PRINCIPLE OF BIOGAS PLANT
Any biogas complex is constructed to produce biogas from organic substrates. The principle of its operation is based on anaerobic fermentation. Biogas production occurs as a result of bacteria processing the organic substrate without oxygen. In this process, complex molecules are decomposed into fatty acids, monosaccharides and amino acids. Of these, alcohols and other lower compounds are formed by oxidation, which then turn into acetic acid. At the last stage, biochemical reactions lead to the formation of methane and carbon dioxide, which are the main components of biogas.
Biogas plant as a means of waste disposal
Biogas production is not the only goal of a biogas plant. An important factor is that the main raw materials for its work are organic waste from the food industry and agriculture. Often, the removal and disposal of such production residues is expensive. Utilization of waste in biogas plants brings not only environmental benefits, but also gives a positive financial effect. Biogas from the plant is burned in cogenerators to produce heat and electricity, which gives an increase in the income of the enterprise.
As a substrate for the production of biogas use:
- waste from dairy, beer, vegetable processing, sugar production (whey, beer pellet, fruit and vegetable squeezes, molasses, pulp, etc.);
- crop by-products (straw, silage, pulp);
- bird droppings, dung of pigs and cattle;
- organic part of municipal solid waste;
- catering waste;
- sediment of municipal and industrial wastewater treatment plants, sludge, activated sludge.
A biogas plant for silage, manure or a combination of raw materials is the most common type of project in Ukraine.
Biogas plant – basic structural elements
A biogas station is a complex engineering facility consisting of several modules integrated into a single system. We provide an indicative list of equipment and subsystems that are included in a particular combination of a biogas plant.
- The storage system of the substrate (biomass).
- The module for weighing and feeding dry types of substrate.
- The loading module of the liquid substrate.
- Digester and after-digester.
- The substrate heating system (temperature support).
- The mass transfer system in the fermenter (mechanical mixing, hydraulic or bubble).
- Gas holder and gas facilities.
- Biogas purification system.
- A separator for separating the liquid and solid fractions of the spent substrate (obtaining liquid and solid organic fertilizers).
- Tanks for storing digestate (lagoon).
- Checkpoint for the operational management of the biogas station.
- Laboratory for monitoring the characteristics of the substrate.
- Pumping station.
- Sanitary facilities for staff.
When designing and choosing equipment, it is always worth taking into account the type of raw materials used and the final goal (production of thermal energy for own needs or the production of electricity for sale). Ecodevelop specialists design a biogas complex depending on the needs and capabilities of each customer, taking into account the individual characteristics of raw materials and production.
Brief Process Description
The dry substrate is loaded into the module for weighing and feeding dry types of substrate. The liquid substrate is loaded into a special module. Further, the substrates are mixed and homogenized (brought into the most uniform state) for feeding directly into the fermenter.
In the fermenter, the preheated substrate is aged under anaerobic conditions for 20-35 days (this depends on the specific substrate). The generated biogas is accumulated in the gas tank mounted on the roof of the after-digester. The after-digester is necessary to increase the biogas yield from biomass by extending the exposure of the substrate to 50-80 days. Next, the spent substrate is separated by a separator into a liquid and a solid fraction and can be used as organic fertilizer.
Biogas from the gas tank is fed through a hydrogen sulfide removal and drying system to a cogenerator, where it is burned in a cogenerator burner to produce heat and electricity. A torch is also provided for burning excess gas or emergency discharge.
Electricity is distributed to the grid according to the “green” tariff, and heat is partially (up to 30%) used to heat the substrate at the entrance to the fermenter. The rest of the heat can be used to produce a coolant (heated water, superheated water or steam), and is used for the company’s own needs.
Biogas production as an economic and technical project
Ecodevelop, as one of the ukrainian market leaders in the bioenergy industry, offers professional services in creating renewable energy projects. We will not only design a biogas complex, but also help in choosing a site for construction, select the necessary equipment, help find additional financing, build the facility and bring it to the design targets.
Biogas production requires well-coordinated work of specialists of various profiles, from technologists and engineers to marketers and financiers.
Biogas provides independence from third-party energy sources, and also serves as a means of generating additional profit. Our task is to develop a business plan and create an effective energy production model that uses biogas – environmentally friendly and renewable raw materials.