Microbial Fuel Cell Reactor from Liquid-Waste tofu generates electricity

Clean energy has been becoming intriguing factors in the last two-three decades. One of the factors is the greenhouse effect which can create the global warming. Others suggest that because we are running out of fossil fuels. The demands of another energy resources are growing astronomically. To answer it, scientists in several world has come with bioenergy and one of it is from liquid-waste tofu.

The pulp and liquid-waste of tofu is generated from tofu manufacturing
(image is credited by https://media.treehugger.com)

Tofu is one of the popular food among Indonesian. It has been considering by many ethnicities in Indonesia used tofu for their daily consumption. There are so many traditional culinary that use tofu as their main ingredient such as Kupat Tahu, Karedok, Gado Gado and many snacks which use that also.

Tofu is manufactured from soybean and it is coagulated for nights. The production has been increasing from micro-production to macro-production and as the result generates two wastes which are liquid and pulp. On the other hand, because the liquid-waste generating from manufacturing is high, the demands of water in making tofu is high too. This gives big impact to the environment so in addition to prevent the damage, scientists take advantage from the chemical components of the waste by turning it into bioenergy throughout microbial fuel cell reactors that can generate electricity.

Microbial fuel cell system in producing electricity from tofu

In producing the electricity, the normal reactor must be filled by the required chemical substance which are flammable and volatile to create electricity from the machinery. But, in microbial fuel cell (MFC) system, the difference is only located on the source of the electron. In normal machine, the source of the electron is generated by the converting process of heat energy to move the electric motor. In the contrary, the source of electron in microbial fuel cell is processed from the oxidation of organic compounds created by the microorganisms (Watanabe, 2008). So, when the electron arrives on the anode of the MFC, it will be delivered directly to cathode as the difference of potential between two metals and this lead to oxidation process in forming water (Mathuriya & Sharma, 2010).

In short, we need to things which are the agent oxidation and the bridge to connect the electron. As the agent, we used biological living things or microorganisms such as Geobacter sulfurreducens (Trinh, Park, & Kim, 2009) and Lactobacillus bulgaricus (Inayati, Aminin, & Suyati, 2015). As we know that one of the bridge in connecting the electron is the substrate which is similar like we do in electrochemical process. Therefore, electrolyte solution is required and the required solution is processed by the microorganism by creating the acid solution. Consequently, the electrolyte solutions have to be solutions that can be medium for growing the microorganisms.

In processing tofu, the demand of water is high so the results of the waste are pulp and liquid. These two wastes are potentially to be utilized because of containing compounds of glucose within it. Therefore, the amount of glucose is used by the bacteria as the main source of food and the results is the converting process into acid or electrolyte solutions.

The electron can be moving because of the salt bridge
(image is credited by https://chemistry.stackexchange.com)

In addition to make it connected, the use of salt bridge in important. But chemically speaking, the salt bridge here is used so the electron could be in balancing system as the electrons is always moving to find the lowest potential. This moving which flows from one cell to another cell creates electricity or bioelectricity.

Tofu liquid-waste as the bioelectricity source

The liquid-waste of manufacturing tofu creates the source of glucose for the microorganisms into acid solutions. This bio-chemical process is occurred in process of oxidation of the glucose creating the free electrons. By transferring the electrons, it can produce electricity. However, the bioelectricity that is produced from this anaerob reactor generates little voltage around 30 to 60 mV (Ismawati, Aminin, & Suyati, 2015).

References
[1] Inayati, N. S., Aminin, A. L., & Suyati, L. (2015). The bioelectricity of tofu whey in microbial fuel cell system with Lactobacillus bulgaricus. Jurnal Sains dan Matematika, 32-38.
[2] Ismawati, N., Aminin, A. L., & Suyati, L. (2015). Whey Tahu sebagai penghasil bioelektrisitas pada sistem microbial fuel cell dengan Lactobacillus Plantarum. Jurnal Sains dan Matematika, 43-49.
[3] Mathuriya, A. S., & Sharma, V. N. (2010). Bioelectricity production from various wastewaters through microbial fuel cell technology. Journal of Biochemical Technology, 133-137.
[4] Trinh, N., Park, J., & Kim, B. (2009). Increased generation of electricity in a microbial fuel cell using Geobacter sulfurreducens. Korean Journal of Chemical Engineering, 748-753.
Watanabe, K. (2008). Recent developments in microbial fuel cell technologies for sustainable bioenergy. Journal of Bioscience and Bioengineering, 528-536.