Increasing Biogas Production With Biomass Briquettes

For example, activated carbon which has much more pores than ordinary charcoal, or one spoon of activated charcoal is estimated to have a surface area like the area of ​​a football field. With this surface area, activated carbon can adsorb much more molecules than ordinary charcoal. That is what makes activated carbon used by many industries, for more details, you can read it here. The activation process is the process of creating or opening the pores of charcoal so that it has a large surface area. Likewise with the biomass briquetting process, due to the strong pressure and high temperature of the briquetting process with a mechanical press, the micro pores of the biomass will open. The opening of the biomass pores will increase its absorption power. It turns out that according to research at Aarhus University Denmark, the use of biomass briquettes, especially straw briquettes, has been able to significantly increase biogas production. Every 1 tonne of straw briquettes added has increased the biogas production by an average of 400 cubic meters. With a biogas caloric value of around 4500 kcal / m3, each tonne of addition of straw briquettes will increase calories by 1,800,000 kcal in the form of biogas. Meanwhile, every 1 m3 of POME will produce about 25 m3 of biogas.

The research was conducted on a continous stirred tank reactor (CSTR) biogas type so that the effort to maximize the substrate mixture of biogas was carried out mechanically. CSTR for biogas production is still rare in Indonesia and the Southeast Asia region today, but is common in Europe. The addition of briquettes to the biogas reactor also means adding organic material as raw material for biogas production. But with this form of briquette which has the ability to absorb much more water or 10 times that of bulk straw without be briquetted, which causes microbes to penetrate far more through the micro pores of the straw briquettes, as a result the fermentation process is more perfect. Based on these experiments, the biogas production reached the optimum level at the addition of 10% straw briquettes to the reactor volume. The addition of straw briquettes of up to 10% apparently did not interfere with the performance of the stirrer motor and the straw briquettes because the micro pores absorbed water optimally and did not create floating material that covered the surface of the reactor. 

For biogas factories in Indonesia, especially Southeast Asia in general, especially those that use CSTR for biogas production, of course the above can be a reference and guide for trials to increase biogas production by adding biomass briquettes. In the above case, the straw used in Denmark uses straw from the wheat plant because it is abundantly available there, while in Indonesia and Southeast Asia, rice straw is widely available. The properties of wheat straw and rice straw are so similar that it is also predicted that they will produce almost the same volume of biogas. But if the biogas unit is for example in palm oil mills, biomass sources such as mesocarp fiber, empty bunches and palm leaves can be used as raw material for the briquettes. The biogas unit commonly used in palm oil mills in Indonesia and Southeast Asia using palm oil mill effluent as raw material is a covered lagoon which is not equipped with a mixer. For this type of reactor, one of the efforts to increase biogas production is by making the operating conditions thermophilic. The heat from the biogas power plant can be used to reach this temperature. Can biomass briquettes increase biogas production in covered lagoon reactors? The answer still needs further research.