofuel in Ireland,” 2009.
[3] M. Yanagisawa et al., “Production of high concentrations of bioethanol from seaweeds that contain easily hydrolyzable polysaccharides,” Process Biochemistry, vol. 46, no. 11, pp. 2111-2116, Nov. 2011.

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