| 1. |
- Axelsson Bjerg, Mette, et al.
(författare)
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Moderate thermal post-treatment of digestate to improve biomethane production from agricultural- and food waste
- 2024
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Ingår i: Bioresource Technology Reports. - : ELSEVIER. - 2589-014X. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to assess the feasibility of moderate thermal treatment (70 ◦C for one hour) of digestate in combination with post-digestion targeting residual biomethane potentials from three full-scale biogas plants digesting food waste (FW), agricultural waste (AW) and a mixture of AW and manure (AWM). Dissolved organic carbon (DOC), biomethane production, and digestate quality were investigated. For the study six laboratory-scale continuously stirred tank biogas reactors working as post-digesters, with thermally-treated and non-treated digestate were used. DOC for thermally-treated digestates increased significantly (t-test, p < 0.05); FW-digestate (110–200 %), AW-digestate (24–92 %) and for AWM-digestate (4–73 %). Indexes for corresponding DOC quality showed lower apparent organic molecular weights and decreased aromaticity (with the exception of FW-digestate). Thermal treatment of digestate improved the biomethane production during post-digestion by 21–22 % (FW-digestate) and 9 % (AW-digestate). For AMW-digestate no clear positive effect was observed, most likely due to biogas plant operational process disturbances.
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| 2. |
- Ekstrand, Eva-Maria, 1985-, et al.
(författare)
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Identifying targets for increased biogasproduction through chemical and organicmatter characterization of digestate from full‑scale biogas plants : what remains and why?
- 2022
-
Ingår i: Biotechnology for Biofuels and Bioproducts. - London, United Kingdom : BioMed Central. - 2731-3654. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: This study examines the destiny of macromolecules in different full-scale biogas processes. From previousstudies it is clear that the residual organic matter in outgoing digestates can have significant biogas potential,but the factors dictating the size and composition of this residual fraction and how they correlate with the residualmethane potential (RMP) are not fully understood. The aim of this study was to generate additional knowledge of thecomposition of residual digestate fractions and to understand how they correlate with various operational and chemicalparameters. The organic composition of both the substrates and digestates from nine biogas plants operating onfood waste, sewage sludge, or agricultural waste was characterized and the residual organic fractions were linked tosubstrate type, trace metal content, ammonia concentration, operational parameters, RMP, and enzyme activity.Results: Carbohydrates represented the largest fraction of the total VS (32–68%) in most substrates. However, inthe digestates protein was instead the most abundant residual macromolecule in almost all plants (3–21 g/kg). Thedegradation efficiency of proteins generally lower (28–79%) compared to carbohydrates (67–94%) and fats (86–91%).High residual protein content was coupled to recalcitrant protein fractions and microbial biomass, either from thesubstrate or formed in the degradation process. Co-digesting sewage sludge with fat increased the protein degradationefficiency with 18%, possibly through a priming mechanism where addition of easily degradable substrates alsotriggers the degradation of more complex fractions. In this study, high residual methane production (> 140 L CH4/kgVS) was firstly coupled to operation at unstable process conditions caused mainly by ammonia inhibition (0.74 mgNH3-N/kg) and/or trace element deficiency and, secondly, to short hydraulic retention time (HRT) (55 days) relative tothe slow digestion of agricultural waste and manure.Conclusions: Operation at unstable conditions was one reason for the high residual macromolecule content andhigh RMP. The outgoing protein content was relatively high in all digesters and improving the degradation of proteinsrepresents one important way to increase the VS reduction and methane production in biogas plants. Post-treatment
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| 3. |
- Feiz Aghaei, Roozbeh, et al.
(författare)
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Key performance indicators for biogas production : methodological insights on the life-cycle analysis of biogas production from source-separated food waste
- 2020
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 200
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Tidskriftsartikel (refereegranskat)abstract
- The anaerobic digestion of food waste can not only enhance the treatment of organic wastes, but also contributes to renewable energy production and the recirculation of nutrients. These multiple benefits are among the main reasons for the expansion of biogas production from food waste in many countries. We present methodological insights and recommendations on assessing the environmental and economic performance of these systems from a life-cycle perspective. We provide a taxonomy of the value chain of biogas from food waste which describes major activities, flows, and parameters across the value chain with a relatively high detail. By considering the multiple functions of biogas production from food waste, we propose a few key performance indicators (KPI) to allow comparison of different biogas production systems from the perspectives of climate impact, primary energy use, nutrients recycling, and cost. We demonstrate the operational use of our method through an example, where alternatives regarding the heat supply of the biogas plant are investigated. We demonstrate how global and local sensitivity analyses can be combined with the suggested taxonomy and KPIs for uncertainty management and additional analyses. The KPIs provide useful input into decision-making processes regarding the future development of biogas solutions from food waste. (C) 2020 Elsevier Ltd. All rights reserved.
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| 4. |
- Feizaghaii, Roozbeh, 1975-, et al.
(författare)
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The biogas yield, climate impact, energy balance, nutrient recovery, and resource cost of biogas production from household food waste — A comparison of multiple cases from Sweden
- 2022
-
Ingår i: Journal of Cleaner Production. - : Elsevier Science Ltd. - 0959-6526 .- 1879-1786. ; 378
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Tidskriftsartikel (refereegranskat)abstract
- The depletion of natural resources, climate change and energy security are some of today's societal challenges. One way to address these is through anaerobic digestion of food waste, which provides multiple benefits such as waste treatment, nutrient recycling and renewable energy, such as biogas. Biogas solutions tend to vary, so to gain a holistic understanding of their pros and cons there is a need to use a common analytical approach and simultaneously consider several issues. This study has analysed the climate impact, primary energy use, nutrient recycling potential, and resource cost of producing biogas from food waste in three Swedish biogas plants with different setups. In addition, several scenarios representing changes in the existing systems were analysed. The study aims to provide insights into factors that affect the performance of biogas production from food waste. The method applied is based on life cycle analysis and key performance indicators (KPIs), which were used to compare and analyse the performance of the biogas systems. The analysis synthesises a large amount of information about the performance of these systems and their sub-systems. Despite significant differences between the studied cases, all led to the production of biomethane with a low climate impact (62–80% less climate impact in grCO2eq/MJ compared with the fossil reference), low non-renewable primary energy use (16–31% MJ per MJ delivered biomethane), and significant nutrient recovery (e.g., 52–86% of phosphorus content of food waste was delivered as biofertilizer). In addition to the collection system, the efficiency of pretreatment, the choice of energy system (e.g., for heating the biogas plant), and a suitable digestate treatment were found to be among the main factors that influence the overall performance of these systems.
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| 5. |
- Moestedt, Jan, et al.
(författare)
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Acetate and Lactate Production During Two-Stage Anaerobic Digestion of Food Waste Driven by Lactobacillus and Aeriscardovia
- 2020
-
Ingår i: Frontiers in Energy Research. - : FRONTIERS MEDIA SA. - 2296-598X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: In a previous study, single-stage processes were compared with two-stage processes, using either food waste alone or mixed with thin stillage as substrate. Overall methane yield increased (by 12%) in two-stage compared with single-stage digestion when using food waste, but decreased when food waste was co-digested with thin stillage (50:50 on VS basis). The obtained difference in methane yield was likely caused by a higher acetate level in the first stage reactor operating with food waste alone (around 20 g/L) compared to the reactor also treating thin stillage (around 8 g /L). The present study sought to shed additional light on possible causes of the large difference in methane yield by scrutinizing the microbial community in the first- and second-stage reactors, using a combined Illumina sequencing and qPCR approach. Results: In the first-stage process, acid-tolerant Aeriscardovia and Lactobacillus formed a highly efficient consortium. For food waste with high levels of acetate (20 g/L, equal to 0.14 g acetate/g VS) was produced but when thin stillage was added the pH was lower (<4), resulting in lactate production exceeding acetate production. This difference in hydrolysate composition between the reactors resulted in development of slightly different communities in the second-stage, for both hydrolysis, fermentation, and acetogenesis. High acetate concentration appeared to promote proliferation of different syntrophic consortia, such as various syntrophic acetate oxidizers, members of the genus Syntrophomonas and candidate phylum Cloacimonetes, likely explaining the higher methane yields with two-step compared with single-stage digestion of food waste. Conclusion: Using food waste as sole substrate resulted in enrichment of Lactobacillus and Aeriscardovia and high acetate yields in the first-stage reactor. This was beneficial for biogas yield in two-stage digestion, where efficient acid-degrading syntrophic consortia developed. Addition of thin stillage contributed to low pH and higher lactate production, which resulted in decreased methane yield in the two-stage process compared with using food waste as sole substrate.
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| 6. |
- Moestedt, Jan, et al.
(författare)
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Ammonia threshold for inhibition of anaerobic digestion of thin stillage and the importance of organic loading rate
- 2016
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Ingår i: Microbial Biotechnology. - : Wiley. - 1751-7915. ; 9, s. 180-194
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Tidskriftsartikel (refereegranskat)abstract
- Biogas production from nitrogen-rich feedstock results in release of ammonia (NH3), causing inhibition of the microbial process. The reported threshold ammonia value for stable biogas production varies greatly between studies, probably because of differences in operating conditions. Moreover, it is often difficult to separate the effect of ammonia inhibition from that of organic loading rate (OLR), as these two factors are often interrelated. This study attempted to distinguish the effects of ammonia and OLR by analysis of two laboratory-scale biogas reactors operating with thin stillage and subjected to an increase in free ammonia (from 0.30 to 1.1gL(-1)) either by addition of an external nitrogen source (urea) or by increasing the OLR (3.2-6.0g volatile solidsL(-1)d(-1)). The results showed that ammonia concentration was detrimental for process performance, with the threshold for stability in both processes identified as being about 1g NH3-NL-1, irrespective of OLR. Analysis of the methanogenic community showed limited differences between the two reactors on order level and a clear increase in the abundance of Methanomicrobiales, particularly Methanoculleus sp., in response to increasing ammonia concentration. Further comprehensive molecular analysis revealed that diverse Methanoculleus species dominated in the reactors at a given ammonia level at different OLR. The acetogenic community was clearly affected by both ammonia concentration and OLR, suggesting that the volatile fatty acid load in relation to the higher OLR was important for the dynamics of this community.
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| 7. |
- Moestedt, Jan
(författare)
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Biogas production from thin stillage : exploring the microbial response to sulphate and ammonia
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The biogas plant in Norrköping (Tekniska verken i Linköping AB, publ.), Sweden, operates with thin stillage, a residue from bio-ethanol fermentation, as the main feedstock. Thin stillage is energy-rich due to its high protein content, but due to its high nitrogen and sulphate content is a somewhat complicated feedstock. The high nitrogen concentration results in inhibition of the microbial process and also selects for nitrogen-tolerant, but slow-growing, syntrophic acetate-oxidising bacteria (SAOB). The high sulphate concentration in the feedstock results in production of toxic and inhibitory sulphides through the activity of sulphate-reducing bacteria (SRB). Measures currently applied at Norrköping biogas plant to optimise the degradation of thin stillage include: i) use of mesophilic temperature and addition of hydrochloric acid, ii) use of long hydraulic retention time and iii) addition of iron and trace elements. This thesis investigated how to obtain a more efficient biogas process treating thin stillage, with Norrköping biogas plant as the model plant. It also explored the role of SRB in the anaerobic process at high nitrogen content and sought to identify optimal conditions for ammonia-tolerant methane-producing microorganisms. This was done by measuring SRB abundance in several large-scale biogas processes to identify conditions resulting in reduced numbers. In parallel, the effects of increasing temperature and organic load, calcium addition and a two-stage strategy were evaluated in laboratory studies. The results showed a correlation between high ammonia level and temperature with decreased abundance of SRB, but none of the operating strategies tested proved successful in repressing sulphate reduction. However, increasing ammonia and/or organic loading rate influenced both the acetogenic and methanogenic community, including potential SAOB. Moreover, increasing the temperature to 44 ºC resulted in increased abundance of thermotolerant SAOB and their partner methanogen and higher biogas yield (+22%). A maximum ammonia threshold concentration of approximately 1.1 g L-1 was identified. Application of the findings reported in this thesis has resulted in increased process stability in biogas plants in Sweden.
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| 8. |
- Moestedt, Jan, et al.
(författare)
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Biogas Production from Thin Stillage on an Industrial Scale-Experience and Optimisation
- 2013
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 6, s. 5642-5655
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing demand for renewable energy and sustainable waste treatment, biogas production is expanding. Approximately four billion litres of bio-ethanol are produced annually for vehicle fuel in Europe, resulting in the production of large amounts of stillage residues. This stillage is energy-rich and can be used for biogas production, but is a challenging substrate due to its high levels of nitrogen and sulphate. At the full-scale biogas production plant in Norrkoping, Sweden (Svensk Biogas i Linkoping AB), thin grain stillage is used as a biogas substrate. This paper describes the plant operation and strategies that have been implemented to digest thin stillage successfully. High ammonia concentrations in the digester have resulted in syntrophic acetate oxidation (SAO) becoming the major pathway for acetate degradation. Therefore, a long hydraulic retention time (HRT) (40-60 days) is used to allow the syntrophic acetate-oxidising bacteria time to grow. The high sulphate levels in thin stillage result in high levels of hydrogen sulphide following degradation of protein and the activity of sulphate-reducing bacteria (SRB), the presence of which has been confirmed by quantitative polymerase chain reaction (qPCR) analysis. To optimise biogas production and maintain a stable process, the substrate is diluted with tap water and co-digested with grain residues and glycerine to keep the ammonium nitrogen (NH4-N) concentration below 6 g L-1. Combined addition of iron, hydrochloric acid and cobalt successfully precipitates sulphides, reduces ammonia toxicity and supplies microorganisms with trace element. Mesophilic temperature (38 degrees C) is employed to further avoid ammonia toxicity. Together, these measures and doubling the digester volume have made it possible to increase annual biogas production from 27.7 TJ to 69.1 TJ.
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| 9. |
- Moestedt, Jan
(författare)
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Co-digestion of manure and industrial waste - The effects of trace element addition
- 2016
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X. ; 47, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Manure is one of the most common substrates for biogas production. Manure from dairy-and swine animals are often considered to stabilize the biogas process by contributing nutrients and trace elements needed for the biogas process. In this study two lab-scale reactors were used to evaluate the effects of trace element addition during co-digestion of manure from swine-and dairy animals with industrial waste. The substrate used contained high background concentrations of both cobalt and nickel, which are considered to be the most important trace elements. In the reactor receiving additional trace elements, the volatile fatty acids (VFA) concentration was 89% lower than in the control reactor. The lower VFA concentration contributed to a more digested digestate, and thus lower methane emissions in the subsequent storage. Also, the biogas production rate increased with 24% and the biogas production yield with 10%, both as a result of the additional trace elements at high organic loading rates. All in all, even though 50% of the feedstock consisted of manure, trace element addition resulted in multiple positive effects and a more reliable process with stable and high yield.(c) 2015 Elsevier Ltd. All rights reserved.
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| 10. |
- Moestedt, Jan, et al.
(författare)
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Comparison of operating strategies for increased biogas production from thin stillage
- 2014
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 175, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- The effect of increasing organic loading rate (OLR) and simultaneously decreasing hydraulic retentiontime (HRT) during anaerobic digestion of sulphur-and nitrogen-rich thin stillage was investigated duringoperation of continuously stirred tank laboratory reactors at two different temperatures. The operatingstrategies and substrate were set in order to mimic an existing full-scale commercial biogas plant inSweden. The reactors were operated for 554-570 days with a substrate mixture of thin stillage andmilled grain, resulting in high ammonium concentrations (> 4.5 g L-1). Initially, one reactor was operatedat 38. C, as in the full-scale plant, while in the experimental reactor the temperature was raised to 44. C. Both reactors were then subjected to increasing OLR (from 3.2 to 6.0 g VS L-1d-1) and simultaneouslydecreasing HRT (from 45 to 24 days) to evaluate the effects of these operational strategies on processstability, hydrogen sulphide levels and microbial composition. The results showed that operation at44. C was the most successful strategy, resulting in up to 22% higher methane yield compared with themesophilic reactor, despite higher free ammonia concentration. Furthermore, kinetic studies revealedhigher biogas production rate at 44. C compared with 38. C, while the level of hydrogen sulphide wasnot affected. Quantitative PCR analysis of the microbiological population showed that methanogenicarchaea and syntrophic acetate-oxidising bacteria had responded to the new process temperature whilesulphatereducing bacteria were only marginally affected by the temperature-change. (C) 2014 Elsevier B. V. All rights reserved.
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| 11. |
- Moestedt, Jan
(författare)
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Determination of Methane and Carbon Dioxide Formation Rate Constants for Semi-Continuously Fed Anaerobic Digesters
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8, s. 645-655
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Tidskriftsartikel (refereegranskat)abstract
- To optimize commercial-scale biogas production, it is important to evaluate the performance of each microbial step in the anaerobic process. Hydrolysis and methanogenesis are usually the rate-limiting steps during digestion of organic waste and by-products. By measuring biogas production and methane concentrations on-line in a semi-continuously fed reactor, gas kinetics can be evaluated. In this study, the rate constants of the fermentative hydrolysis step (k(c)) and the methanogenesis step (k(m)) were determined and evaluated in a continuously stirred tank laboratory-scale reactor treating food and slaughterhouse waste and glycerin. A process additive containing Fe2+, Co2+ and Ni2+ was supplied until day 89, after which Ni2+ was omitted. The omission resulted in a rapid decline in the methanogenesis rate constant (k(m)) to 70% of the level observed when Ni2+ was present, while kc remained unaffected. This suggests that Ni2+ mainly affects the methanogenic rather than the hydrolytic microorganisms in the system. However, no effect was initially observed when using conventional process monitoring parameters such as biogas yield and volatile fatty acid concentration. Hence, formation rate constants can reveal additional information on process performance and km can be used as a complement to conventional process monitoring tools for semi-continuously fed anaerobic digesters.
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| 12. |
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| 13. |
- Moestedt, Jan, et al.
(författare)
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Effects of trace element addition on process stability during anaerobic co-digestion of OFMSW and slaughterhouse waste
- 2016
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Ingår i: Waste Management. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0956-053X .- 1879-2456. ; 47:Pt A, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- This study used semi-continuous laboratory scale biogas reactors to simulate the effects of trace-element addition in different combinations, while degrading the organic fraction of municipal solid waste and slaughterhouse waste. The results show that the combined addition of Fe, Co and Ni was superior to the addition of only Fe, Fe and Co or Fe and Ni. However, the addition of only Fe resulted in a more stable process than the combined addition of Fe and Co, perhaps indicating a too efficient acidogenesis and/or homoacetogenesis in relation to a Ni-deprived methanogenic population. The results were observed in terms of higher biogas production (+9%), biogas production rates (+35%) and reduced VFA concentration for combined addition compared to only Fe and Ni. The higher stability was supported by observations of differences in viscosity, intraday WA-and biogas kinetics as well as by the 16S rRNA gene and 16S rRNA of the methanogens.(c) 2015 Elsevier Ltd. All rights reserved.
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| 14. |
- Moestedt, Jan, et al.
(författare)
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Inoculum Source Determines Acetate and Lactate Production during Anaerobic Digestion of Sewage Sludge and Food Waste
- 2020
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Ingår i: Bioengineering. - : MDPI AG. - 2306-5354. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Acetate production from food waste or sewage sludge was evaluated in four semi-continuous anaerobic digestion processes. To examine the importance of inoculum and substrate for acid production, two different inoculum sources (a wastewater treatment plant (WWTP) and a co-digestion plant treating food and industry waste) and two common substrates (sewage sludge and food waste) were used in process operations. The processes were evaluated with regard to the efficiency of hydrolysis, acidogenesis, acetogenesis, and methanogenesis and the microbial community structure was determined. Feeding sewage sludge led to mixed acid fermentation and low total acid yield, whereas feeding food waste resulted in the production of high acetate and lactate yields. Inoculum from WWTP with sewage sludge substrate resulted in maintained methane production, despite a low hydraulic retention time. For food waste, the process using inoculum from WWTP produced high levels of lactate (30 g/L) and acetate (10 g/L), while the process initiated with inoculum from the co-digestion plant had higher acetate (25 g/L) and lower lactate (15 g/L) levels. The microbial communities developed during acid production consisted of the major genera Lactobacillus (92-100%) with food waste substrate, and Roseburia (44-45%) and Fastidiosipila (16-36%) with sewage sludge substrate. Use of the outgoing material (hydrolysates) in a biogas production system resulted in a non-significant increase in bio-methane production (+5-20%) compared with direct biogas production from food waste and sewage sludge.
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| 15. |
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| 16. |
- Moestedt, Jan, et al.
(författare)
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The effect of substrate and operational parameters on the abundance of sulphate-reducing bacteria in industrial anaerobic biogas digesters
- 2013
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 132, s. 327-332
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the effects of operational parameters and type of substrate on the abundance of sulphate-reducing bacteria in 25 industrial biogas digesters using qPCR targeting the functional dissimilatory sulphite reductase gene. The aim was to find clues for operational strategies minimizing the production of H2S. The results showed that the operation, considering strategies evaluated, only had scarce effect on the abundance, varying between 10(5) and 10(7) gene copies per ml. However, high ammonia levels and increasing concentration of sulphate resulted in significantly lower and higher levels of sulphate-reducing bacteria, respectively. (C) 2013 Elsevier Ltd. All rights reserved.
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| 17. |
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| 18. |
- Nilsson Påledal, Sören, et al.
(författare)
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Characterisation and treatment of VOCs in process water from upgrading facilities for compressed biogas (CBG)
- 2016
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 145, s. 424-430
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Tidskriftsartikel (refereegranskat)abstract
- Compression and upgrading of biogas to vehicle fuel generates process water, which to varying degrees contains volatile organic compounds (VOCs) originating from the biogas. The compostion of this process water has not yet been studied and scientifically published and there is currently an uncertainty regarding content of VOCs and how the process water should be managed to minimise the impact on health and the environment. The aim of the study was to give an overview about general levels of VOCs in the process water. Characterisation of process water from amine and water scrubbers at plants digesting waste, sewage sludge or agricultural residues showed that both the average concentration and composition of particular VOCs varied depending on the substrate used at the biogas plant, but the divergence was high and the differences for total concentrations from the different substrate groups were only significant for samples from plants using waste compared to residues from agriculture. The characterisation also showed that the content of VOCs varied greatly between different sampling points for same main substrate and between sampling occasions at the same sampling point, indicating that site-specific conditions are important for the results which also indicates that a number of analyses at different times are required in order to make an more exact characterisation with low uncertainty.Inhibition of VOCs in the anaerobic digestion (AD) process was studied in biomethane potential tests, but no inhibition was observed during addition of synthetic process water at concentrations of 11.6 mg and 238 mg VOC/L.
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| 19. |
- Nordell, Erik, et al.
(författare)
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Post-treatment of dewatered digested sewage sludge by thermophilic high-solid digestion for pasteurization with positive energy output
- 2021
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 119, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the possibility to use thermophilic anaerobic high solid digestion of dewatered digested sewage sludge (DDS) at a wastewater treatment plant (WWTP) as a measure to increase total methane yield, achieve pasteurization and reduce risk for methane emissions during storage of the digestate. A pilot-scale plug-flow reactor was used to mimic thermophilic post-treatment of DDS from a WWTP in Linköping, Sweden. Process operation was evaluated with respect to biogas process performance, using both chemical and microbiological parameters. Initially, the process showed disturbance, with low methane yields and high volatile fatty acid (VFA) accumulation. However, after initiation of digestate recirculation performance improved and the specific methane production reached 46 mL CH4/g VS. Plug flow conditions were assessed with lithium chloride and the hydraulic retention time (HRT) was determined to be 19–29 days, sufficient to reach successful pasteurization. Degradation rate of raw protein was high and resulted in ammonia-nitrogen levels of up to 2.0 g/L and a 30% lower protein content in the digestate as compared to DDS. Microbial analysis suggested a shift in the methane producing pathway, with dominance of syntrophic acetate oxidation and the candidate methanogen family WSA2 by the end of the experiment. Energy balance calculations based on annual DDS production of 10 000 ton/year showed that introduction of high-solid digestion as a post-treatment and pasteurization method would result in a positive energy output of 340 MWh/year. Post-digestion of DDS also decreased residual methane potential (RMP) by>96% compared with fresh DDS.
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| 20. |
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| 21. |
- Nordell, Erik, et al.
(författare)
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Thermal post-treatment of digestate in order to increase biogas production with simultaneous pasteurization
- 2022
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Ingår i: Journal of Biotechnology. - : Elsevier. - 0168-1656 .- 1873-4863. ; :344, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- Biogas production by anaerobic digestion (AD) of organic wastes is important for the transition to fossil free fuelsin both the transport sector, industries and shipping. The aim of this study was to target the residual organicmatter in the outgoing residue from the AD process, so called digestate, with different thermal treatmentmethods in order to improve digestate degradability and biogas potential upon post-digestion. The thermaltreatment was performed at 55 ◦C in 24 h, 70 ◦C in 1 h and by thermal hydrolysis process (THP; 165 ◦C, 8 bar in0.33 h), and were carefully selected to offer a simultaneous possibility for pasteurization of the digestate accordingto the regulations in Sweden. Digestates from ten full-scale biogas plants were collected, with differentsubstrate profiles including wastewater treatment plant (WWTP), food waste digestion, agriculture digestion andmanure digestion. The results showed that all thermal treatment methods caused increased dissolved organiccarbon concentration (DOC). Four of the thermal treated digestates with the highest increase in DOC weresubsequently tested for the bio-methane potential. Thermal treatments at 70 ◦C and THP, respectively, resulted inthe highest increase in bio-methane potentials, with an increase of 15–39% for one WWTP, 38 – 40% fordigestate from an agriculture digestion plant and 20 – 22% for digestate from a co-digestion plant treating foodwaste. Interestingly, the bio-methane potential from digestate treated with the energy-intense THP method, didnot show any significant difference compared to thermal treatment at 70 ◦C for 1 h. The outcomes of this studysuggest that placing a pasteurization unit between a main digester and a post digester, when applying two-stepdigestion allows for a combined pasteurization and increased biogas production.
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| 22. |
- Perman, Ebba, et al.
(författare)
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Serial anaerobic digestion improves protein degradation and biogas production from mixed food waste
- 2022
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Ingår i: Biomass and Bioenergy. - Oxford, United Kingdom : Elsevier. - 0961-9534 .- 1873-2909. ; 161
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of the biogas generation process is important to achieve efficient degradation and high methane yield, and to reduce methane emissions from the digestate. In this study, serial digester systems with two or three biogas reactors were compared with a single reactor, with the aim of improving degree of degradation and methane yield from food waste and assessing adaptation of microbial communities to different reactor steps. All systems had the same total organic load (2.4 g VS/(L d)) and hydraulic retention time (55 days). Serial systems increased methane yield by >5% compared with the single reactor, with the majority of the methane being obtained from the first-step reactors. Improved protein degradation was also obtained in serial systems, with >20% lower outgoing protein concentration compared with the single reactor and increasing NH4+-N concentration with every reactor step. This resulted in separation of high ammonia (>384 mg NH3-N/L) levels from the main methane production, reducing the risk of methanogen inhibition. Methanosarcina dominated the methanogenic community in all reactors, but increases in the hydrogenotrophic genera Methanoculleus and Methanobacterium were observed at higher ammonia levels. Potential syntrophic acetate-oxidizing bacteria, such as MBA03 and Dethiobacteraceae, followed the same trend as the hydrogenotrophic methanogens. Phylum Bacteroidota family Paludibacteraceae was highly abundant in the first steps and then decreased abruptly, potentially linked to an observed decrease in degradation in the last-step reactors. Nevertheless, the results indicated a trend of increasing relative abundance of the potentially proteolytic genera Proteiniphilum and Fastidiosipila with successive reactor steps.
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| 23. |
- Pinela, Eduardo, et al.
(författare)
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Impact of additives on syntrophic propionate and acetate enrichments under high-ammonia conditions
- 2024
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Ingår i: Applied Microbiology and Biotechnology. - : SPRINGER. - 0175-7598 .- 1432-0614. ; 108:1
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Tidskriftsartikel (refereegranskat)abstract
- High ammonia concentrations in anaerobic degradation systems cause volatile fatty acid accumulation and reduced methane yield, which often derive from restricted activity of syntrophic acid-oxidising bacteria and hydrogenotrophic methanogens. Inclusion of additives that facilitate the electron transfer or increase cell proximity of syntrophic species by flocculation can be a suitable strategy to counteract these problems, but its actual impact on syntrophic interactions has yet to be determined. In this study, microbial cultivation and molecular and microscopic analysis were performed to evaluate the impact of conductive (graphene, iron oxide) and non-conductive (zeolite) additives on the degradation rate of acetate and propionate to methane by highly enriched ammonia-tolerant syntrophic cultures derived from a biogas process. All additives had a low impact on the lag phase but resulted in a higher rate of acetate (except graphene) and propionate degradation. The syntrophic bacteria 'Candidatus Syntrophopropionicum ammoniitolerans', Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen were found in higher relative abundance and higher gene copy numbers in flocculating communities than in planktonic communities in the cultures, indicating benefits to syntrophs of living in close proximity to their cooperating partner. Microscopy and element analysis showed precipitation of phosphates and biofilm formation in all batches except on the graphene batches, possibly enhancing the rate of acetate and propionate degradation. Overall, the concordance of responses observed in both acetate- and propionate-fed cultures highlight the suitability of the addition of iron oxide or zeolites to enhance acid conversion to methane in high-ammonia biogas processes.
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| 24. |
- Schnürer, Anna, et al.
(författare)
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Protocol for start-up and operation of CSTR biogas processes
- 2017
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Ingår i: Hydrocarbon and Lipid Microbiology Protocols : Bioproducts, Biofuels, Biocatalysts and Facilitating Tools. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783662531136 ; , s. 171-200
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Bokkapitel (refereegranskat)
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| 25. |
- Singh, Abhijeet, et al.
(författare)
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Microbiological Surveillance of Biogas Plants: Targeting Acetogenic Community
- 2021
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Acetogens play a very important role in anaerobic digestion and are essential in ensuring process stability. Despite this, targeted studies of the acetogenic community in biogas processes remain limited. Some efforts have been made to identify and understand this community, but the lack of a reliable molecular analysis strategy makes the detection of acetogenic bacteria tedious. Recent studies suggest that screening of bacterial genetic material for formyltetrahydrofolate synthetase (FTHFS), a key marker enzyme in the Wood-Ljungdahl pathway, can give a strong indication of the presence of putative acetogens in biogas environments. In this study, we applied an acetogen-targeted analyses strategy developed previously by our research group for microbiological surveillance of commercial biogas plants. The surveillance comprised high-throughput sequencing of FTHFS gene amplicons and unsupervised data analysis with the AcetoScan pipeline. The results showed differences in the acetogenic community structure related to feed substrate and operating parameters. They also indicated that our surveillance method can be helpful in the detection of community changes before observed changes in physico-chemical profiles, and that frequent high-throughput surveillance can assist in management towards stable process operation, thus improving the economic viability of biogas plants. To our knowledge, this is the first study to apply a high-throughput microbiological surveillance approach to visualise the potential acetogenic population in commercial biogas digesters.
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| 26. |
- Westerholm, Maria, et al.
(författare)
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Biogas production through syntrophic acetate oxidation and deliberate operating strategies for improved digester performance
- 2016
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 179, s. 124-135
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic degradation of protein-rich materials has high methane potential and produces nutrient-rich residue, but requires strategies to avoid ammonia inhibition. A well-adapted process can cope with substantially higher ammonia levels than an unadapted process and analyses of pathways for methanisation of acetate, combined with determination of microbial community structure, strongly indicate that this is due to a significant contribution of syntrophic acetate oxidation. The microorganisms involved in syntrophic acetate oxidation thus most likely occupy a unique niche and play an important role in methane formation. This review summarises current insight of syntrophic acetate oxidising microorganisms, their presence and the detection of novel species and relate these observations with operating conditions of the biogas processes in order to explore contributing factors for development of an ammonia-tolerant microbial community that efficiently degrades acetate through the syntrophic pathway. Besides high ammonia level, acetate concentration, temperature and methanogenic community structure are considered in this review as likely factors that shape and influence SAO-mediated microbial ecosystems. The main purpose of this review is to facilitate process optimisation through considering the activity and growth of this key microbial community. (C) 2016 The Authors. Published by Elsevier Ltd.
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