Biogas & Energy
What is Biogas?
Biogas is a combustible gas that origins from digesting of biomass in anaerobic conditions. There is a difference between biogas and other combustible gases (e.g. natural gas). Biogas is only obtained from animal and vegetable organic raw materials. Biological waste, organic waste from food industry, energy crops such as corn or sugar beet and animal feces from stock farming can be used as a substrate in the biogas treatment plant.
The main process of treating biomass in the biogas plants can be described as follows independently from composition of the substrate used:
Biomass is decomposed by using bacteria and other microorganisms in the biogas plants. Final products of this multi-stage fermentation process are especially methane (45-70 %) and carbon dioxide (25-55 %) at anaerobic, free from light and humid environmental conditions.
Availability of using the biogas as an energy source mainly depends on methane content of the biogas. Produced biogas is usually transformed to electrical energy by combined heat and power plants (cogeneration) that can be directly used locally or can be supplied to the electric grid. It is also possible to use generated heat from combustion for heating of buildings near the facilities or greenhouses, drying hay, cooling milk or air-conditioning of stables. In order to be successful in terms of business economics, inclusively using obtained both products (electricity and heat) has great importance.
Another product is fermentation residues that can be used by operators as a high-quality agricultural fertilizer and can be sold. The advantage of fermentation residues compared to raw liquid and solid farm manure is nutrients can be absorbed easier by plants. Also liquid fertilizer obtained from biogas production is chemically less aggressive and generally odorless. What is more, disease-causing bacteria are largely disposed in the process of the biogas production.
Biogas can also contribute to energy security for the countries especially have energy deficit. Generated electricity and heat from the biogas plants contribute to the strengthening of decentralized energy infrastructure by preferably using a local scale. In addition, biogas plants provide employment opportunity at rural areas.
The energy produced from biogas compared to the energy produced from fossil energy sources, the degree of CO2 is neutral in principle: In other words, released CO2 is equal to CO2 that taken from atmosphere by plants before.
Anaerobic treatment can be shortly explained by decomposition of organic and inorganic matters by the help of microorganisms in the absence of oxygen and converting to final products such as CO2, CH4, H2S and NH3. First of all the anaerobic treatment began to be only used for sludge digestion. However, after becoming aware of advantages of compared to the aerobic treatment it has been started to be widely used for wastewater as well. Nowadays especially energy cost is an important problem, requiring less energy compared to aerobic treatment and even conversion of methane generated by the process to energy lead to use anaerobic treatment more widely.
The anaerobic treatment systems are used for stabilization of sludge formed from biological and physicochemical treatments, these methods are also used for treatment of industrial and domestic liquid waste contain or do not contain suspended solids. Decomposing of organic materials in wastewater at anaerobic conditions in the simplest term takes place in two main stages. In the first stage, conversion of organic matters to organic acids, alcohols and CO2 by acid bacteria (hydrolyze and acid fermentation) occurs. Second stage (methanogenesis) includes transforming of products resulting from decomposition reaction of acid bacteria into methane, CO2 and H2O by methanogens. Calorific value of methane resulting from these processes is high and methane can be used as an energy source.
Waste to Energy
Importance of alternative energy sources began to increase because of decreasing of fossil fuels it the world. In this context, both ensuring disposal of organic waste and the biogas plants which generate energy become popular day by day.
Treatment plant sludge, animal manure, organic waste, agricultural waste, plants such as corn or sugar beet, etc. are used as an organic waste.
In the biogas plants, anaerobic process contains decomposition of organic matters under anaerobic conditions which is also used for waste water treatment for many years is applied. Combustible biogas and fermentation residues (fertilizer) occur from decomposed organic substances as a result of this process.
Flow diagram of the biogas plant is shown below.
Produced biogas can be used for two purposes;
1- Heat energy can be produced by burning directly in a boiler.
2- Electrical energy and besides this heat energy can be produced by cogeneration (combined heat and energy plant).
It is possible to use heat generated additionally from cogeneration in burning process for heating of the building and greenhouses near the plants and air conditioning of farms.
In order to be successful in terms of business economics, inclusively using obtained both products (electricity and heat) has great importance.
In the biogas plants, also fermentation residues that can be used as high-qualified agricultural fertilizer occur. Generated fertilizer can be absorbed easier by plants, is chemically less aggressive and generally odorless. Furthermore, disease-causing bacteria are largely disposed in anaerobic process.
ARBIOGAZ applies anaerobic process in many years and builds biogas plants.
Sütaş Aksaray Factory – Wastewater Treatment Plant and Biogas Plant (total biogas production: 700 m3/ hour, 65 % methane)
Under the IPA Rural Development (IPARD) Programme approved by The European Commission, grant support is provided in order to promote agriculture and rural development for renewable energy. In this regard, you can get support to build biogas plant for renewable energy production for your plant.