Sludge Biogas Research Articles

Potential of Palm Oil Empty Fruit Bunch as Biogas Substrate

Natural gas is a source of energy that comes from the earth which is depleting every day, an alternative source of energy is needed and one of the sources comes from biogas. There is an abundance of empty fruit bunch (EFB) that comes from palm oil plantation that can become a substrate for biogas production. A methodology of fermentation based on Verein Deutscher Ingenieure was used to utilize EFB as a substrate to produce biogas using biogas sludge and wastewater sludge as inoculum in wet fermentation process under mesophilic condition. Another optimization was done by adding a different water ratio to the inoculum mixture. In 20 days, an average of 6gr from 150gr of total EFB used in each sample was consumed by the microbes. The best result from 20 days of experiment with both biogas sludge and wastewater sludge as inoculum were the one added with 150gr of water that produced 2910ml and 2185ml of gas respectively. The highest CH 4 produced achieved from biogas sludge and wastewater sludge with an addition of 150gr of water to the inoculum were 27% and 22% CH 4 respectively. This shows that biogas sludge is better in term of volume of gas that is produced and CH percentage.

Olive Mill Industrial Waste as Co-substrate in Anaerobic Digestion with Aim at its Energetic Exploitation

The aim of this paper is to assess the feasibility of the co-digestion of olive mill industrial waste with urban sewage sludge from wastewater treatment plants (WWTP). These wastes include olive mill solid waste (OMSW) and olive mill effluent (OME). This co-digestion process enables the energetic exploitation of OMSW and/or OME and introduces an environmental solution for their highly pollutant compounds. The behaviour of both co-substrates was studied using biochemical methane potential assays. To determine the optimal proportions of each co-substrate, different quantities of OME and OMSW were added to a constant quantity of substrate (urban sewage sludge) and put to test. A small amount of digested sludge from WWTP was used as an inoculum to accelerate the pace of the reactions. Thus, the optimal proportions between substrate and co-substrate were defined. The samples containing OMSW showed a biodegradability around 23%, slightly above that of the substrate on its own (21.3%). Moreover, biogas production in samples containing OMSW was significantly superior to samples containing substrate only. Nevertheless, the samples containing OME as a co-substrate presented an inferior biodegradability (20.3%) to that of the substrate on its own. Similarly, biogas production in OME co-digestion remained within the usual values of urban sewage sludge biogas production. In all cases, the system remained stable and the energetic efficiency of the process was improved in comparison to the digestion of substrate only. Therefore, co-digestion with urban sewage sludge proves to be a cost-effective method for OMSW and OME environmental management.

Produktivitas Tanaman padi (Oryza sativa L.) Segreng Terhadap Aplikasi Sludge Biogas di Lahan Sawah Desa Wukirsari, Cangkringan, Sleman

Rice ( Oryza sativa L.) is a main crop agriculture in Indonesia. Biogas sludge is the residue of cattle during processing in the biogas that has lost its gas and rich with macro elements – N, P and K as well as micro elements such as Ca, Mg, Fe, Mn, Cu and Zn. Biogas sludge has not been well utilized by the citizens. This study examined the productivity of rice cultivars Segreng to biogas sludge application on field. The objective of this research was to find the best dose of sludge and to study the productivity of rice cultivars Segreng after sludge application on crop field. Research was conducted in 100 m 2 of field. The biogas sludge concentration used in this research was 5 variations; (1) 0 ml, (2) 1000 ml, (3) 2000 ml, (4) 3000 ml, dan (5) 4000 ml. The planting system used is TAJARWO. The productivity parameter measured were Nitrate Reductase Activity (NRA), dry weight, number of grain per plant and grain weight. Environment parameters were temperature, pH, humidity and light intensity. The data was analyzed with ANOVA and followed by DMRT at significant level of 5%. The results revealed that the highest rice productivity was seen in treatment 2000 ml sludge/100m 2 with 31 gr of dry weight, 483 number of grains per plant and 30.000 kg/100m 2 of grain weight. The best sludge dose present on 2000 ml/100m 2 .

Optimization of the Use of Farm Waste and Water Hyacinth for Earthworm (Lumbricus rubellus) Cultivation Media

This study aimed to determine the effect of water hyacinth addition to farm waste on the number of earthworms, earthworm weight, media shrinkage, vermicompost quality, and the sustainability and sensitivity of earthworm farming. The study was prepared using a completely randomized design with two different factors, the water hyacinth (media without water hyacinth and media with 5% water hyacinth addition) and raw materials from farm waste (chicken and cow manure, and biogas sludge from chicken and cow manure), with three replications for each treatment. The results showed that the addition of water hyacinth to raw materials from farm waste had a very significant effect on the number of earthworms, earthworm weight, media shrinkage, vermicompost quality (except for P2O5 level that had no significant increase). When manure is to be added to the cultivation media, it is recommended to use cow manure, while both types of biogas sludge (from chicken and cow manure) are good for the cultivation of earthworm. Based on the study of sustainability, the use of farm waste and water hyacinth as media to raise earthworm gives a positive value in economic and environmental aspects. Therefore, it has great potential.

Physiological Response of 'Segreng' Rice Plant (Oryza sativa L.) to Biogas Sludge at Wukirsari Village, Cangkringan, Sleman

Wukirsari Village, Cangkringan District is belong to Merapi Mountain’s slopes which located between the Gendol River and Yellow River. Nowadays, we faced the problem of anorganic fertilizer overused such as Urea, ZA, TSP/SP-36 and KCl in agriculture land. The effort to return the soil organic compound can be done by added some organic compounds or microbial bio -organic fertilizer. Sludge is fermented biodigester yield and it has lost its gas. The aim of this research was to understand the physiological response and optimum dose of biogas as planting medium to ‘Segreng’ Rice planted in the rice field of Wukirsari Village, Cangkringan District, Sleman Regency. This research was done on greenhouse scale and rice field scale. The treatment given on 0; 1; 1,5; 2 and 2,5 liters per 100 m2 of rice field areas, and given on 0; 4; 8; 12; and 24 ml per 5 kg soil on polybags. Data were taken in three repetitions. The vegetative growth parameters included plant height, number of leaves, number of seedlings and chlorophyll content, while generative growth parameters measured included NRA levels, dried biomass including crown/stem, roots, filled grains, empty grains, and total weight and number of filled grains, empty rains, and the number of panicles. The result were tested with ONE WAY ANOVA (Analysis of Variance) with SPSS version 19 for Windows and followed by Duncan's Multiple Range Test with 95% significance level (α = 0.05). Generally, the result showed that biogas sludge can increase the vegetative and generative growth of rice plant ‘Segreng’ on polybag scale and rice field scale. The rice plant on polybag with 4 ml biogas sludge was significantly different on the vegetative growth and chlorophyll content, while the rice plant on polybag with 8 ml biogas sludge was significantly different on the generative growth and NRA levels.

Characterisation and cleaning of biogas from sewage sludge for biomethane production

This study investigates the conversion of sewage sludge from wastewater treatment plants (WWTP) into biomethane for automotive fuel or grid injection. A prototype plant was monitored in Northern Italy, based on vacuum swing adsorption (VSA) on synthetic zeolite 13×: this biogas upgrading method is similar to pressure swing adsorption (PSA) and commonly used for other kinds of biomass. Measurements of biogas inlet, biomethane outlet and off-gas were performed including CH4, CO2, CO, H2, O2, N2, HCl, HF, NH3, H2S and volatile organic compounds (VOCs). Critical levels were observed in the biogas for of H2S and HCl, whose concentrations were 1570 and 26.8 mg m−3, respectively. On the other hand, the concentration of halogenated VOCs (including tetrachloroethylene and traces of perfluoroalkilated substances, PFAS) and mercaptans were relatively low. A simultaneous and reversible adsorption on 13× zeolite was achieved for H2S and CO2, and carbon filters played a minor role in desulfurisation. The presence of HCl is due to clarifying agents, and its removal is necessary in order to meet the required biomethane characteristics: an additional carbon-supported basic adsorbent was successfully used to remove this contaminant. This study also highlights the interference of CO2 towards HCl if sampling is performed in compliance with the new EU standard for biomethane. High total volatile silicon (TVS) was confirmed in sewage sludge biogas, with a major contribution of siloxane D5: the suitability of this compound as an indicator of total siloxanes is discussed. Results demonstrate that volatile methyl siloxanes (VMS) do not represent a critical issue for the VSA upgrading methodology.

Hydrothermal carbonization of agricultural residues: A case study of the farm residues -based biogas plants

Hydrothermal carbonization (HTC) of biomass is a promising method to produce carbonaceous materials. The work presented in this article addresses the application of hydrothermal carbonization (HTC) to produce a solid fuel named HTC-Biochar, whose characteristics are comparable to lignite coal. Biogas sludge (SD), maize silage (MS), and barley silage (BS) as a substrates were hydrothermally carbonized in a 1.5 L batch reactor at 200 °C for 6 h. The effect of mixing ratios of different substrates on HTC was investigated. Chemical compositions and combustion characteristics of hydro-chars obtained from mono- and co-carbonization were evaluated. Result showed that HTC increased carbon contents and higher heating values (HHV) by 1.4–14.4% and 13–36%, respectively. The evolution of the H/C and O/C atomic ratios indicated that dehydration and decarboxylation occurred during hydrothermal carbonization for all samples. Furthermore, a significant synergistic enhancement was observed for HHV and carbon content. A mixing ratio of 1:1 for BS and SD showed the best performance for co-HTC. In summary, hydrothermal co-carbonization is a promising strategy to tailor high-performance hydro-char for energy applications.

Pengaruh Media Tanam dan Jenis Tanaman Terhadap Produksi Nutrien Bagian Aerial Tanaman Sorgum dan Jagung

This research aims to know the biogas sludge utilization on planting media by looking at the difference in production of sorghum and maize crops. This research was conducted on November 2015 until January 2016 in the area around cultivation of Izzah Sejahtera Farm cattle farm, Jagoan Village, Sambi District, Boyolali District. The material used is planting land, sludge biogas, sorghum and corn seed. The research design used was a complete randomized design of 2 x 2 factorial pattern. The research consisted of two treatment factors namely plant effect (Factor A) and difference of land type (Factor B). Plant factor consists of 2 levels, namely sorghum and corn. Land type difference factor consists of 2 levels, ie land without sludge biogas and land with sludge biogas. The treatment in this study, namely T1P0: Sorgum grown on soil without sludge biogas, T1P1: Sorgum grown on soil with sludge biogas, T2P0: Corn grown on soil without sludge biogas, T2P1: Corn grown on soil without sludge biogas . Each plant consists of 96 plants divided into two, P0: 48 plants and P1: 48, so there are 192 units of experiment. The data obtained were analyzed by analysis of variance to know the difference of treatment to the observed variables based on F test of 5% level and if there is a significant difference then continued to analyze with Duncan's Multiple Range Test (DMRT) 5%.

Primary and Activated Sludge Biogas Production: Effect of Temperature

Sewage sludge management is a problem of growing importance. Anaerobic sewage sludge stabilization is commonly used technology, where organic matter contained in primary and activated sewage sludge is converted into biogas, so both, pollution control and energy recovery can be achieved. The paper deals with the effect of process temperature (36 °C, 42 °C and 50 °C) on biogas production and quality during anaerobic stabilization of primary and activated sewage sludge generated during purifying process in low‑loaded activated sludge process. Primary and activated sewage sludge samples were taken at the wastewater treatment plant Brno, Czech Republic. The characteristics of sludges (dry matter and organic dry matter content, pH, conductivity, redox potential) were dermined. Biogas production and quality was measured using 3 anaerobic systems, each of 8 batch anaerobic fermenters, at the 3 different temperature conditions 36 °C, 42 °C and 50 °C. Hydraulic retention time was 20 days. Hypothesis, which predicts that the fermentation of primary and activated sludge provides dissimilar methane quantity and quality under different temperature conditions (36 °C, 42 °C and 50 °C), was partially confirmed. Temperature 42 °C significantly increased biogas production from primary sewage sludge (by 60 % in comparison with production at 36 °C). For activated sewage sludge samples no significant influence of temperature on the biogas production was observed.

Activated Carbon As A Support In Biotrickling Filters For The Removal Of Siloxanes In Sewage Sludge Biogas

Activated Carbon As A Support In Biotrickling Filters For The Removal Of Siloxanes In Sewage Sludge Biogas

Effects of Adding Chicken Blood Meal and Fishmeal to Sludge Biogas as White Oyster Mushroom Media.

The biogas sludge is generally not used optimally and people even pour it directly into the river that it cause environmental pollution. One of the ways to get the benefit from sludge and chicken blood meal or fishmeal is to use it as a substitute for bran in mushroom media. This study aimed to improve the nutrient content of biogas sludge with the addition of chicken blood meal (CBM) and fishmeal (FM) as substitute material for bran in white oyster mushroom media. The biogas sludge was dried in the sun for 3 days until its form resembled the soil. The treatment consisted of dried biogas sludge without CBM (BP0), dried biogas sludge with 1% CBM (BP1) and dried biogas sludge with 3% CBM (BP2). Each was added to the media of white oyster mushroom as much as 15% as substitute material for bran. The other treatment consisted of dried biogas sludge without FM (FP0), dried biogas sludge with 2% FM (FP1) and dried biogas sludge with 4% FM (FP2). Each was added to the media of white oyster mushroom as much as 5% as substitute material for bran. BP0 and FP0 created from white oyster mushroom media were commonly used by farmers. Each treatment was analyzed of nutritional and biological contents. All the data were tested using completely randomized design one-way ANOVA. The results of the research on the use of chicken blood meal and fishmeal showed that the best treatments were BP2 and FP2. Their nutrient content increased, including the organic-C, organic matter, nitrogen, P2O5 and K2O. The productivity of the oyster mushroom increased, shown by the increase of fresh weight and diameter of caps in treatment BP2. The replacement of bran by biogas sludge with 4% FM addition (FP2) in oyster mushroom media increased the fresh weight, the number of caps and the length of oyster mushroom stalks. The best treatments for mushroom media were BP2 and FP2 to be used as substitute material for bran in white oyster mushroom media.

Improving waste-to-energy process by co-digestion of exhausted coffee biowaste and WWTP sludge

The purpose of this study is to investigate the effects of using pre-treated exhausted coffee biowaste (ECB) as a co-substrate to optimize sewage sludge (SS) biogas production. The trials were conducted in semi-continuous mode at mesophilic conditions (36 ± 1ºC) with a Hydraulic Retention Time of 17 days and an average organic loading rate (0.94 ± 0.05 g VS Lreactor.day-1). An anaerobic co-digestion trial (T1) was assessed using a feeding mixture with a ratio of SS (80 %) and LECB (20%), v:v, and compared against a reference scenario (T0). Results showed that the addition of the co-substrate had a significant influence on specific methane production (3 times higher) and biogas quality (12% higher), which is a feasible strategy towards self-sufficient wastewater treatment plant. Furthermore, the stability along assays was ensured monitoring the digestate characteristics (pH, electrical conductivity, total alkalinity and ammonia content) and the specific energy loading rate.

Efektifitas Produksi Nutrien Tanaman Sorgum dan Jagung Bagian Aerial dengan Media Tanam yang Berbeda

This research aims to know the utilization of biogas sludge on different planting media towards the production of sorghum and corn plant nutrient. This research was carried out in izzah beef cattle multifarm in the jagoan village, Boyolali District, while the proximat analysis was performed in the laboratory of Nutrition Food Science, Major In Farm, Faculty Of Agriculture, Sebelas Maret University, Surakarta. The material used is plantation land containing sludge biogas, seed sorghum, maize seeds and water. The research design used was randomized complete design with factorial pattern 2 treatment. Each treatment consisted of 3 units each experiment there are 4 groups of units of plants. Treatment in the form of land containing sludge (P1) and land that does not contain sludge (P0), as well as sorghum plants (T1) and corn plants (T2). The observed variables, namely the production of dry ingredients, protein production, production of organic matter and total production of digestible energy. The data obtained were analyzed for the presence of variansi difference in the treatment of variables based on the F-test level 5% and if there is a noticeable difference followed by test Duncan's Multiple Range Test (DMRT) levels 5% as well as the analysis descriptive. Variansi analysis results with different land treatment indicates that there is a real difference between dry ingredients production towards varieties of plants and the very real differences occur towards the production of organic materials, the production of protein crude and total production of digestible energy between varieties of plants.

Assessment of two carrier materials for phosphate solubilizing biofertilizers and their effect on growth of wheat (Triticum aestivum L.)

Biofertilizers are usually carrier-based inoculants containing beneficial microorganisms. Incorporation of microorganisms in carrier material enables easy-handling, long-term storage and high effectiveness of biofertilizers. Objective of the present study was to assess enriched biogas sludge and soil as biofertilizer carriers on growth and yield of wheat. Six phosphate solubilizing strains were used in this study. Three phosphate solubilizing strains, 77-NS2 (Bacillus endophyticus), 77-CS-S1 (Bacillus sphaericus) and 77-NS5 (Enterobacter aerogenes) were isolated from the rhizosphere of sugarcane, two strains, PSB5 (Bacillus safensis) and PSB12 (Bacillus megaterium) from the rhizosphere of wheat and one halophilic phosphate solubilizing strain AT2RP3 (Virgibacillus sp.) from the rhizosphere of Atriplex amnicola, were used as bioinoculants. Phosphate solubilization ability of these strains was checked in vitro in Pikovskaya medium, containing rock phosphate (RP) as insoluble P source, individually supplemented with three different carbon sources, i.e., glucose, sucrose and maltose. Maximum phosphate solubilization; 305.6μg/ml, 217.2μg/ml and 148.1μg/ml was observed in Bacillus strain PSB12 in Pikovskaya medium containing sucrose, maltose and glucose respectively. A field experiment and pot experiments in climate control room were conducted to study the effects of biogas sludge and enriched soil based phosphorous biofertilizers on growth of wheat. Bacillus strain PSB12 significantly increased root and shoot dry weights and lengths using biogas sludge as carrier material in climate control room experiments. While in field conditions, significant increase in root and shoot dry weights, lengths and seed weights was seen by PSB12 and PSB5 (Bacillus) and Enterobacter strain 77-NS5 using biogas sludge as carrier. PSB12 also significantly increased both root and shoot dry weights and lengths in field conditions when used as enriched soil based inoculum. These results indicated that bacterial isolates having plant beneficial traits such as P solubilization are more promising candidates as biofertilizer when used with carrier materials.

PERSEPSI MASYARAKAT KABUPATEN BANJAR TERHADAP PEMANFAATAN ENERGI BIOGAS DAN KUALITAS PUPUK LIMBAH BIOGAS

Research takes place in three villages (Danau Salak, Pengaron, Indrasari). The aims of research are want to know the perception due to build biogas unit (adventage, point plus, obstacle and environment impact), nutrition N, Pand K from solid waste of biogas sludge, and percentage of efficiency fuel that can used by society. Research divided in two steps, first step is want to know the perception of society and the second step is want to know nutrition quality from solid waste from biogas sludge. The first step using Randomized Design method with 4 treatment and 4 replicated. The treatment are kind of raw material used in biogas process, that are : B0 (cattle feces), B1 (chicken feces), B2 (sheep feces) and B3 (duck feces), so needed 16 biogas digesters. Quality nutrition of solid waste of biogas sludge are measured at laboratory.The second step using survey method using 16 respondents from 3 villages and data was analyzed by Kruskal Wallis. Result of the research show, the first step that the difference of raw material (kind of animal feces) not give the real differences on advantages, point plus, obstacle and invironment impact, but the biogas from cattle and sheep feces produce higher efficiency about 41,37% ( 120.000 rupiahs) from chicken and duck feces that produce efficiency only about 20,69% (60.000 rupiahs). The result of second step show the fertilizer from solid waste of biogas sludge that using cattle feces produce the highest nitrogen (N, 1,82% equivalent PK 11,37%) comparing with other treatment, and the best to using as fertilizer .

Comparison of biogas sludge and raw crop material as source of hydrolytic cultures for anaerobic digestion

Mixed fermentative/hydrolytic bacteria were enriched on lignocellulose substrates in minimal medium under semi-anaerobic mesophilic conditions in the presence or absence of natural zeolite as growth supporter to ultimately bioaugment non-adapted sludge and thereby enhance the overall anaerobic digestion (AD) of recalcitrant plant material. Desired enzyme activities, i.e. xylanases and cellulase were monitored during subsequent cultivation cycles. Furthermore, enriched microbial communities were characterized by 16S rRNA-based 454-Pyrosequencing, revealing Firmicutes, Bacteriodetes, Proteobacteria and Spirochaetes to be the predominant bacterial groups in cultures derived from anaerobic sludge and raw crop material, i.e. maple green cut and wheat straw as well. Enriched populations relevant for biopolymer hydrolysis were then compared in biological methane potential tests to demonstrate positive effects on the biogasification of renewable plant substrate material. A significant impact on methane productivity was observed with adapted mixed cultures when used in combination with clinoptilolite to augment and supplement non-adapted bioreactor sludge.

Inocula selection in microbial fuel cells based on anodic biofilm abundance of Geobacter sulfurreducens

Microbial fuel cells (MFCs) rely on microbial conversion of organic substrates to electricity. The optimal performance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this microbial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were evaluated for three inocula including domestic wastewater (DW), lake sediment (LS) and biogas sludge (BS) with varying substrate loading (Lsub) and external resistance (Rext) on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The LS inoculated MFCs showed highest abundance (18%±1%) of G. sulfurreducens, maximum current density [Imax=(690±30)mA·m−2] and coulombic efficiency (CE=29%±1%) with acetate as the substrate. Imax and CE increased to (1780±30)mA·m−2 and 58%±1%, respectively, after decreasing the Rext from 1000Ω to 200Ω, which also correlated to a higher abundance of G. sulfurreducens (21%±0.7%) on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Rext for optimizing electricity generation in MFCs.

Increase of methane formation by ethanol addition during continuous fermentation of biogas sludge.

Very recently, it was shown that the addition of acetate or ethanol led to enhanced biogas formation rates during an observation period of 24h. To determine if increased methane production rates due to ethanol addition can be maintained over longer time periods, continuous reactors filled with biogas sludge were developed which were fed with the same substrates as the full-scale reactor from which the sludge was derived. These reactors are well reflected conditions of a full-scale biogas plant during a period of 14days. When the fermenters were pulsed with 50-100mM ethanol, biomethanation increased by 50-150%, depending on the composition of the biogas sludge. It was also possible to increase methane formation significantly when 10-20mM pure ethanol or ethanolic solutions (e.g. beer) were added daily. In summary, the experiments revealed that "normal" methane production continued to take place, but ethanol led to production of additional methane.

Short-term effect of acetate and ethanol on methane formation in biogas sludge.

Biochemical processes in biogas plants are still not fully understood. Especially, the identification of possible bottlenecks in the complex fermentation processes during biogas production might provide potential to increase the performance of biogas plants. To shed light on the question which group of organism constitutes the limiting factor in the anaerobic breakdown of organic material, biogas sludge from different mesophilic biogas plants was examined under various conditions. Therefore, biogas sludge was incubated and analyzed in anaerobic serum flasks under an atmosphere of N2/CO2. The batch reactors mirrored the conditions and the performance of the full-scale biogas plants and were suitable test systems for a period of 24h. Methane production rates were compared after supplementation with substrates for syntrophic bacteria, such as butyrate, propionate, or ethanol, as well as with acetate and H2+CO2 as substrates for methanogenic archaea. Methane formation rates increased significantly by 35 to 126% when sludge from different biogas plants was supplemented with acetate or ethanol. The stability of important process parameters such as concentration of volatile fatty acids and pH indicate that ethanol and acetate increase biogas formation without affecting normally occurring fermentation processes. In contrast to ethanol or acetate, other fermentation products such as propionate, butyrate, or H2 did not result in increased methane formation rates. These results provide evidence that aceticlastic methanogenesis and ethanol-oxidizing syntrophic bacteria are not the limiting factor during biogas formation, respectively, and that biogas plant optimization is possible with special focus on methanogenesis from acetate.

Quantification of methanogenic heterodisulfide reductase activity in biogas sludge

Methanogenic archaea are essential for the production of methane in biogas plants. Here we present enzymatic test systems for the analysis of the metabolic activity of methanogens based on the heterodisulfide reductase reaction. The first rapid test shows that heterodisulfide reductase can be detected in 1g of biogas sludge after sonication and centrifugation. The resulting cell lysate used reduced methylviologen for heterodisulfide reduction, a reaction that is specifically catalyzed by methanogenic heterodisulfide reductase. In the second test cell lysate from 60g of biogas sludge was separated by ultracentrifugation. Both, cytoplasmic membrane and cytoplasmic fractions revealed heterodisulfide reductase activity, indicating the presence of hydrogenotrophic and aceticlastic methanogens, respectively.