(82d) Design and Analysis of the Integrated Process for Algae Conversion to Mix Alcohols

Yue Zhang, Abhay Athaley, Marianthi Ierapetritou

Department of Chemical and Biochemical Engineering, Rutgers - The State University of New Jersey

Petroleum is the main raw material for the production of most commonly used fuels and chemicals. However, due to exhausting resources and emerging environmental issues from oil industry, alternative production paths have been investigated. Biomass sources are among the alternatives with the potential to produce both chemicals and fuels^[1]. Particularly, algae has attracted a lot of interest as a third generation biomass that contains no lignin, and requires no land or fertilizer ^[2].

The acceptance of bio-products in the market closely relates to the competitiveness with petroleum-based products not only in terms of economics but also in terms of process sustainability. A large number of researches have focused on the biomass conversion to biofuel^{[3, 4]} and the MixAlco® process is a widely studied bio-refining technology which can achieve this goal. The MixAlco® process can convert any biodegradable material into mixed alcohol fuels ^[5-7]. The ketonization route and the esterification route are the two main routes for MixAlco® process, and their economic, energy, and carbon footprint assessments have been discussed^[8]. In our work, we investigate and integrate the novel fermentation process with the two downstream process to produce higher carbon alcohols with better efficiency. A synthetic syntrophic consortia of Clostridium kluyveri and Clostridium ljungdahlii is applied to the fermentation process^[9-11]. The co-existence of these two microbes can enable fast and efficient utilization of carbon and electrons in the substrates by importing additional electrons as needed from H₂.

This work uses techno-economic analysis and life cycle assessment to design and evaluate the production alternatives for producing mix alcohols. The detailed process flowsheet is developed and simulated using Aspen Plus. Four different routes are simulated to produce alcohol mixture: 1) Ketonization Route; 2) Ketonization with Novel Fermentation Route; 3) Esterification Route; and 4) Esterification with Novel Fermentation Route. Heat integration and economic analysis is carried out to calculate the minimum product selling price of the alcohols for each route. Sensitivity analysis is performed to analyze the bottlenecks of each route and to compare the cost of the products with fluctuating cost of algae and capacity of the plant. To check the competitiveness of the above routes in terms of sustainability, Life Cycle Analysis is carried out using SimaPro®. The results with respect to carbon production and water consumption are discussed and compared to the current oil-based processes.

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