THE BIOGAS PROCESS

The Biogas Process

 

Dear Visitor,

Biogas is an anaerobe digestion process of micro-organisms and it is one of the oldest processes in the world and based on nature itself. Therefore NATURE is the best TEACHER to realize and operate the most efficient process.

Now, many biogas plants all over the world - including in Germany - do not really "copy" and "industrialize" nature in its most efficient way. The reason for that is the human arrogance to think that we are better than nature - or the human greed not to spend the money necessary to realize a system, which was developed over millions of years by nature. This behaviour result in a wide variety of biogas processes and technologies - which have all their places in human economy. The selection - however - depends on the business case, the business philosophy and for sure the local available organic material. therefore the first and key question is:

What is the Intention: Waste Reduction - OR - Maximized Biogas & Power Production ?

Depending on this first answer and decision, the whole biogas project and process selection will be totally different.

 

 

Nature is the Teacher

As a nearly perfect example for natural biogas production under controlled and optimized conditions the stomach of cattle and similar animals can be mentioned. To make the nutrition available in grass and leaves, the stomach utilizes the microbiology which in the end also produces methane gas. It is today well known that cattle produce a significant amount of methane inside their digestive system.

The stomach of cattle but also other animals feeding on cellulosic, fibrous material like grass, straw and leaves has 4 chambers which create a perfect environment for each group of microbes. These microbes are breaking down the cellulosic material and make the nutrition available. In addition, hemicellulose will be broken down into starch and sugar molecules. Further on the process produces the organic acids and finally methane - which is only a final by-product in the digestive system and not the target.

Having understood this system, we should simply "copy" the stomach of such animal with the four chambers, controlled temperature and humidity and we would have highest performing biogas production. However, economical reasons have a strong impact on "streamlining" the process into one compartment (can be several tanks) which contains all four microbes. Therefore the conditions are not according nature and it is self understanding that the performance is much lower than potentially possible.

Also here, nature has some examples, which operate under difficult or nearly impossible conditions but due to the factor of time, the process is working and transforming organic material while producing methane gas. Such natural slow and low performing processes (under aspect of time !) are swamps, methane lakes and deep see always with low or no oxygen and darkness. Therefore, a pure approach of organic waste reduction can be done under similar conditions with very low costs but it requires a long processing time (retention time). Typical applications are given with large anaerobe lagoons as well as with landfill biogas.

 

 

 

Anaerobe Biochemistry - a short Glimpse

The natural occurring microbes, which produce in a symbiosis finally methane gas are available nearly everywhere on our world. For sure, meanwhile there are genetically enhanced microbes as well as there are different types and families with some different conditions, however, the process basics are similar.

 

 

Such are the basic processes but the challenge is given in the different conditions, the microbes need to work with high performance as explained above. The stomach of cattle and similar animals are designed to extract maximum nutrition out of their fodder. Therefore the stomach offers nearly perfect conditions for each group of microbes: Temperature, Feeding, Moisture and pH Value. Compared to a swamp, methane lake or landfill with anaerobe process, there are all microbes mixed up and work under nearly similar conditions. Over significant longer time, the same result will be reached compared to the stomach of cattle - except, fibrous material need additional organisms like mushrooms and weaves to break down the cellulosic fibrous material into digestible starch and sugar molecules.

 

The Methane Reaction

The final methane production is based on conversion of organic acids into methane and carbon dioxide. The higher organic acids like propionic acid (propionic acid) and butter acid will be converted into acetic acid and hydrogen. Acetic acid will be converted into methane gas and carbon dioxide in the final step of the methanogenesis. The hydrogen produced has a major role in the process stability as well as for the pH level and an additional reaction, which will increase the methane level significantly. In such reaction hydrogen react with carbon dioxide and produce methane and oxygen.

 

 

 


The so called hydrogen balance is a sensible but very efficient system to evaluate the process efficiency and performance. therefore the hydrogen is a major parameter for any biogas plant and to understand the status of process conversion efficiency.

 

Result and Summary

 It is "very easy" to start and operate an anaerobe process as it is one of the most established natural processes to recycle organic digestible material back into the natural cycle. The real challenge is to reach industrial performance levels as well as to operate the biogas plant according to the needs and requirements of the microbes. Therefore, all processes available today will produce biogas and methane - but with a wide range in performance, feedstock utilization, organic conversion efficiency and scale of the plant. The above Key Decision - in regards to organic waste reduction OR biogas fuel and power production - will influence the process selection and budget tremendously. 

Whatever philosophy, decision and process was selected, one most important issue need absolute attention: A Biogas Plant IS a LIVESTOCK Farm with several different organisms as other animals we are cultivating and serve our purpose. Therefore, we should understand to treat these organisms in the right way and for the purpose to enrich our live and increase our living standards.