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Karlsson A.,Linköping University | Truong X.-B.,Scandinavian Biogas Fuels AB | Gustavsson J.,Linköping University | Svensson B.H.,Linköping University | And 2 more authors.
Environmental Technology | Year: 2011

The methane potential of activated sludge from six Swedish pulp and paper mills was evaluated. The methane production potential of sludge samples ranged from 100-200 NmL CH4 g-1 volatile solids (VS) and for four of the six sludge samples the potential exceeded 170 NmL CH4 g -1 VS. The effects of sludge age and dewatering on the methane production potential were evaluated. The effects of enzymatic and ultrasonic pre-treatment on the digestibility of sludge were also investigated, but energy or enzyme inputs in viable ranges did not exert a detectable, positive effect. Long-term, semi-continuous trials with sludge from two of the mills were also conducted in attempts to develop stable biogas production at loading rates up to 4 g VS L-1 . Cobalt addition (0.5 mg L-1 ) was here found to positively affect the turnover of acetate. High viscosity was a problem in all the experimental reactors and this limited the organic loading rate. © 2011 Taylor & Francis.

Karlsson A.,Linköping University | Einarsson P.,Linköping University | Einarsson P.,Scandinavian Biogas Fuels AB | Schnurer A.,Swedish University of Agricultural Sciences | And 4 more authors.
Journal of Bioscience and Bioengineering | Year: 2012

The effect of trace element addition on anaerobic digestion of food industry- and household waste was studied using two semi-continuous lab-scale reactors, one (R30+) was supplied with Fe, Co and Ni, while the other (R30) acted as a control. Tracer analysis illustrated that methane production from acetate proceeded through syntrophic acetate oxidation (SAO) in both digesters. The effect of the trace elements was also evaluated in batch assays to determine the capacity of the microorganisms of the two digesters to degrade acetate, phenyl acetate, oleic acid or propionate, butyrate and valerate provided as a cocktail. The trace elements addition improved the performance of the process giving higher methane yields during start-up and early operation and lower levels of mainly acetate and propionate in the R30+ reactor. The batch assay showed that material from R30+ gave effects on methane production from all substrates tested. Phenyl acetate was observed to inhibit methane formation in the R30 but not in the R30+ assay. A real-time PCR analysis targeting methanogens on the order level as well as three SAO bacteria showed an increase in Methanosarcinales in the R30+ reactor over time, even though SAO continuously was the dominating pathway for methane production. Possibly, this increase explains the low VFA-levels and higher degradation rates observed in the R30+ batch incubations. These results show that the added trace elements affected the ability of the microflora to degrade VFAs as well as oleic acid and phenyl acetate in a community, where acetate utilization is dominated by SAO. © 2012 The Society for Biotechnology, Japan.

Ekstrand E.-M.,Linköping University | Larsson M.,Linköping University | Truong X.-B.,Scandinavian Biogas Fuels AB | Cardell L.,Scandinavian Biogas Fuels AB | And 7 more authors.
Applied Energy | Year: 2013

With the final aim of reducing the energy consumption and increase the methane production at Swedish pulp and paper mills, the methane potential of 62 wastewater effluents from 10 processes at seven pulp and/or paper mills (A-G) was determined in anaerobic batch digestion assays. This mapping is a first step towards an energy efficient and more sustainable utilization of the effluents by anaerobic digestion, and will be followed up by tests in lab-scale and pilot-scale reactors. Five of the mills produce kraft pulp (KP), one thermo-mechanical pulp (TMP), two chemical thermo-mechanical pulp (CTMP) and two neutral sulfite semi-chemical (NSSC) pulp. Both elementary and total chlorine free (ECF and TCF, respectively) bleaching processes were included. The effluents included material from wood rooms, cooking and oxygen delignification, bleaching (often both acid- and alkali effluents), drying and paper/board machinery as well as total effluents before and after sedimentation.The results from the screening showed a large variation in methane yields (percent of theoretical methane potential assuming 940NmL CH4 per g TOC) among the effluents. For the KP-mills, methane yields above 50% were obtained for the cooking effluents from mills D and F, paper machine wastewater from mill D, condensate streams from mills B, E and F and the composite pre-sedimentation effluent from mill D. The acidic ECF-effluents were shown to be the most toxic to the AD-flora and also seemed to have a negative effect on the yields of composite effluents downstream while three of the alkaline ECF-bleaching effluents gave positive methane yields. ECF bleaching streams gave higher methane yields when hardwood was processed. All TCF-bleaching effluents at the KP mills gave similar degradation patterns with final yields of 10-15% of the theoretical methane potential for four of the five effluents. The composite effluents from the two NSSC-processes gave methane yields of 60% of the theoretical potential.The TMP mill (A) gave the best average yield with all six effluents ranging 40-65% of the theoretical potential. The three samples from the CTMP process at mill B showed potentials around 40% while three of the six effluents at mill G (CTMP) yielded 45-50%. © 2013 Elsevier Ltd.

Gustavsson J.,Linköping University | Shakeri Yekta S.,Linköping University | Sundberg C.,Linköping University | Karlsson A.,Scandinavian Biogas Fuels AB | And 4 more authors.
Applied Energy | Year: 2013

Addition of Co and Ni often improves the production of biogas during digestion of organic matter, i.e. increasing CH4-production, process stability and substrate utilization which often opens for higher organic loading rates (OLRs). The effect of Co and Ni addition was evaluated by measuring methane production, volatile solids reduction, pH and concentration of volatile fatty acids (VFAs). A series of six lab.-scale semi-continuously fed biogas tank reactors were used for this purpose. The chemical forms and potential bioavailability of Co and Ni were examined by sequential extraction, acid volatile sulfide extraction (AVS) and simultaneously extracted metals. Furthermore, the sulfur speciation in solid phase was examined by sulfur X-ray absorption near edge structure spectroscopy. The effect of Co and Ni deficiency on the microbial community composition was analyzed using quantitative polymerase chain reaction and 454-pyrosequencing. The results showed that amendment with Co and Ni was necessary to maintain biogas process stability and resulted in increased CH4-production and substrate utilization efficiency. 10-20% of the total Co concentration was in dissolved form and should be regarded as easily accessible by the microorganisms. In contrast, Ni was entirely associated with organic matter/sulfides (mainly AVS) and regarded as very difficult to take up. Still Ni had stimulatory effects suggesting mechanisms such as dissolution of NiS to be involved in the regulation of Ni availability for the microorganisms. The microbial community structure varied in relation to the occurrence of Ni and Co. The acetate-utilizing Methanosarcinales dominated during stable process performance, i.e. when both Co and Ni were supplied, while hydrogenotrophic Methanomicrobiales increased together with VFA concentrations under Co or Ni deficiency. The increase was more pronounced at Co limitation. This study demonstrates that there are good possibilities to improve the performance of biogas processes digesting sulfur-rich substrates by supplementation of Co and Ni. © 2013 Elsevier Ltd.

Gustavsson J.,Linköping University | Yekta S.S.,Linköping University | Karlsson A.,Scandinavian Biogas Fuels AB | Skyllberg U.,Swedish University of Agricultural Sciences | Svensson B.H.,Linköping University
Engineering in Life Sciences | Year: 2013

Several previous studies reported stimulatory effects on biogas process performance after trace metal supplementation. However, the regulation of the bioavailability in relation to chemical speciation, e.g. the role of sulfide is not fully understood. The objective of the present study was to determine the effect of sulfide on chemical speciation and bioavailability of Co and Ni in lab-scale semicontinuous stirred biogas tank reactors treating stillage. The chemical forms and potential bioavailability of Co and Ni were studied by sequential extraction, analysis of acid-volatile sulfide (AVS), and simultaneously extracted metals. The results demonstrated that Ni was completely associated to the organic matter/sulfide fraction and AVS, suggesting low potential bioavailability. Cobalt was predominantly associated to organic matter/sulfide and AVS, but also to more soluble fractions, which are considered to be more bioavailable. Process data showed that both Co and Ni were available for microbial uptake. Although the actual bioavailability of Co could be explained by association to more bioavailable chemical fractions, the complete association of Ni with organic matter/sulfides and AVS implies that Ni was taken up despite its expected low bioavailability. It was concluded that extensive Co- and Ni-sulfide precipitation did not inhibit microbial uptake of Co and Ni in the reactors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Karlsson A.,Linköping University | Ejlertsson J.,Linköping University | Ejlertsson J.,Scandinavian Biogas Fuels AB
Biochemical Engineering Journal | Year: 2012

The effect of pH on the production of biogas during anaerobic digestion of a protein-rich substrate, containing mainly slaughter house waste, was investigated. Four laboratory scale reactors (4L liquid volume) with an organic load of 3.5g volatile solids (VS) L -1 reactor volume day -1, and a hydraulic retention time 24 days were run under mesophilic conditions in semi-continuous mode for 64 days. Two of the reactors were pH-regulated (target pH was 7.6 and 7.8, respectively) by adding HCl, while the other two reactors were operated as controls (pH 8.0). By the end of the experiment the pH-controlled reactors produced 0.6L of methane gVS added -1day -1, while the controls produced 0.4L. The gas produced did in all cases have a CH 4 - content of about 65%. The improvement in process performance in the pH-regulated reactors, compared to the controls, was also reflected in lower final levels of acetate, propionate, isobutyrate and 2-metylbutyrate. The laboratory-scale study showed that lowering the pH by 0.2-0.4 units by adding HCl to the reactors increased the methane yield with about 50%, indicating a considerable increase of the microbial ability to utilise the organic material for biogas production. © 2011 Elsevier B.V.

PubMed | Scandinavian Biogas Fuels AB and Linköping University
Type: | Journal: Waste management (New York, N.Y.) | Year: 2016

Kraft fibre sludge from the pulp and paper industry constitutes a new, widely available substrate for the biogas production industry, with high methane potential. In this study, anaerobic digestion of kraft fibre sludge was examined by applying continuously stirred tank reactors (CSTR) with sludge recirculation. Two lab-scale reactors (4L) were run for 800days, one on fibre sludge (R1), and the other on fibre sludge and activated sludge (R2). Additions of Mg, K and S stabilized reactor performance. Furthermore, the Ca:Mg ratio was important, and a stable process was achieved at a ratio below 16:1. Foaming was abated by short but frequent mixing. Co-digestion of fibre sludge and activated sludge resulted in more robust conditions, and high-rate operation at stable conditions was achieved at an organic loading rate of 4g volatile solids (VS)L(-1)day(-1), a hydraulic retention time of 4days and a methane production of 23010NmL per g VS.

News Article | November 17, 2016

Biogas is a blend of various gases formed by breaking down the organic substances in the absence of oxygen. Wastes from agricultural utilities, municipalities, plants and industries, sewage or edible wastes work as the raw materials for biogas production. Exerting little carbon footprint, Biogas is a renewable energy source, use of which is good for the environment. Biogas can be produced by the following methods: Biogas is mainly composed of methane and carbon dioxide gases. Minor amounts of hydrogen sulphide, water vapours and silicone compounds may also be found in the mixture. The gases present in biogas can be burnt in the presence of oxygen, which releases energy. The energy thus released can be used for various purposes such as cooking food, generating electricity, heating and also in transportation. The global shift in the use of energy from conventional resources to unconventional or renewable energy resources is expected to be the main factor driving the global biogas market. Various governmental and environmental regulations and legislations in the favour of biogas are also playing a governing role in the global biogas market. Owing to these factors, the global biogas market is expected to grow significantly over the forecast period of 2016-2026. Increasing prices of conventional energy resources such as crude oil etc. over the years, have helped to stimulate the global interest in biogas as an alternative energy resource. With harmonization of good production technologies and backed by various regulations and legislations, the global biogas market is expected to grow significantly over the coming years. Use of biogas not only reduce the emission of harmful gases but also works as an alternative source of energy, giving a hope as a regular and potent energy source for future. Thus use of biogas is not only helping by creating electricity but also helping to reduce the global climate change. Processes to produce biogas on commercial scale with high efficiency are continuously being developed with significant research and development through various governmental and industrial organizations. Owing to rising environmental concerns and use as a significant substitute for energy, the demand of biogas is projected to rise up at an unprecedented rate over the forecast period of 2016-2026. The global biogas market is segmented on the basis of applications and end-users. Based on their applications, the global biogas market is classified in following categories: On the basis of end-users, biogas market is segmented in the following categories: On geographical scale, the global biogas market is segmented into seven key regions, namely North America, Latin America, Western Europe, Eastern Europe, Middle East & Africa, Asia Pacific and Japan. North America and Europe are the most significant regions in the global biogas market. New production technologies and legislations are expected to push the demand and need for biogas worldwide over the forecast period. Global biogas market is emerging with significant growth rate globally. Some of the major players functioning in global biogas market are Air Liquide Advanced Business & Technologies, Vanzetti Engineering S.r.l., EnviTec Biogas AG, Wärtsilä Corporation, Swedish Biogas International AB, Gasrec Ltd., Cryostar SAS, Biofrigas Sweden AB, Scandinavian Biogas Fuels International AB, and Cryonorm BV.

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