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Anaerobic co-digestion of solid slaughterhouse wastes with agro-residues: Synergistic and antagonistic interactions determined in batch digestion assays
University of Borås, School of Engineering.
University of Borås, School of Engineering.ORCID iD: 0000-0003-4887-2433
University of Borås, School of Engineering.
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2014 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, 89-98 p.Article in journal (Refereed) Published
Sustainable development
The content falls within the scope of Sustainable Development
Abstract [en]

Different mixture ratios of solid cattle slaughterhouse wastes (SB), manure (M), various crops (VC), and municipal solid wastes (MSW) were investigated for biogas production. The objective was to explore possible significant synergistic effects obtained from the combination of these different substrates. The performance of the process was assessed in thermophilic anaerobic batch co-digestion assays, using a four factor mixture design and methane yield (Y-CH4) and specific methane production rate (r(scH4)) as response variables. The highest methane yield, 655 NmL CH4/g VS was obtained when equal parts (ww) of SB, M, VC, and MSW were combined, while the combination of SB, M, and MSW resulted in the highest specific methane production rate (43 NmL CH4/g VS/d). A mixture design model was fitted to data in order to appraise synergistic and antagonistic interactions. Mixing all four substrates resulted in a 31% increase of the expected yield which was calculated from the methane potential of the individual fractions, clearly demonstrating a synergistic effect due to more balanced nutrient composition enhancing the anaerobic digestion process. However, no significant antagonistic effects were observed. In order to maximize both response variables simultaneously, a response surface method was employed to establish the optimal combination of substrate mixtures. The statistical results and analysis of the biological process gave a coherent picture of the results. (C) 2014 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
Elsevier , 2014. Vol. 245, 89-98 p.
National Category
Industrial Biotechnology Chemical Engineering
Research subject
Resource Recovery
URN: urn:nbn:se:hb:diva-1834DOI: 10.1016/j.cej.2014.02.008ISI: 000335275200012Local ID: 2320/13546OAI: diva2:869912
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-03-15
In thesis
1. Biogas from slaughterhouse waste: Mixtures interactions in co-digestion
Open this publication in new window or tab >>Biogas from slaughterhouse waste: Mixtures interactions in co-digestion
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Global environmental concerns connected to the use of fossil fuels have forced the development ofalternative sustainable energy technologies. The application of anaerobic digestion, from waste streams thatcurrently have no use, can be utilized for bioenergy production. Due to the high protein and fat content,slaughterhouse waste has a high potential for biogas production. However, potential inhibitory compoundscan be formed during the degradation of the proteins and lipids, which can make the process sensitive andprone to failure. One of the ways to overcome these problems is co-digestion with carbohydrate-rich cosubstratesi.e., a mixture of agro-wastes with low protein/lipid content. This also leads to a better nutritionalbalance and enhanced methane yield due to the positive mixture interactions.

In this study, four different waste fractions, i.e., solid cattle slaughterhouse waste (SB), manure (M),various crops (VC), and the organic fraction of municipal solid waste (MSW) were investigated in monodigestionand co-digestion processes. Different mixture ratios were prepared, and the methane yield (YCH4),the specific methanogenic activity (SMA), and a kinetic parameter (k0) were determined using the batchdigestion assays at thermophilic conditions (55oC). The SB had a lower degradation rate and lower SMAcompared with those of the other samples. In order to investigate the effect of the temperature, a selectedmixture ratio was also digested at mesophilic conditions (37oC), which resulted in a decrease in YCH4 and inthe kinetic parameters, specific methane production rate (rsCH4), and k0, by up to 57% compared to thoseobtained at the thermophilic conditions. During the next part of the work, a four-factor mixture design wasapplied aiming to obtain possible synergetic or antagonistic effects. The performance of the process wasassessed using YCH4and rsCH4as the response variables. Mixing all four of the substrates resulted in a 31%increase in the YCH4compared to the expected yield calculated on the basis of the methane potential of theindividual fractions and 97% of the theoretical methane yield, clearly demonstrating a synergistic effect.Nevertheless, antagonistic interactions were also observed for certain mixtures. In order to maximize boththe response variables simultaneously, a response surface method was employed to find the optimalcombination for the substrate mixture.

The impact of the mixture interactions, obtained in the batch operation mode, was also evaluated undersemi-continuous co-digestion. Digestion of the SB as the sole substrate failed at an organic loading rate of0.9 gVS L-1d-1, while stable performance with higher loadings was observed for mixtures that displayedsynergy earlier during the batch experiments. The combination that showed the antagonistic effects resultedin unstable operation and poor representation of methanogens. It was proved that synergetic or antagonisticeffects observed in the batch mode could be correlated to the process performance, as well as to thedevelopment of the microbial community structure during the semi-continuous operation.

In the last part of the work, the response of the methanogenic biomass to the consecutive feeding applied inthe batch assays was evaluated regarding process parameters such as YCH4, SMA, and degradation kinetics.The objective was to examine whether there is a possibility to correlate these findings to the expectedprocess performance during the long-term operation. Digestion of the SB alone showed a total inhibitionafter the second feeding, which is in correlation with the failure observed during the semi-continuous mode.Furthermore, enhanced SMA was observed after the second feeding in those mixtures that showed synergyin the previous batch assays as well as a good process performance during the semi-continuous operation.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2015
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 75
Slaughterhouse waste, Agro-Waste, Co-digestion, Synergistic effects, Methanogenic community structure
National Category
Environmental Biotechnology
Research subject
Resource Recovery
urn:nbn:se:hb:diva-847 (URN)978-91-87525-85-8 (ISBN)978-91-87525-86-5 (ISBN)
Public defence
2015-12-10, E310, Allégatan 1, Borås, 10:00 (English)
Available from: 2015-11-25 Created: 2015-10-02 Last updated: 2015-12-18Bibliographically approved

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