Hydrogen production from biomass by integrating thermochemical and biological processes

Orozco-Pulido, Rafael L. (2012). Hydrogen production from biomass by integrating thermochemical and biological processes. University of Birmingham. Ph.D.

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Abstract

The purpose of this research was to contribute to the development of H\(_2\) production technologies from biomass. The study integrated thermochemical processes to achieve biomass hydrolysis with biological methods to then obtain H2 by the fermentation of these hydrolysates using E. coli.
Different strains of E. coli were tested under controlled conditions in 3 L scale fermentations with the aim to find the most useful strain for the fermentation process in terms of H\(_2\) produced and the subsequent hydrogen production potential of the organic acid co-products in a downstream photofermentation. Among the strains tested FTD89, FTD67 and RL009 gave the best results, however ethanol was successfully abolished by strain RL009 making this strain more suitable for long term fermentations.
Model polysaccharide compounds such as starch and cellulose, and representative food and lignocellulosic wastes were hydrolysed in hot compressed water in the presence of CO\(_2\) under pressure and various temperatures to produce hydrolysates with high sugar content suitable for fermentation for H\(_2\) production. Optimum hydrolysis conditions for maximum sugar yields for each compound were determined. Fermentation of the obtained hydrolysates yielded acceptable amounts of H\(_2\) after their ‘detoxification’ with activated carbon (AC), comparable to H\(_2\) yielded by the glucose controls in all cases. The maximum yield of glucose after HCW treatment was obtained from starch at 200 °C yielding 548 g C.kg C initial starch\(^{-1}\); maximum glucose yield from cellulose was 225 g C.Kg C initial cellulose\(^{-1}\) obtained from cellulose hydrolysis at 250 °C, and the glucose yield from food waste was 45.5 g.g food waste\(^{-1}\). The main degradation product (DP) from these hydrolysates was 5 Hydroxymethylfurfural (5-HMF), whereas the main DP obtained from the lignocellulosic wastes was Furfural. Both were successfully removed by AC treatment.
The best hydrolysate obtained from wastes was evaluated for H\(_2\) production at 3 L scale. Despite obtaining low H\(_2\) yields improvements would be possible and are discussed. Fermentations for H\(_2\) production at pilot plant scale were also trialled, indicating key areas for future development for successful scale up.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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