Valorisation of banana peel waste as a precursor material for different renewable energy systems

Highlights: • Banana peel waste (BPW) was subjected to different valorisation processes. • Low concentration of thermal NOx is generated by burning BPW after drying. • Biomethanisation of BPW produced 182 mL_STPCH₄/gVS and allowed removing 68% of waste. • A simple chemical activation and carbonisation process of BPW was demonstrated. • BPW showed good reversible capacity as anode for lithium-ion batteries (225 mAh/g). The following different valorisation processes of banana peel waste (BPW) were evaluated: combustion, production of activated carbon/batteries, and biomethanisation. This study showed that the combustion of BPW is an interesting option with a zero-carbon cycle. A mass balance demonstrated a low concentration of sulphurous compounds in the flue gases (0.01%, in volume), but the content of structural nitrogen dioxide was remarkable (0.35%). Additionally, BPW should be pre-dried to increase its lower calorific value (LCV) upto 3000 kcal/kg. In contrast, the mesophilic biomethanisation of BPW led to the generation of renewable methane (182 L_CH4/kg VS, volatile solids) and organic digestate, whereas its biodegradability was found to be 68% under the study conditions. The obtention of porous activated carbon was also demonstrated by employing a simple and low-cost method based on chemical activation/carbonisation of BPW with KOH porogen. The banana peel waste carbon (BPW–C) obtained showed low crystallinity, high purity, and Brunauer-Emmett-Teller surface area (S_BET) of 264 m²/g. BPW-C was tested as an anode electrode in lithium-ion batteries (LIBs), and a remarkable reversible capacity of 225 mAh/g at 0.2 C after 200 cycles was observed. These results indicate the feasibility of the carbonisation method of BPW to produce a highly demanded product in the current society.