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  • 1.
    Pagés Diaz, Jhosané
    University of Borås, Faculty of Textiles, Engineering and Business.
    Biogas from slaughterhouse waste: Mixtures interactions in co-digestion2015Doctoral 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.

  • 2.
    Pagés Díaz, Jhosané
    et al.
    University of Borås, School of Engineering.
    Pereda Reyes, Ileana
    Lundin, Magnus
    University of Borås, School of Engineering.
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Co-digestion of different waste mixtures from agro-industrial activities: Kinetic evaluation and synergetic effects2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 23, 10834-10840 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield (YCH4), specific methanogenic activity (SMA) and a kinetic parameter (k0) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with YCH4 of 664; 582 NmL CH4/gVSsubstrate, as well as SMA of 0.12; 0.13 gCODNmLCH4/gVSinoculum/d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in YCH4 by up to 43%, compared with values calculated from YCH4 of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed.

  • 3.
    Pagés Díaz, Jhosané
    et al.
    University of Borås, School of Engineering.
    Pereda Reyes, Ileana
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Pérez Olmo, Jesús
    An approach to the codigestion process of solid slaughterhouse waste, manure, various crop and municipal solid waste2011Conference paper (Other academic)
    Abstract [en]

    A codigestion process was evaluated when mixing different ratios of agro-industrial residues, i.e. slaughterhouse waste (SB); manure (M); various crop residues (VC); and municipal solid waste (MSW). Methane yield (YCH4) and specific methanogenic activity (SMA) were determined by anaerobic batch digestion of the different substrates and substrate mixtures. The performance of the codigestion was also evaluated by kinetics (k0) based on the methane production rate. The investigated residues and their mixtures were found to have high potentials for the production of biogas. The codigestion process showed to be a feasible option with positive influence in both energy production and environmental care. Taking into account significance differences, the best results were obtained with a mixture ratio of 1:3:4:0.5 based on the w/w content of SB, M, VC, and MSW, respectively, which showed a proper combination of high values in YCH4, SMA and k0 during the anaerobic process. The effect of temperature suggested that thermophilic conditions are suitable to treat these residues. Response variables were severely affected by mesophilic conditions, diminishing in at least 45% of the thermophilic value when a mixture ratio of 2:3:3:0 based on the w/w content of SB:M:VC:MSW was selected. It is suggested to study the influence of individual component within the mixture for every response variable. Consecutive feedings are also suggested in order to step forward to continuous process and evaluate possible inhibitions.

  • 4.
    Pagés Díaz, Jhosané
    et al.
    University of Borås, School of Engineering.
    Pereda Reyes, Ileana
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Lundin, Magnus
    University of Borås, School of Engineering.
    Anaerobic co-digestion of solid slaughterhouse wastes with agro-residues: Synergistic and antagonistic interactions determined in batch digestion assays2014In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, 89-98 p.Article in journal (Refereed)
    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.

  • 5.
    Pagés-Díaz, J.
    et al.
    University of Borås, School of Engineering.
    Pereda-Reyes, I.
    Sárvári-Horváth, Ilona
    University of Borås, School of Engineering.
    Lundin, M.
    University of Borås, School of Engineering.
    Synergistic and antagonistic interactions during anaerobic co-digestion of slaughterhouse wastes, manure, various crop and municipal solid waste residues2013Conference paper (Other academic)
  • 6.
    Pagés-Díaz, J.
    et al.
    University of Borås, School of Engineering.
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Pérez-Olmo, J.
    Pereda-Reyes, I.
    Co-digestion of bovine slaughterhouse wastes, cow manure, various crops and municipal solid waste at thermophilic conditions: a comparison with specific case running at mesophilic conditions2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 67, no 5, 989-995 p.Article in journal (Refereed)
    Abstract [en]

    A co-digestion process was evaluated when mixing different ratios of agro-industrial residues, i.e. bovine slaughterhouse waste (SB); cow manure (M); various crop residues (VC); and municipal solid waste (MSW) by anaerobic batch digestion under thermophilic conditions (55 °C). A selected study case at mesophilic condition (37 °C) was also investigated. The performance of the co-digestion was evaluated by kinetics (k(0)). The best kinetic results were obtained under thermophilic operation when a mixture of 22% w/w SB, 22% w/w M, 45% w/w VC and 11% w/w MSW was co-digested, which showed a proper combination of high values in r(s)CH(4) and k(0) (0.066 Nm(3)CH(4)/kgVS*d, 0.336 d(-1)) during the anaerobic process. The effect of temperature on methane yield (Y(CH4)), specific methane rate (r(s)CH(4)) and k(0) was also analyzed for a specific study case; there a mixture of 25% w/w of SB, 37.5% w/w of M, 37.5% of VC and 0% of MSW was used. Response variables were severely affected by mesophilic conditions, diminishing to at least 45% of the thermophilic values obtained for a similar mixture. The effect of temperature suggested that thermophilic conditions are suitable to treat these residues.

  • 7.
    Pereda Reyes, Ileana
    et al.
    Centro de Estudio de Ingenieria de Procesos Study Center of Process Engineering (CIPRO), High Polytechnic Institute “José Antonio Echeverría”.
    Pagés Díaz, Jhosané
    University of Borås, Faculty of Textiles, Engineering and Business.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Anaerobic Biodegradation of Solid Substrates from Agroindustrial Activities—Slaughterhouse Wastes and Agrowastes2015In: Biodegradation and Bioremediation of Polluted Systems -: New Advances and Technologies / [ed] Rolando Chamy, Francisca Rosenkranz and Lorena Soler, Croatia: INTECH, 2015, 31-64 p.Chapter in book (Other academic)
    Abstract [en]

    Solid wastes from the meat industry are produced in large amounts resulting in a negative impact on the environment if not properly treated. Due to their high content of proteins and fats, these residues are excellent substrates for anaerobic digestion which holds high potential for methane yield. However, possible toxic compounds may be formed during its biodegradation with a consequent failure of the process under long-term operation. The anaerobic co-digestion of such residues with other co-substrates as those generated in agricultural activities has been proposed as a good alternative to overcome these problems. Nevertheless, today there is very little knowledge to assess on mixture interactions connected to wastes composition, biodegradability, and the kinetics of the anaerobic process when complex materials are utilized in ternary and quaternary mixture, specifically when co-digesting solid cattle slaughterhouse waste with agrowaste. It is therefore important to select the right combination of substrates and ratios to obtain synergy instead of antagonism in those mixtures. This chapter aims to provide an overview of the anaerobic digestion of solid slaughterhouse waste and agrowaste, as well as the influence of mixture interactions on its biodegradation.

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