Supercapacitors Made From Banana Peels and Chicken Bones Could Power the Green Grid

Global energy consumption has exploded from roughly 12,000 terawatt-hours in 1900 to nearly 186,383 terawatt-hours in 2024, according to the International Energy Agency, and the way we store all that energy is under intense scrutiny. While the share of clean energy in the global portfolio has surged from 25 percent in 2014 to 71 percent in 2023, renewable sources such as solar and wind remain stubbornly intermittent. The missing piece of the puzzle is not generation but storage, and one of the most promising candidates is a device that can charge in seconds, survive millions of cycles, and now, remarkably, be built from agricultural waste, fruit peels, algae, and even cooked chicken bones. A comprehensive new review published in Advances in Industrial and Engineering Chemistry by Dhananjaya Merum and Misook Kang of Yeungnam University maps out how biomass-derived carbons are poised to transform supercapacitor technology from a laboratory curiosity into a cornerstone of sustainable energy infrastructure.

Supercapacitors occupy a unique niche on the energy storage landscape, bridging the gap between traditional capacitors and rechargeable batteries. Where batteries excel at storing large amounts of energy for long durations, supercapacitors deliver exceptional power density, ultrafast charge-discharge kinetics, and an operational temperature range spanning from minus 40 to 85 degrees Celsius. Unlike conventional batteries, they can endure millions of charge-discharge cycles with minimal degradation, making them exceptionally reliable for high-frequency applications. On a Ragone plot, which maps the trade-off between energy density and power density, supercapacitors sit firmly in the high-power regime. This makes them ideal for regenerative braking in electric buses and rail transit, frequency regulation in smart grids, short-term buffering in solar and wind installations, and rapid-charging support in smartphones and wearable electronics. Hybrid systems that pair supercapacitors with batteries are already optimizing energy management in electric vehicles, aerospace platforms, and portable medical devices.

The problem with conventional supercapacitor electrodes is their pedigree. Activated carbon, the workhorse material, is typically derived from coal tar, petroleum pitch, or synthetic polymers, tying an ostensibly green technology directly to fossil fuel extraction. Graphene and carbon nanotubes offer superior conductivity and mechanical integrity, but their large-scale synthesis remains energy-intensive and costly. Worse still, the processing and disposal of materials containing fluorine, sulfur, cyanide groups, or heavy metals carry significant environmental burdens. The review argues that advancing sustainable electrode materials is not merely a scientific challenge but an environmental imperative, and this is precisely where biomass-derived carbons enter the picture, offering a renewable, low-cost, and carbon-neutral alternative that can be engineered with remarkable precision.

The chemistry underlying this transformation is elegant. Lignocellulosic biomass, the structural material of plants, is composed of three biopolymers whose thermal behavior dictates the final carbon architecture. Cellulose, a linear polymer of glucose units making up 35 to 50 percent of the material, decomposes between 260 and 350 degrees Celsius, releasing volatile species such as carbon dioxide, carbon monoxide, methane, and water vapor that carve out micropores in an amorphous carbon framework. Hemicellulose, a branched heteropolymer rich in acetyl and hydroxyl groups, breaks down even earlier, between 180 and 260 degrees Celsius, promoting micropore formation and oxygen doping. Lignin, an aromatic biopolymer, decomposes gradually over 200 to 500 degrees Celsius, condensing into graphitic domains that improve electrical conductivity and mechanical stability. The coexistence of these three components yields hierarchically porous carbon networks combining micropores smaller than two nanometers, mesopores between two and fifty nanometers, and macropores larger than fifty nanometers, a structure that facilitates both electrolyte accessibility and rapid ion transport.

Beyond porosity, biomass brings a built-in doping chemistry that conventional precursors cannot match. Algal biomass, rich in proteins and amino acids, introduces nitrogen in pyridinic, pyrrolic, and graphitic configurations, along with sulfur dopants, all of which enhance redox activity and conductivity. Food waste contributes phosphorus species that expand interlayer spacing and improve surface polarity and wettability. Even the inorganic constituents play a role: potassium carbonate and calcium carbonate act as in-situ activation catalysts through carbothermal reduction reactions, while silica species provide rigid templates that define mesoporous channels before being washed away. The numbers emerging from this approach are striking. A nitrogen-doped hierarchical porous carbon reported in the review achieved an ultrahigh specific surface area of 3,142 square meters per gram and an energy density of 88 watt-hours per kilogram with only 9 percent capacitance loss over 10,000 cycles. A nitrogen-phosphorus-sulfur co-doped carbon derived from peanut meal delivered a specific capacitance of 525 farads per gram, retaining 68 percent of that value even at ten times higher current density.

Synthesis routes matter enormously, and the review dissects them with technical rigor. Pyrolysis, heating biomass in an oxygen-free atmosphere at 300 to 1,200 degrees Celsius, promotes graphitization and conductivity at high temperatures while preserving oxygen-containing functional groups that improve wettability at lower temperatures. Hydrothermal carbonization, which treats biomass in water under high pressure, offers a greener, lower-temperature route that retains oxygen functionalities, making it suitable for flexible, binder-free, solid-state devices. In one standout example, researchers combined hydrothermal carbonization with chemical activation to create a 3D-printed electrode from poplar sawdust that mimicked wood’s vascular patterns, achieving a specific surface area of 253 square meters per gram and an areal capacitance of 7.95 farads per square centimeter at a mass loading of 17 milligrams per square centimeter. Activation, whether physical using steam or carbon dioxide, or chemical using potassium hydroxide, zinc chloride, or phosphoric acid, remains the decisive step for unlocking high surface areas, though the review notes that corrosive chemical activation poses environmental concerns of its own.

Some of the most creative work dispenses with external chemicals entirely through self-activation and bio-inspired templating. Platycladus orientalis leaves were converted in a single step into nitrogen-oxygen-sulfur co-doped hierarchical porous carbon, with the plant’s own bioactive elements driving simultaneous carbonization, doping, and pore formation. Transgenic technology has even entered the field: researchers regulated the SlHDA3 gene in tomato stems to modify their cellular structure before carbonization, yielding a material that achieved a specific capacitance of 201.6 farads per gram and an energy density of 11 watt-hours per kilogram in a symmetric device. A spider web-inspired three-dimensional carbon network built on metal-organic framework templates reached 395 farads per gram and successfully powered 19 red LED lights. Meanwhile, hydrogen-bonded organic framework templates converted heavy bio-oil into flower-like carbon architectures delivering 117.5 watt-hours per kilogram in zinc-ion hybrid supercapacitors, and ice-templating produced hollow carbon cages with hierarchical porosity for the same application.

The waste-to-wealth case studies read like a catalog of unlikely hero materials. Cooked chicken bones, activated to an ultrahigh surface area of 2,235.8 square meters per gram, delivered a capacitance of 329.41 farads per gram with 99.8 percent coulombic efficiency and 90.1 percent retention after 20,000 cycles. Chicken fat oil was transformed into multilayered graphitic carbon nano-onions via simple flame pyrolysis, and sulfur-nitrogen doping pushed their capacitance to 261 farads per gram, enabling an asymmetric device with 32.8 watt-hours per kilogram energy density. A dual-precursor strategy combining hydrochar with polymerized bio-tar produced an interconnected mesoporous network with a surface area of 2,714 square meters per gram and 88.6 percent retention after 5,000 cycles. Daylily, an edible herb, yielded nitrogen-phosphorus co-doped carbons with 299.1 farads per gram and 99.6 percent retention after 4,000 cycles. Even human hair has found a role as a conductive scaffold, supporting silver and nickel-doped manganese oxide composites that reached 1,770 farads per gram in a hybrid supercapacitor.

Hybridization with pseudocapacitive materials represents perhaps the most powerful design strategy, bridging the gap between battery-like energy and capacitor-like power. A nickel-cobalt layered double hydroxide heterostructure anchored on pomelo peel-derived porous carbon delivered an extraordinary 3,290 farads per gram, and the assembled asymmetric device achieved 51 watt-hours per kilogram with a peak power density of 16 kilowatts per kilogram. Biomass-derived carbon nanosheets encapsulating iron oxide nanoparticles retained 99.6 percent of their capacitance after 100,000 cycles, with a redox additive doubling the energy density to 32 watt-hours per kilogram. Aloe vera gel served as a natural reducing agent for green synthesis of cobalt oxide nanostructures, eliminating toxic chemicals while achieving 468 farads per gram. These results demonstrate that biomass-derived carbons function not merely as cheap substitutes but as sophisticated conductive scaffolds that buffer structural strain, facilitate charge transport, and enable rapid ion diffusion in next-generation composite electrodes.

Significant hurdles remain before banana peels and bone ash power our grids. Feedstock variability leads to inconsistent carbon yields and electrochemical performance, making process standardization difficult. Chemical activation demands high energy input and generates hazardous by-products, and achieving uniform pore size distribution and precise dopant control across batches is still elusive. Flexible and wearable applications require freestanding films rather than binder-bound powders. The review’s authors propose a clear roadmap: scalable continuous processing integrated into existing agro-industrial supply chains such as rice mills and sugar refineries, green activation methods, standardized performance metrics, life-cycle and techno-economic assessments, and prototype-scale validation. If those pieces fall into place, biomass-derived carbons could deliver a rare double win in the energy transition, simultaneously diverting waste from landfills and storing the renewable electricity that will replace fossil fuels, one charge at a time.

Subject of Research: Biomass-derived carbon materials for sustainable supercapacitor electrodes

Article Title: From biomass to energy storage: sustainable carbon materials for next-generation supercapacitors

Article References: Merum, D., & Kang, M. (2025). From biomass to energy storage: sustainable carbon materials for next-generation supercapacitors. Advances in Industrial and Engineering Chemistry, 1(1), Article 26. https://doi.org/10.1007/s44405-025-00028-7

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00028-7

Keywords: supercapacitors, biomass-derived carbon, activated carbon, heteroatom doping, pyrolysis, hydrothermal carbonization, porous materials, energy storage, waste valorization, circular economy, electric double-layer capacitor, renewable energy