Biogas Digester Factors in Plant Construction


Biogas digester produce biogas. This biogas is produced through anaerobic and aerobic digestion. These gases have 20MJ/Nm3 of heating value. This gases can be used for heating and electrical production produces. It is composed of gases and the most important is methane. Methane is very dangerous to environment when it is not burned. When it is released in the environment it causes global warming. All biomass when is decomposes produce gases that harms our atmosphere and etc. No doubt, having a biogas plant will surely save money and the environment as well. Biogas plants can either be aerobic or anaerobic production.


How does biogas work?

These gases are produced in a biogas digester. Inside this biogas digester are bacteria which literally eats the biomass. Then, gases are produce when there is something to digest. Bacteria inside the digester should be fed everyday with biomass waster and water. However, the biomass that is fed in the digester should be too much or too little or else it have adverse effects in these organisms. The digested biomass are turned into slurry the end product of the biomass digestion. Anaerobic production of biogas is the most productive way of producing gases, The slurry can be used as fertilizer for the plants. Next, the biogas produced can also be converted into power generation through conversion.

Aerobic vs Anaerobic Biogas Production

There are two kinds of processes in which biogas can be produced which is anaerobic or aerobic digestion. Anaerobic digestion is the production of gases in the absence of oxygen. Anaerobic production is usually used in biogas plant worldwide. However, aerobic digestion needs oxygen in order to produce gases. It is through anaerobic digestion that there is greater production of methane. Methane gases has caloritic value of 33.2-39.6 Joules/cm3. The methane production of aerobic biogas plants are quite small which makes them net energy consumer. Thus, makes the running cost of aerobic biogas plants expensive especially in the long run. However, Aerobic biogas production produces large quantity of sludge which is good for fertilizer. Finally, anaerobic production produces better output than aerobic biogas plants.



There are common four types of biogas plants:

  1. Fixed-dome plant

It is a fixed digester which has no movable parts. The gas production is quite simple in this design. The pressure of gas inside the digester increases as the volume also increase. This biogas digester is simple to make and low cost. It has a long use life which up to 30 years with proper maintenance. However, leaks must be avoided when construction. Leaks will cause in efficient in the biogas. Sooner or later this system will be useless. There are several examples of these designs such as Chinese fixed dome plant, Deenbandhu, Janata Model and CAMARTEC model.


  1. Floating drum plants

This biogas plant consists of a float drum and underground digester which makes gas detection easy. This drum is usually goes up and down depends on the amount of gas that is stored in the drum. Also, gas-holder floats either directly on gas production or in a water jacket of its own. Which makes the system easily understood by startups of this technology because of easy detection. However, this system is quite expensive because of the steel drum.


  1. Tube digester

This is a low cost model which used mostly in Bolivia, Peru, Ecuador, Colombia, Centro America and Mexico. Furthermore, the system can easily be set up by anyone there are many self help materials about this design. It can easily be integrate to your kitchen as substitute for LPG.


  1. Balloon Plants

The system can be easily understood by the investors. When the balloon bloats then there is gas that is present in the system. The balloon gas plant consists of a heat-sealed plastic or rubber bag, combining biogas digester and gas-holder. The pressure inside the balloon can be increased by placing weights on top of the balloon. However, technicians must assure that the balloon is fully seal and without leaks.

Factor affecting biogas production and construction

1.) Sub layer composition – In constructing a biogas plant it must be away from sources of detergents. These detergents kills the bacteria in the digesters. Also, inside the digester it must contain organic matter as feed stock in the digester. Inside the digester it must have a pH between 6.8 – 7.3 to produce quality gases.

2.) Temperature – The temperature inside the digester must be able to promote anaerobic digestion. This choice is critical in producing the amount and quality of gases to be produced. The micro –organisms present must be favorable especially the methanogenic organisms.

3.)Working Pressure– There must be a good hydrostatic pressure in the digester. Since, it increases the number of methanogenic bacteria per area. Which means with good pressure thus there is a good amount of biogas that will be produced.

4.) Budget in construction – You must consider which of the following types of biogas plant that you should you use. It must depend on the project amount of biogas you to produce. Is it economical? Will use this to produce electricity?

5.) Materials – Make sure to use materials that will last and will not contribute additional expenses in your production. When you keep replacing parts in your biogas plant it will sometimes be not feasible anymore.


There are three types of methanogenic organisms:

These methanogenic organims are cryophiles, mesophiles and thermophiles. Cryophilic organisms operate on temperature that ranges from 12 to 24°. Next, mesophilic organisms, operates between temperatures of 22-40° C. Finally,  thermophiles, operating at temperatures between 50 – 60° C which exhibit extreme tolerance in heat.


Biogas is for the Environment!

Biogas digesters are not complex at all. Farmers or even each household could use this untapped potential of biogas. Moreover, agriculture produces a lot of waste and these waster should be properly processed in order to beneficial. Directly putting it into the field as fertilizer and drying as energy source. Thus, it will limit the potentiality of the products you can get from your farm. On the other hand, being process first into biogas will help reduce the gases that is harmful to the environment. I hope you also differentiate aerobic and anaerobic production of gases. In times of climate change, we should shift a ourselves toward green energy and produce less carbon footprints. Others may say biogas plants don’t produce a enough energy but can just help the environment? Remember, farmers should take care of the environment for nature will reward us.