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Please use this identifier to cite or link to this item:
http://hdl.handle.net/2282/743
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| Title: | Biogas feed analysis |
| Authors: | Song, Yuan |
| Issue Date: | 2008 |
| Abstract: | Biogas production is regarded as the best energy recovery process from wet organic solid wastes
(WOSW). Feed composition, storage conditions and time will influence the compositions of feed to
biogas processes. In this study, apple juice from Meierienes Juice factory was used as the model
substrates to mimic the liquid phase that can be extracted from fruit or juice industry WOSW.
A series of batch experiments were carried out with different initial feed concentrations (0, 1, 2, 5,
10 %) of apple juice mixed with a biogas culture from the local anaerobic digester (AD). The initial
feed content of 2 % and 5 % (weight %) gave the high biogas yields 55 (mL biogas per mL feed
consumed), compared to 1 % and 10 %, which gave the biogas yields of 42 (mL biogas per mL
feed consumed) perhaps due to substrate inhibition. The biogas yield data from 2 % and 5 % feed
case were used for simulation in ADM1 to estimate the substrate compositions. Measured and
estimation data from ADM1 are similar and show that the apple juice included mainly sugar, some
protein, fat and organic acids with the total sCOD = 120 g COD/L. It implies that ADM1 can be
used as a soft sensor method to estimate the substrate composition quite accurately from simple
biogas measurements in batch experiments.
Three different inoculum preparation methods were used in this study: Slurry from outlet of AD
reactor (unfiltered); Leachate from sieve filtered (pore size: 500 μm); Leachate from belt filter
process after AD reactor. The study show that the inoculum prepared from belt filter leachate was
suitable for biogas production studies and had some advantages compared to unfiltered cultures.
Micro-aeration treatment in the AD process was also tested in batch experiments. The results show
that suitable amounts of air (oxygen) supply requires careful control for micro-aeration treatment to
have a positive effect on biogas production in AD processes. An experiment of continuous flow bioreactor (CFB) for acidogenesis was also carried out to study
the feed buffer capacity/pH effect on H2 yields and consumptions. The H2 production rate was 8
mmol/L /d at pH =7.3, and 4 mmol/L /d at pH =3.7. H2 was both produced and consumed in the
reactor. pH also influenced the acid accumulation and therefore the metabolic pathways.
Five main hypotheses were tested in this study leading to the following conclusions: (1) Apple
juice can be used as a model substrate for the study of fermentation and biogas production; (2)
Food to microorganism (F/M) ratios can be used to identify the substrate overload issues or the
substrate inhibition problems; (3) Leachate from the belt filter process after the AD reactor can be
used as the inoculum for the study of biogas production processes; (4) Biogas substrate
composition can be estimated from simple batch tests and ADM1 simulations; (5) pH influences
the metabolic pathway selection of glucose fermentation. |
| Keywords: | Biogas feed analysis
CH4 production
Substrate composition estimation
ADM1
Biological H2 yields and consumptions
Glucose fermentation |
| Document type: | Master's thesis |
| URI: | http://hdl.handle.net/2282/743 |
| Appears in Collections: | Mastergradsavhandlinger i teknologi
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