Cellulosic bioethanol – how to pick the optimal process layout?

Novozymes has weighed the advantages and challenges of how to move forward with the development of cellulosic biofuel technology, and is setting the direction for process technology developed in our R&D labs. In absence of any commercially viable processes, Novozymes has developed a sophisticated model that allows us to see the tradeoffs through process alterations. By changing model parameters, including enzyme dose, hydrolysis time, and total solids level, we are able to accurately simulate different scenarios, including operational and capital costs – an important tool when working with partners on process optimization.

We have simulated various process designs in our model, such as simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), with promising conclusions. SSF is the industry standard for starch-based bioethanol, but shows suboptimal conditions for cellulosic feedstocks. In contrast, SHF allows greater ethanol yields in a shorter time, since enzymes and yeast are able to operate under optimal conditions. Novozymes has conducted sophisticated modeling to provide insight into the process of balancing these conditions with costs; Fast Fermentation is the first concept to be developed using this insight, where enzyme hydrolysis time is extended and fermentation time is compressed. This is a potential way to make SHF work and to share the cost forecast in cellulosic conversion processes.

Undoubtedly, the industry faces challenges in moving towards commercialization of cellulosic biofuel – but exciting developments continue to move us closer to commercial viability. Novozymes’ modeling competencies enable us to understand trade-offs in process design, which in turn drives our development work with our partners. We have found that the dedicated hydrolysis separate from fermentation allows better enzyme performance and a potentially better overall process design; our Fast Fermentation concept is a promising solution for C5 & C6 sugar fermentation that could help to enable the cellulosic ethanol industry.

This information is based on a presentation given by Cynthia Bryant, Novozymes Global Marketing Manager, Biofuels, at the Next Generation Biofuels Markets conference in Amsterdam in September 2009.

Source: Novozymes

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