| 1. |
- Anacleto, Thuane Mendes, et al.
(författare)
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Methane yield response to pretreatment is dependent on substrate chemical composition: a meta-analysis on anaerobic digestion systems
- 2024
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Ingår i: Scientific Reports. - : NATURE PORTFOLIO. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Proper pretreatment of organic residues prior to anaerobic digestion (AD) can maximize global biogas production from varying sources without increasing the amount of digestate, contributing to global decarbonization goals. However, the efficiency of pretreatments applied on varying organic streams is poorly assessed. Thus, we performed a meta-analysis on AD studies to evaluate the efficiencies of pretreatments with respect to biogas production measured as methane yield. Based on 1374 observations our analysis shows that pretreatment efficiency is dependent on substrate chemical dominance. Grouping substrates by chemical composition e.g., lignocellulosic-, protein- and lipid-rich dominance helps to highlight the appropriate choice of pretreatment that supports maximum substrate degradation and more efficient conversion to biogas. Methane yield can undergo an impactful increase compared to untreated controls if proper pretreatment of substrates of a given chemical dominance is applied. Non-significant or even adverse effects on AD are, however, observed when the substrate chemical dominance is disregarded.
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| 2. |
- 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. - 2589-014X. ; 27, s. 101887-101887
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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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| 3. |
- Babatunde Adeleke, Solomon, et al.
(författare)
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Geochemical control processes and potential sediment toxicity in a mine-impacted lake
- 2016
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Ingår i: Environmental Toxicology and Chemistry. - : WILEY-BLACKWELL. - 0730-7268 .- 1552-8618. ; 35:3, s. 563-572
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Tidskriftsartikel (refereegranskat)abstract
- Geochemical parameters and major ion concentrations from sediments of a freshwater lake in the town of angstrom tvidaberg, southeastern, Sweden, were used to identify the geochemical processes that control the water chemistry. The lake sediments are anoxic, characterized by reduced sulfur and sulfidic minerals. The hypothesis tested is that in sulfidic-anaerobic contaminated sediments, the presence of redox potential changes creates a favorable condition for sulfide oxidation, resulting in the release of potentially toxic metals. The acid volatile sulfide (AVS) contents ranged from 5.5mol/g to 16mol/g of dry sediment. Comparison of total mine tailing metals (Sigma mine tailing metals) with simultaneously extracted metals (SEM) in sediments indicates that up to 20% of the Sigma mine tailing metals are bound to the solid phase as AVS. Consequently, the AVS and SEM analysis classified all sediment samples as potentially toxic in terms of heavy metal concentrations (i.e., SEM to AVS ratio distribution>1). Evaluation of hydrogeochemical data suggests that calcite dissolution, iron (III) oxyhydroxysulfate mineral jarosite (H-jarosite) precipitation, hematite precipitation, and siderite precipitation are the most prevailing geochemical processes that control the geochemical interactions between the water column and sediment in a mine-impacted lake. The geochemical processes were verified and quantified using a chemical equilibrium modeling program, Visual MINTEQ, Ver 3.1, beta. The identified geochemical processes create an environment in which the characteristics of sulfate-rich waters and acidic-iron produce the geochemical conditions for acid mine drainage and mobilization of toxic metals. (c) 2015 SETAC
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| 4. |
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| 5. |
- Björn, Annika, 1972-, et al.
(författare)
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Rheological characteristics of reactor liquid from 12 full-scale biogas reactors
- 2012
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Ingår i: International Conference on Applied Energy, ICAE 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Rheological properties of reactor liquids are important for the construction and intensity mixing systems in biogas reactors. Most frequently the total solids content (TS) is used as a proxy to guide in these matters. In order to establish a more comprehensive basis the rheology of twelve full-scale continuously stirred tank biogas reactors was characterized and related to differences in substrate composition and operational conditions. Reactor material from eight mesophilic (36−38°C) and four thermophilic (52−55°C) reactors were sampled at two occasions. The feedstocks of nine of these reactors were included in the analysis. Two of the mesophilic and one of the thermophilic digesters were fed sewage sludge (SS), while the others digested mixtures of organic matter including slaughterhouse waste (SHW), food industry waste (FIW), fat, manure, fodder residues and the organic fraction of municipal solid waste (OFMSW). The organic loading rates ranged 2.4−3.6 kg VS m-3 d-1 and the TS of the reactor materials were at 1.8−5.3% . The rheological characteristics of the reactor liquids were interpreted from flow- and viscosity curves as well as from determination of dynamic viscosity, limit viscosity, yield stress, flow behavior and consistency index.The fluid dynamic- and limit viscosities of the fluids ranged 5−600 mPa*s and 4−40 mPa*s, respectively. All reactor fluids except one from a thermohilic CD-reactor showed pseudoplastic behavior, since they became thinner with increasing shear stress until the viscosity reached a plateau of limit viscosity. In addition the mesophilic CD reactors were strongly thixothropic, i.e. they exhibited partial structure recovery. The results from the analysis of the thermophilic CD-reactors indicated a weak dilatant behavior, i.e. shear thickening behavior.The results showed differences in viscosity despite similar TS-content for several reactor liquids. From this survey it is clear that the TS content of biogas reactor fluids is not a good estimator of the fluid viscosity and that the fluid characteristics vary as a result of substrate composition and process operation conditions.
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| 6. |
- Björn, Annika, et al.
(författare)
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Substrate and operational conditions as regulators of fluid properties in full-scale continuous stirred-tank biogas reactors - implications for rheology-driven power requirements
- 2018
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Ingår i: Water Science and Technology. - : IWA PUBLISHING. - 0273-1223 .- 1996-9732. ; 78:4, s. 814-826
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Tidskriftsartikel (refereegranskat)abstract
- Understanding fluid rheology is important for optimal design and operation of continuous stirred-tank biogas reactors (CSTBRs) and is the basis for power requirement estimates. Conflicting results have been reported regarding the applicability of total solid (TS) and/or total volatile solid (TVS) contents of CSTBR fluids as proxies for rheological properties. Thus, the present study investigates relationships between rheological properties of 12 full-scale CSTBR fluids, their substrate profiles, and major operational conditions, including pH, TS and TVS contents, organic loading rate, hydraulic retention time, and temperature. Rheology-driven power requirements based on various fluid characteristics were evaluated for a general biogas reactor setup. The results revealed a significant correlation only between the rheological fluid properties and TS or TVS contents for sewage sludge digesters and thermophilic co-digesters (CD), but not for mesophilic CD. Furthermore, the calculated power requirements for pumping and mixing, based on the various fluid characteristics of the studied CSTBRs, varied broadly irrespective of TS and TVS contents. Thus, this study shows that the TS and/or TVS contents of digester fluid are not reliable estimators of the rheological properties in CSTBRs digesting substrates other than sewage sludge.
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| 7. |
- Björn (Fredriksson), Annika, 1972-, et al.
(författare)
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Feasibility of OFMSW co-digestion with sewage sludge for increasing biogas production at wastewater treatment plants
- 2017
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Ingår i: Euro-Mediterranean Journal for Environmental Integration. - : Springer. - 2365-6433 .- 2365-7448. ; 2:21
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has the ambition to increase its annual biogas production from the current level of 1.9 to 15 TWh by 2030. The unused capacity of existing anaerobic digesters at wastewater treatment plants is among the options to accomplish this goal. This study investigated the feasibility of utilizing the organic fraction of municipal solid waste (OFMSW) as a co-substrate, with primary and waste-activated sewage sludge (PWASS) for production of biogas, corresponding to 3:1 ratio on volatile solid (VS) basis. The results demonstrated that co-digestion of OFMSW with PWASS at an organic loading rate of 5 gVS l−1 day−1 has the potential to increase the biogas production approximately four times. The daily biogas production increased from 1.0 ± 0.1 to 3.8 ± 0.3 l biogasl−1 day−1, corresponding to a specific methane production of 420 ± 30 Nml methane gVS−1 during the laboratory experiment. Co-digestion of OFMSW with PWASS showed a 50:50 distribution of hydrogenotrophic and aceticlastic methanogens in the digester and enhanced the turnover kinetics of intermediate products (acetate, propionate, and oleate). Practical limitations potentially include the need for sludge dewatering to maintain a sufficient hydraulic retention time (17 days in this study), as well as additional energy consumption for mixing due to an increased sludge apparent viscosity (from 1.8 ± 0.1 to 45 ± 4.8 mPa*s in this study) at elevated OFMSW-loading rates.
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| 8. |
- Bonaglia, Stefano, et al.
(författare)
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Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter Research. - 0171-8630 .- 1616-1599. ; 482, s. 43-55
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient reduction and the improvement of bottom water oxygen concentrations are thought to be key factors in the recovery of eutrophic aquatic ecosystems. The effects of reoxygenation and bioturbation of natural hypoxic sediments in the Baltic Sea were studied using a mesocosm experiment. Anoxic sediment box cores were collected from 100 m depth in Kanholmsfjärden (Stockholm Archipelago) and maintained in flow-through mesocosms with 3 treatments: (1) hypoxic: supplied with hypoxic water; (2) normoxic: supplied with oxic water; and (3) Marenzelleria: supplied with oxic water and the polychaete Marenzelleria spp. (2000 ind. m–2). After a 7 wk long conditioning period, net fluxes of dissolved O2, CH4, Fe2+, Mn2+, NH4+, NO2-, NO3-, PO43- and H4SiO4, and rates of nitrate ammonification (DNRA), denitrification and anammox were determined. Phosphate was taken up by the sediment in all treatments, and the uptake was highest in the normoxic treatment with Marenzelleria. Normoxic conditions stimulated the denitrification rate by a factor of 5. Denitrification efficiency was highest under normoxia (50%), intermediate in bioturbated sediments (16%), and very low in hypoxic sediments (4%). The shift from hypoxic to normoxic conditions resulted in a significantly higher retention of NH4+, H4SiO4 and Mn2+ in the sediment, but the bioturbation by Marenzelleria reversed this effect. Results from our study suggest that bioturbation by Marenzelleria stimulates the exchange of solutes between sediment and bottom water through irrigation and enhances bacterial sulfate reduction in the burrow walls. The latter may have a toxic effect on nitrifying bacteria, which, in turn, suppresses denitrification rates.
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