*4.4. Vegetable Waste*

Vegetable waste can be regarded as another promising substrate that can generate energy from various MFC designs. It is usually generated during the washing and cutting of vegetables from various vegetable markets, restaurants, and some vegetable packaging industries. The electrogenic population in vegetable waste MFC tended to utilize the slurry form of the waste better during hydrolysis. In other studies, when the proportion of cooked and uncooked potato substrate was used in an MFC, increasing the coulombic yield culminated in 86.3% of COD removal (Du 2017; Du et al., 2018). An average current density of about 72.2–100.2 mA/m<sup>2</sup> was recorded, and 15.6–17.3% COD removal was achieved using vegetable waste containing effluent in combination with MFC; however, a diverse microbial consortium was needed, with some organisms such as *Firmicutes*, *Proteobacteria,* and *Geobacter* sp. proliferating in the anodic solution of the MFC. These organisms were the most dominant when using potato wastewater as a substrate, conferring the characteristics of suitable electrogens for electron transfer (Du, 2017). Moreover, a U-shaped MFC generated a current density of 314 mA/m<sup>2</sup> at a resistance of 123 ohms when a vegetable waste extract was applied as a substrate, demonstrating a higher power density output than the dual-chambered MFCs [95].
