Proper and innovative waste management methods still pose a major concern in our present world. Continuous accumulation of biowaste from bio-processing industries, household, organic residues and so on makes the environment polluted and endangers the health of man and other animals. The common waste management methods which include direct dumping into water bodies, open-air combustion, and as land fillers are obsolete and are the major causes of environmental pollution. Conversion of biowastes into valuable materials aids proper waste management, and helps to attain a cleaner environment, in addition to the fact that wastes are turned into wealth. Biowastes are rich in carbon and can serve as excellent precursors for the synthesis of important carbon materials such as activated carbon, graphene, carbon nanotubes etc. Three important methods of converting biowastes into carbon materials are discussed in this review. The electrochemical, adsorption, and electrocatalytic properties of the materials and the applications in electrochemical energy storage devices are also discussed in brief. This review focuses on the synthesis of carbon materials from biowaste residues and their use in developing electrode materials for batteries and supercapacitors. Future perspectives on the need to exploit greener technology for the conversion of biowastes into important carbon materials should be considered.

Composite materials based on polyaniline and graphite were prepared using in situ polymerization of an aniline monomer without any previous treatment. Three monomer/graphite weight ratios during polymerization were studied, which were 1:1, 1:2, and 1:3. The composite materials showed a nanochain-like structure whose dimensions vary with the graphite content. Materials were deposited over a fluorine-doped tin oxide (FTO) substrate to evaluate its capacitive performance. The electrochemical measurements carried out in a 0.1 M aqueous solution of H₂SO₄ showed that PANI-Gr1 composite electrode exhibits a capacitance of 238 F·g⁻¹ at 0.5 A·g⁻¹ within a potential window of 0–0.6 V vs. Ag/AgCl. At a current density of 4.0 A·g⁻¹, the PANI-Gr1 composite shows an energy density of 3.0 Wh·kg⁻¹ that is 30% higher than pure PANI, results due to an increase in electrical conductivity concomitant with the morphology change and surface area increase. Composite materials showed promising properties as easily processable and scalable electrodes for supercapacitors.