Factors affecting the efficiency of biogas plants

The intensive development of agriculture inevitably leads to an increase in the volume of organic waste. Residue disposal technologies are often based on anaerobic digestion processes occurring in biogas plants.

In order to increase the efficiency of the operation of biogas plants, plants with a high organic matter content are used as substrates. For this purpose, target energy crops are grown - mainly corn and grasses, from which silage is produced. Animal waste and food waste are also used as raw materials for the implementation of biogas production processes.

The product of a biogas plant is biogas, which is classified as a renewable energy source because it contains methane. The produced gas, biogas, is an energy carrier that can be easily converted into electricity and heat energy http://max64.ru/.

The process of anaerobic digestion is one of the most adequate and promising methods of utilization of organic waste, and a source of biofuel. However, the process must be stable and cost effective.

The main factors affecting the efficiency of biogas plants are the physicochemical composition of the substrates, acidity, process temperature, the implementation of the effective mixing process, dry residue, the content of organic matter in the substrate, the level of loading of the digester, the concentration of inhibitors. These parameters are monitored both at industrial and low-power and home biogas plants.

Even minor changes in the conditions of anaerobic fermentation can significantly disrupt the process of biogas production or completely stop it. Fermentation temperature is one of the factors that significantly affect the course of the biogas production process. Minor changes in temperature and exposure time affect the activity of methanogenic bacteria. As a result, biogas production can be significantly reduced.

So, in Europe, the mesophilic fermentation temperature mode prevails at a temperature of about 39 degrees Celsius, but the thermophilic fermentation mode is also used, in which more thermal energy is used to maintain the production process.

Another important indicator affecting the efficiency of biogas production is the acid number of the feedstock that is fermented. The acidity of the medium should be in the range of 6.8-7.5, since such conditions guarantee optimal conditions for maintaining bacterial life and reproduction of methanogenic bacteria at all four stages of the fermentation process. The biogas yield drops, both if the acidity is higher than 7.5, and if the indicator is below 6.8.

When biomass enters the digester with high protein feedstock, large volumes of ammonia nitrogen are generated. Excess ammonia slows down the production of biogas. As the fermentation temperature rises, the effect of ammonia is enhanced, inhibiting methane fermentation.

Certain organic raw materials are rich in sulfur and grow rapidly when fermented, which is a problem. A higher temperature of anaerobic fermentation increases the solubility of hydrogen sulfide, which leads to a higher concentration in the liquid fraction of the fermented substrate.

During the start-up period of the biogas plant, it is very important to supply the substrate in small portions with a homogeneous composition. This approach allows you to achieve normal fermentation at every stage of the production process.

Also, during the fermentation of substrates of plant origin, it is important to observe the appropriate residence time in the digester. This is done in order to achieve the required level of decomposition of the organic component.

The above indicators are the most common causes of problems in the operation of biogas plants, since they directly affect the actual production of biogas.

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10 Sep 2020