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BIOGAS UPDATE VIA BIOLOGIC CO2 CONVERSION AND H2 INTO CH4. - Biogas has become one of the main sources of renewable energy in the EU, overtaking petrol by more than 12% for the last 15 years. Currently, the main use of biogas is the combined production of heat and electricity in cogeneration plants. However, some factors are changing this trend: The low efficiency of combustion due to the presence of carbon dioxide (25-50%), the reduction of electrical tariffs originating from biogas and political instabilities in Europe’s natural gas supply are behind the continent’s huge expansion of biogas improvement plants. Improved biogas can be used either as a fuel (pumped into the grille of natural gas) or liquefied as natural gas. http://envtech.uva.es/pdf/PBiogas%20upgrading%20H2.pdf PRE-TREATMENT OF BIOGAS EXPLOSIONS IN LOCAL QUAGMIRES IN ORDER TO IMPROVE ENERGY BALANCES IN EDAR. - Political and social demands for the sustainable use of energetic resources have motivated the water industry to intensify energy saving efforts. Besides the huge costs of electricity and other power loads, water companies have been meeting their customers’ environmental awareness. The water resources management confirmed that the energy’s demand for Sewage Treatment Plants (EDAR) constitute an important part of the total power consumption. Part of this energy can be regained by exploiting sewage’s energy potential to transform organic matter into biogas, since mud is the only current able to produce energy in an EDAR. Subsequently, the obtained biogas could be used for elctricity and heat generation or directly consumed for other EDAR processes. The medium term target for turning into an EDAR with neutral or even positive energy seems viable by implementing sludge treatments before anaerobic digestion. In this way, thermal hydrolysis “steam explosion” is widely used to increase methane production. At the same time, the term “explosion of ammonia” is used within the field of straw hydrolysis. http://envtech.uva.es/pdf/P-Biogas_Explosion_Pre-Treatment.pdf OPTIMIZATION OF BIOGAS PRODUCTION THROUGH ALGAE BIOMASS - Microalgae ability to attach CO2, nutrients (N, P) and storing solar energy in theit cells through photosyntesis makes them an interesting alternative of green energy ( (biofuel and biogas) and sewage treatment technologies. In comparison to conventional plants, microalgae have higher growth rates and can be grown in non-arable land. For this reason, microalgae grown for biogas production can’t compete with crops for human nutrition. The use of microalgae in sewage treatment results in bigger amounts of biomass that need to be removed. Likewise, biodiesel production through microalgae would generate huge amounts of algae waste. An alternative to this residual biomass’ waste is anaerobic digestion, which transforms this waste into CH4, which can, in turn, be transformed into different kinds of energy (heat, electricity, etc). - http://envtech.uva.es/pdf/P-Algae_Digestion.pdf CHARACTERIZATION OF THERMAL HYDROLYSIS AND ANAEROBIC DIGESTION COMBINED PROCESS IN A PILOT PLANT - In a conventional sewage treatment plant, around 60% of sewage waste turns into mud handled in anaerobic digestion for its stabilization and biogas production. However, anaerobic digestion presents some drawbacks, such as a long time of hydraulic retention (over 20 days), a high digestion volume (high cost) and a degradation rate limited by the organic matter during the hydrolytic phase. This way, the procedure’s improvement is linked to the hydrolysis phase’s improvement. A bigger and faster degradation could be achieved by increasing the solubilization of undissolved compounds, breaking them into monomers more accessible to anaerobic bacterias. It is therefore necessary to introduce a pretreatment unit before the digestor. Thermal hydrolysis sticks out among the other alternative treatments (mechanical, biological, ultrasound...). Its main advantage is that the need for thermal energy can be satisfied by the energy generated in the process, thus obtaining an energetically self-sufficient system. Even though thermal hydrolysis has been widely studied in literature, most investigations have examined the point of view of the laboratory scales for the lot biodegradability test. However, in order to obtain reliable technological data and to establish the calculation bases of a future plant, it is necessary that a pilot plant quantifies not only the biogas output but also its characteristics. http://envtech.uva.es/pdf/P-Thermal_Hydrolysis.pdf SECONDARY SLUDGE AUTOHYDROLYSIS PREPARATION FOR ANAEROBIC DIGESTION IMPROVEMENT - Secondary sludge is produced during the biological treatment in the activated sludge process of sewage treatment plants and consists of active micro-organism floccules. The resultant sludge must be treated by trying to reduce the amount of water and organic matter. It also seeks to produce a stabilized and reusable efflluent, mainly using grade A biosolids and using the energetic content of organic matter. Anaerobic digestion is the most popular treatment for sludge elimination in EDAR. The biogas production has been tied to renewable energy sources and a low energy requirement. Hydrolisis is the limiting step for anaerobic digestion of secondary sludge, since it is necessary to break the sludge floc and the membrane cell. Several techniques have been proposed to improve sludge hydrolysis if anaerobic digestion pre-treatments show interesting results. There are many sludge pre-treatments using different mechanic processes (chemical, sonication, thermal and use of hydrolytic enzimes) The option of hydrolytic enzymes includes the possibility of using: (1) commercial enzymes, (2) enzyme producing microorganisms, (3) enzymatic system of pre-treated sludge. If the environmental conditions of sludge were changed, it would be possible to stimulate the production of hydrolytic enzymes such as proteases and then producing a metter hydrolysis of the organic matter. - http://envtech.uva.es/pdf/P-Thermal_Hydrolysis.pdf MICROAEROBIC PROCESSES FOR H2S DISASSEMBLING AND IMPROVEMENT OF THE PROCESS’ CONSISTENCY - Anaerobic digestion (AD) of organic waste is capable of transforming a big part of organic matter into biogas, 60-70 (v / v)% of methane, which can be energetically recovered, thus destroying most pathogens present in the sludge and limiting every possible odor problem related to residual putrefying matter. As a result, AD is a widely used method in the sewage sludge treatment, and in local and agricultural solid waste and high organic waste sewage treatment plants. However, the huge diversity of microorganisms involved in the transformation of complex compounds into simpler compounds that can be turned into methane requires a balance between intermediary products, in a way that environmental conditions allow microorganisms to appropriately use organic matter. Intrinsic variations in organic residual charges may result in the accumulation of intermediaries and consequently, to the process’ failure. In addition, when sulphur compounds are available, hydrogen sulphide is produce in a different degree with several associated problems. Hydrogen sulphide is corrosive and damages considerably the facilities’ shelf life. It’s also toxic for living beings, it causes inhibition problems in microorganisms and has a strong smell. http://envtech.uva.es/pdf/PMicroaerobic.pdf METHANOL PRODUCTION FROM BIOGAS - Nowadays, one of the main environmental problems is the presence of carbon dioxide in the atmosphere, which causes the infamous greenhouse effect. This is why CO2 is trying to be captured and recovered. Some of the techniques used allow this compound to be reused. For example, in metanol production which has a great importance in chemical industries. Also, methanol can be used as a fuel and sometimes even substitues gasoline. Methanol production through selective carbon dioxide hydrogenation is a new technological alternative to capture and reuse CO2. When CO2 and methane are combined (as happens in biogas), it can be used as a carbon source in methanol synthesis in accordance with the reaction of vapor methane, where the gases formed in the methane’s alteration act as an alcohol precursor. - http://envtech.uva.es/pdf/P-Methanol.pdf TREATMENT OF SEWAGE WITH MEMBRANE TECHNOLOGY- The main advantage of membrane technology is the capability of disconnecting the hydraulic retention time (HRT) and the sludge retention time (SRT). This can be achieved because the membrane works as a barrier, keeping the solids within the reactor. A sludge trap is not necessary and the concentration of solids in the mixture may be higher. The more solids in the reactor, the bigger the possibility of working with higher organic loading rates, with consequential space reduction. The process of activated sludge operates at an organic charge of 5 to 10 grams of chemical Oxygen Demand (COD) per liter, while a membrane bioreactor can go up to 60 grams of COD/L, which implies a 10 to 12 times bigger reduction in space. A higher SRT is also an advantage, since it allows bacteria with a low growth rate to develop in the liquid phase, thus improving efficiency. - http://envtech.uva.es/pdf/P-Membrane.pdf

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