Design and Simulation of Biofuel Production from Pyrolysis of Brown Macroalgae

In recent years, thermochemical conversion processes such as pyrolysis have been greatly studied for biofuel production. Traditional feedstocks which have been considered in this research include various kinds of terrestrial biomaterials such as food crops (1^st generation biofuels) and woody biomass (2^nd generation biofuels). However, pyrolysis of 3^rd generation biomass i.e., microalgae and macroalgae has only been recently studied. As the chemical composition of algae and their seasonal variation differ greatly from terrestrial biomass, especially in large water and ash content, the process of pyrolysis has to be redesigned and evaluated for this particular application. Conceptual process design coupled with computer assisted process simulation is a widely accepted approach for techno-economical evaluation of new production processes for novel feedstocks.

This study aims to simulate and evaluate the pyrolysis conversion pathway of brown macroalgae and subsequent biofuel production on an industrial scale (14,400 tons year^-1 feed), using Aspen Plus V8.6 simulator. Validity of the simulation is backed up by bench-scale experimental data for indirectly heated, non-catalytic pyrolysis process of brown marine alga Saccharina japonica as well as with experimental data for upgrading steps. This study presents the extent of modifications for applying this particular feedstock to thermochemical conversion and biofuel production. Primary differences, compared to similar processes using terrestrial biomass include: (i) pretreatment (mineral content removal and drying), (ii) pyrolysis and optimization of combustion, as well as (iii) the number and severity of stabilization and upgrading steps. Additionally, simulation results demonstrate the overall energy requirement, as well as provide indications of economic viability of the process. Ultimately, the strategic points of integration with bioconversion platform are determined.