**2.1 What is bioelectricity?**

Bioelectricity is the electricity which can be generated from the biological sources and with the help of living materials [2]. Many times, the microorganism such as bacteria are the main working factors to generate electricity while biodegradable the organic waste both in the aerobic and anaerobic bacteria. The electroactive bacteria are most responsible for the electricity generation.

### **2.2 Organic waste composting**

Organic waste poses exceptional challenges during waste collection, particularly in hot and humid climates, where timely collection and disposal are critical. In some cities as much as 79% of municipal waste is organic [4]. Thus, organic waste management needs priority attention. The composting process which is the most common method for organic waste management, involves microorganisms feeding on organic material and consuming oxygen. The composting process generates heat, drives off moisture, and reduces bulky organic waste into a beneficial soil-like material containing nutrients, humus, and microorganisms in just a few months. Material in an unmanaged pile of organic debris will eventually break down but the process will take a long time and may result in odor or other nuisance problems due to poor aeration. Composting efforts may be easier to start if organic waste from food industry entities is used rather than household organic waste, because the quality of the organic inputs can be more closely controlled.

### **2.3 Biogas generation from organic waste**

Many researchers are trying to produce the biogas from different organic waste. The bacteria can decompose the organic waste and consequently generate the bio gas which are mainly methane and the carbon di oxide. The management of organic waste is a critical problem and biogas generation can be a solution of it, however, there are some socio-economic problems associated with the biogas production from the organic waste. The design of biogas plant in the urban area is a very difficult task due to the land requirements. Again, the use of biogas in the kitchen for cooking has not become popular among the users in the developing countries due to the misconception of the bad odour and aesthetic point of view [7, 8].

## **2.4 Laboratory experiments for microbial fuel cell**

One chamber MFC has been used for different types of organic wastes to generate bioelectricity. **Figure 1** illustrates the schematic diagram of the MFC which has been used in the laboratory experiment. Anode was embedded into the biomass while cathode was placed on the surface. The anode was set approximately 5 cm below the surface of the biomass, while the cathode was placed immediately above the biomass surface, but under the water.

The biomass used in the MFC were livestock waste such as cow dung, chicken droppings, rice waste, food waste and fruit waste. The basic properties of moisture content and organic content are listed in **Table 1**. It was noticed that the organic content of the different organic waste is not so much varied among them. It was also observed that the pH value of the initial condition of the different organic waste are within the range of 6.1–7.2 which was relatively suitable for the microorganisms working in the microbial fuel cell.

The design of the MFC was kept constant while changing the substrates inside the MFC as shown in **Figure 1**. The cylindrical shaped MFC chamber is 15 x 10 cm. The cross-section of the cell was 10 x10 cm. The electrode materials which were used in the MFC was carbon fiber, carbon felt for all the cases. The electrode amount was kept constant for all type of organic substances. The effective area of electrodes (anode and cathode) was kept the same as the cell areas (100 cm2 ).

The organic wastes such as cow dung was collected from the Department of Agriculture, Yamaguchi University at Yoshida campus, Japan while the chicken droppings, rice bran leaf were collected from Japan Agricultural Office, Ube city branch. The food waste and fruit waste were collected from the student's cafeteria of Yamaguchi University, Japan. In microbial fuel cell (MFC), bacteria used as biocatalyst to convert biodegradable organic substrates harmless by-products with the simultaneous production of electrical energy. The blended sample was poured into the container and placed the electrode and make the MFC. The external circuit was created by using the insulated copper wire connecting with an external resistor.

The voltage which generated across the resistor and capacitor was monitored every day at 1 pm by a multimeter. Polarization curve and power density–current curves were investigated by using different resistors and internal resistances and power densities were calculated as described elsewhere [8, 9]. Electrode output was measured in volts (V) against time. The current I in amperes (A) and power (P) was calculated using Ohm's law.

Statistical analysis was carried out and significant was taken when the p value was less than 0.05.

Experiments were conducted under a constant room temperature of 250 C [4].

**Figure 1.**



#### **Table 1.**

*Some basic properties of organic waste.*
