Showing papers on "Biogas published in 1984"

Anaerobic wastewater treatment

Abstract: The article reviews the present understanding of bacterial populations involved in anaerobic degradation of organic material into methane and CO2 (biogas); furthermore some recent process developments for anaerobic wastewater treatment are described It could be demonstrated that at least three groups of bacteria are involved in methanogenesis Hydrolytic and acidogenic bacteria first decompose the organic material into various organic acids, alcohols, hydrogen and CO2 The second group of bacteria convert these metabolites into acetic acid, hydrogen and CO2, which are then utilized by the methanogenic bacteria to produce biogas

High rates conversions of soluble organics with a thermophilic anaerobic attached film expanded bed

Abstract: Anaerobic digestion has had limited application because of slow bacterial growth rates, relatively low organic removal ef ficiencies, and the sensitivity of the microorganisms to toxic materials, temperature, and pH. Over the last decade, however, interest in anaerobic digestion has increased. Recent efforts have emphasized: the fundamentals of anaer obic digestion; improvements of the more conventional tech niques such as digestion of animal waste and other agricultural residues and secondary wastewater sludge; reactor design.1-3 The anaerobic attached-film expanded bed (AAFEB) process, de veloped by Jewell and colleagues, was in fact a natural devel opment from existing processes and information on the fun damentals of process limitations.4 This process accumulates large quantities of microbial biomass (30 to 40 kg/m3 volatile solids (VS)), which in turn enables it to efficiently convert dilute sub strates (such as wastewater) to biogas, with minimum sludge yields.

Process and installation for simultaneously producing compost and biogas from organic waste

Abstract: The invention relates to a process for the simultaneous treatment of solid or semi-solid organic waste and liquid organic waste with a view to the simultaneous production of compost and biogas. According to this process, said liquid organic waste is subjected to a liquid-solid separation, the liquid phase from this separation is subjected to anaerobic fermentation in at least one closed digester, the solid phase from said liquid-solid separation is mixed with said solid or semi-solid organic waste, the resulting mixture is subjected to aerobic fermentation at the periphery of said digester and in contact therewith and mud, clarified liquid and gas are respectively discharged from said digester whereas compost from the aerobic fermentation of said solid or semisolid waste is recovered at the periphery of said digester.

Method of degrading organic products, by-products and scraps in an anaerobic medium

Abstract: A method and apparatus for carrying out a degradation in an anaerobic medium, such as a methanogenesis, of organic products, by-products or waste from human, animal and/or plant origin, involving feeding said products to be degraded into a closed fermentation vessel, forcing said products to flow in a direction of circulation within said vessel and recovering the gas produced called biogas evolved above said body of degraded products, with the feeding and/or discharge of the products performed pneumatically, preferably through pneumatic thrust and, according to a preferred embodiment, by injection of gas, preferably biogas. A further improvement comprises using the biogas produced for homogenizing said body of products contained within said vessel, the pressure of injection being in relation to the actual density of the products, in the injection related section.

High-rate anaerobic composting with biogas recovery

Abstract: In Belgium a novel high rate anaerobic composting process with biogas has been developed as an alternative to aerobic systems, producing a commercial dry compost and 60 to 95 cubic metres methane per ton of municipal solid waste. This is a high value energy source simultaneously yielding a stabilized end product. The process was developed so that digestion could take place at 25 to 35% total solids, thus reducing the amount of water needed to dilute the waste, decreasing the digestor volume and cutting transportation costs. The end product is odorless and stable. High rate anaerobic composting of MSW can be combined with sewage sludge stabilization. Manure, vegetable or fruit wastes can be co-treated in certain proportions as required. About 15 to 20% of the energy produced is transformed into electricity and heat and consumed as the waste disposal plant itself. 120 to 140 US $ worth of methane gas and compost can be produced per cubic metre of reactor per year, making anaerobic composting economically attractive.

Method of producing biogas and compost

Abstract: In the mesophile production of biogas, the temperature of the liquid used during anaerobic, methanogenic, fermentation is raised to the required temperature (about 35° C.) by aerobically prefermenting solid substrate at substantially ambient temperature and of appropriate moisture content to raise its temperature to a temperature greater than that required for the anaerobic, methanogenic, fermentation. Thereafter flooding the fermenting solid substrate with the liquid at substantially ambient temperature to increase the temperature of the liquid by heat exchange, and then removing the liquid and storing it in a heat insulated environment to reduce the moisture content of the solid substrate to a suitable degree. The above steps of aerobic prefermenting and flooding are repeated until the liquid has reached the required temperature, and then leaving the liquid in situ to enable anaerobic methanogenic fermentation to take place. In so doing the supply of external heat for the initial warming up of the substrate may be dispensed with, thereby improving the efficiency of the method.

Recovery of biogas

Abstract: Biogas, essentially consisting of 50-70% methane and 30-50% CO2, is scrubbed to remove the C02 by two spray scrubbers (8, 14) arranged in series along the gas flow path The spray scrubbers (8,14) atomise an absorbent liquid which is regenerated and returned to the scrubbers (8, 14) The absorbent liquid is preferably water which is fed under pressure to a regeneration unit (23) where the water is atomised and its pressure is dropped to ambient pressure so forcing out the CO2 which is vented (30) to the atmosphere The water is cooled in a chiller (33) to enhance the solubility of C02 therein and returned to the scrubbers (8,14) The water returning to the first scrubber (8) is thoroughly mixed with incoming biogas in a mixing chamber (6) before entering the scrubber (8) The raw biogas is preferably pre-washed (3) to remove solids and compressed (4) before entering the scrubbers and polished (39) after being scrubbed to remove any remaining contaminants The polished gas may be cooled (48), liquefied (49) and stored in cryogenic tanks (50)

High rate anaerobic digestion of piggery manure with polyurethane sponges as support material

Abstract: The use of polyurethane foam sponges to colonize methanogenic associations for the digestion of piggery manure has been investigated Fermentors containing polyurethane pads as colonization matrix reached a biogas production rate of ca 20 litres per litre reactor per day (30–33°C), hydraulic retention time 75 daysl and a biogas yield of 16 litres per litre piggery manure (7–9% TS) Corresponding control fermentors containing no pads reached a gas production rate of 13 litres per litre reactor per day and only about 10 litres biogas per litre piggery manure

Generation of biogas from Salvinia molesta (Mitchell) on a commercial biogas digester

Abstract: The paper describes the first‐ever successful experiments for utilising the water polluting aquatic weed Salvinia molesta for generation of biogas on a commercial digester The experiments were carried out on a 3 cum capacity, semi continuous type, commercialised biogas digester of KVIC (Khadi and Village Industries Commission, India) design The digester was primarily designed and marketed for biogas production from cowdung and buffalow‐dung It was utilised by the authors with minor modifications to generate odourless combustible biogas from Salvinia molesta The process‐parameters such as:‐ weed:water ratio, pre‐feeding treatment of weeds (to facilitate feeding), temperature etc, worked out earlier by the authors on laboratory scale digesters, were utilized for conducting the trials on the commercial digester The experiments were also carried out with a unique feed biomass consisting solely of Salvinia with no animal dung additive

The construction and operation of a low-cost poultry waste digester.

Abstract: A simple and low-cost poultry waste digester (PWD) was constructed to treat the waste from 4000 caged laying hens on University Research Unit No. 2 at North Carolina State University. The system was built basically of a plastic lining with insulation, a heating system, a hot-water tank, and other metering equipment. It was operated at 50/sup 0/C and pH 7.5-8.0. The initiation of methane production was achieved using the indigenous microflora in the poultry waste. At an optimal loading rate (7.5 kg volatile solids/m/sup 3/ day), the PWD produced biogas (55% methane) at a rate of 4.0 m/sup 3//m/sup 3/ day. The PWD was biologically stable and able to tolerate temporary overloads and shutdowns. A higher loading rate failed to maintain a high gas production rate and caused drops in methane content and pH value. Under optimal conditions, a positive energy balance was demonstrated with a net surplus of 50.6% of the gross energy. For methane production, the PWD system was proved to be technically feasible. The simple design and inexpensive materials used for this model could significantly reduce the cost of digestion compared to more conventional systems. More studies are needed to determine the durability, the required maintenance ofmore » the system, and the most economical method of biogas and solid residue utilization.« less

Inhibition of methanogenesis and its reversal during biogas formation from cattle manure

Abstract: The composition of volatile fatty acids in the biogas digester based on cattle manure as substrate and stabilised at 25°C showed that it contained 87–88% branched chain fatty acids, comprising of isobutyric and isovaleric acids, in comparison to 38 % observed in the digester operating at 35°C.

Design and operation of an upflow anaerobic sludge blanket reactor

Abstract: Wastewater streams with high concentrations of soluble organics and low solids concentrations have historically been treated in aerobic reactors such as activated sludge or trickling filters. In the past, energy costs associated with this process were low, and sludge disposal was easy. However, in recent years, power costs have risen dramatically and sludge disposal has become much more difficult and costly. These changes have significantly reduced the comparative economy of aerobic treatment and led industry to re-examine other treatment technologies. Anaerobic pretreatment of compatible wastes now seems to be very cost-effective compared to aerobic treatment. New advances in treatment technology have significantly reduced the size of anaerobic reactors and improved the stability of the operation. Compared to aerobic treatment, anaerobic treatment requires less power to operate, produces significantly less sludge for disposal, and produces biogas: a mixture of methane and carbon dioxide which can be burned to provide process energy. One example of this advanced anaerobic treatment technol ogy is the upflow anaerobic sludge blanket reactor (UASB). This paper describes how a large potato processor adapted UASB reactor technology to meet increasingly stringent dis charge requirements and provide process energy. Reactor design parameters are outlined and start-up and steady-state operating characteristics are described.

Process for the simultaneous production of biogas and fertilisers

Abstract: A process for the simultaneous production of biogas (CH4 and CO2) and fertilisers from organic wastes (biomass) is composed of the following steps: In a prefermenter (1) conversion of the biomass is carried out by acid-forming microorganisms to form lower organic acids, CO2 and H2. In a main fermenter (2), in which optimal growth conditions for thermophilic microorganisms prevail, these intermediate products are then essentially converted to form CH4 and CO2. Finally, complete exhaustive fermentation of the biomass is carried out in a secondary fermenter (3) at about 70 to 135 DEG C, both additional biogas and also fertiliser being formed. The residence times of the biomass in the individual fermenter vessels (1, 2, 3) are appropriately controlled with respect to optimal energy yield. To increase the operational reliability, the pH is continuously controlled.

Process for producing biogas and apparatus for carrying out the process

Abstract: A process for producing biogas from biomass such as animal faeces with added organic components is described, which supplies biogas which, compared with conventionally produced biogas, has a significantly higher specific calorific value. For this purpose, in a first treatment phase bacterial strains are added to the biomass which produce biogas having a relatively high CO2 fraction from the reaction material. This first treatment phase is followed by a second in which bacterial strains are used which are able to produce methane from CO2. The biogas produced in the first treatment phase is offered to the bacteria active in the second treatment phase as nutrient, as it were. In an apparatus suitable for carrying out the process according to the invention, reaction chambers suitable for the individual treatment phases are thermally well insulated from each other and can be heated to the particular reaction temperatures at which the bacteria used for each respective purpose develop most expediently.