*4.2. Rice Straw*

Rice straw consists of mainly lignocellulosic biomass with varying compositions of organic carbon. The electricity production can be carried out using this agricultural residue, with its hydrolysate being observed to be suitable to serve as a substrate. Comparatively, industrial wastewater has been recorded to generate maximum energy of 2.3 mW/m<sup>3</sup> , while achieving a 96.5% COD reduction; albeit, a pot MFC was used [82]. However, in the case of a carbohydrate-rich hydrolysate from rice straw in which 400 mg COD/L removal was observed, the recorded maximum energy output of 137 mW/m<sup>2</sup> was obtained. Still, when the conductivity of the solution was increased to about 17 mS/cm, about 293 mW/m<sup>2</sup> power density was reported [83]. In a two-chambered MFC to produce electricity without a pretreatment process, the powdered rice was applied directly to the anode side of the MFC in the presence of a mixed culture containing bacteria capable of breaking down the cellulose in the straw, culminating in a 54.3% increase in energy generation [76]. In other studies, the highest generated power was 190 W/m<sup>3</sup> when the utilized substrate underwent no pretreatment process; a mixed culture containing bacteria capable of breaking down cellulose in the MFC was used [92]. In this regard, MFC has shown a promising and convenient channel of treatment of wastewaters containing rice straw for the effective management of the wastewater to minimize pollution in the environment, which will simultaneously generate electricity.
