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Enhancing Biogas Production from Lignocellulosic Materials using a Reverse Membrane Bioreactor
University of Borås, Faculty of Textiles, Engineering and Business.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
Sustainable development
Sustainable Development/Sustainability is used as a subject keyword for the thesis
Abstract [en]

Lignocellulosic biomass is one of the most abundant raw materials that can be found on earth for production of biofuels including biogas. The project work dealt with two main problems that are encountered in a continuous anaerobic digestion process which includes, cell washout and presence of inhibitors derived from the pre-treatment of lignocelluloses. The main aim of the thesis was to study the novel configuration of reverse membrane bioreactor (RMBR) with cell bag module for production of biogas from lignocellulosic material in order to retain high cell density inside the bioreactor and to study the possibility of using RMBR with cell bag module to combat the inhibitory effects of by-products derived from lignocelluloses.

The experiments were performed under anaerobic thermophillic conditions. It was observed from the results of a batch study that the biogas production from lignocellulosic hydrolysate using RMBR system with PVDF cell bag module was more efficient than the RMBR system with PES cell bag module. Based on these results a semi-continuous anaerobic digestion process was setup. The performance of encased cells in RMBR was superior to the free cell control system. The experiment was performed for a period of 160 days and the encased cells were able to produce a maximum of 2.5L of biogas per day at the organic loading rate 25.82 gCOD/L.day as compared to free cell that could produce a maximum of 0.4 L at 0.27 gCOD/L.day. The cell bag module of RMBR was also employed to investigate the effects of by-products present in lignocellulosic hydrolysate on methanogens as a solution to combat these inhibitory effects. The results revealed that the strongest inhibitory effect on methanogens was caused by hydroquinone at the concentration of 1 g/L however the RMBR system under semi-continuous anaerobic digestion process could tolerate 16g/L. The least inhibiting byproduct was found to be furfural. In the batch study over 4 g/L concentration of furfural there was only a small amount of biogas production. The results from the semi-continuous anaerobic digestion process of synthetic medium containing furfural revealed that the RMBR system could tolerate a concentration level of 30 g/L before the encased cells finally lost their activity. Thus, it can be concluded that the protective effects of RMBR system on encased cells were observed and the RMBR system could tolerate very high concentrations of inhibitors.

A study to test the performance of RMBR with novel configuration of IPC system was performed to conclude the effects of high organic loading rate on the novel IPC RMBR system. At lower OLRs the performance of IPC system and free cell system was similar. The free cell system was unable to perform at OLR 8 gCOD/L.day. In addition, the IPC system was able to perform up to OLR of 15 gCOD/L.day and produce a maximum of 623 mL/day of biogas at OLR of 15 gCOD/L.day.

Thus, with the help of the results obtained by performing these sets of experiments it can be concluded that RMBR systems with cell bag module are capable of combating the two major problems addressed above, i.e., cell wash out and inhibitory effects of by-products present in lignocellulosic materials.

Place, publisher, year, edition, pages
2016.
Keyword [en]
biogas, lignocelluloses, reverse membrane bioreactor (RMBR), high cell density
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:hb:diva-12140OAI: oai:DiVA.org:hb-12140DiVA: diva2:1093545
Available from: 2017-05-09 Created: 2017-05-08 Last updated: 2017-05-09Bibliographically approved

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