As an adsorbent, biomass activated carbon is effective at the removal of a wide range of organic and inorganic pollutants; however, its synthesis remains complex. Although spent coffee grounds (SCG) could be an effective material for the production of activated carbon, achieving a sufficient surface area has proven to be difficult. Here, this study presents a preliminary investigation into the optimal manufacturing conditions of activated-carbon adsorbents derived from SCG. SCG samples were characterized according to proximate analysis, elementary analysis, surface area, and pore volumes, then subjected to various processes (i.e., drying, carbonization, and chemical activation) with different operating parameters (temperature and time). The samples were optimized as follows: (1) Stable drying of SCG with a high moisture content of approximately 65% required consumption energy of 49 kWh/kg and drying at 105 °C for 20 h. (2) By comparing changes in the consumption energy and product yield with an increasing amount of carbon fraction, it was found that drying carbonization was more suitable than hydrothermal carbonization for SCG. The optimum drying carbonization temperature for achieving attractive biochar was 500 °C for 1 h. (3) Activated carbon with the optimum surface area (3687 m²/g) and mesopore volume fraction (approximately 70%) was achieved with a chemical activator agent ratio of approximately 3 and heating at 850 °C for 1 h. Furthermore, the butane working capacity of the activated carbon was related to the mesopore volume/surface area and reached 74.5% at a mesopore volume/surface area of 0.0004, indicating its suitability for activated carbon canisters. These findings can be used to optimize the synthesis of industrial-grade activated carbon from SCG.

Lithium–oxygen batteries (LOBs) offer the highest theoretical specific energy among metal–air chemistries, but their practical deployment is limited by the sluggish reversibility of Li₂O₂ formation/decomposition on the cathode, which requires a porous, electronically conductive carbon combining mesoporous transport with graphitic domains. Here, we report a two-step, KOH-assisted thermal treatment route for producing graphite-like porous carbon that converts spent mushroom substrate (SMS)—a lignin-rich agro-industrial waste generated at >5 million tonnes per year in East Asia—into a graphite-like porous carbon (G-SMS) for LOB cathodes. SMS derived from Pleurotus ostreatus cultivated on an oak–sawdust substrate was carbonized at 800 °C (1 h, 3 °C min⁻¹), followed by KOH-assisted heat treatment at 1200–1800 °C. A KOH/C ratio of 0.5 was selected for the detailed graphitization series for its reagent economy and carbon yield: the 1.0 ratio gave ~10 wt% lower production yield and, at 1800 °C, lower carbon content (97.6 wt%) with residual ash (1.7 wt%), for no compensating benefit. Within the KOH/C = 0.5 series, G-SMS-1800/0.5 combined the smallest interlayer spacing (d₀₀₂ = 0.347 nm), the lowest Raman I_D/I_G (0.69), the largest mesopore fraction (96.9%) and mesopore volume (0.31 cm³ g⁻¹), and the highest powder conductivity (8607 S m⁻¹ at 2000 kgf), giving the highest mesopore-volume-weighted conductivity descriptor of the matrix, V_Meso × σ = 2668 cm³ g⁻¹ S m⁻¹. This sample was identified as the most robust host, and its cycling stability was benchmarked against Super P in a modified CR2032 LOB cell (1 M LiTFSI in N,N-dimethylacetamide, 2.0 atm O₂): G-SMS-1800/0.5 sustained 330 cycles, whereas Super P reached only 200 cycles under identical conditions, a ~1.65-fold improvement. KOH-mediated catalytic graphitization thus lowers the thermal budget of biomass graphitization while providing a conductive, mesopore-dominated host for Li₂O₂ deposition, providing a potential route for the valorization of spent mushroom substrate into graphite-like porous carbon for LOB cathodes.

An integrated calculation combining X-ray fluorescence (XRF), thermogravimetric analysis (TGA), and elemental analysis (EA) was applied to the compositional assessment of commercial green silicon carbide (SiC) and biomass-derived synthesized SiC. Total carbon measured by EA and the mass loss assigned to free carbon by TGA were combined through the stoichiometric carbon fraction of SiC. The XRF inorganic elemental profile and the TGA mass gain, expressed as a free-Si equivalent, were used for a complementary component-balance calculation. Carbon-based SiC estimates were 99.1 and 99.4 wt.% for the commercial and synthesized materials, respectively, compared with KS L 1612 values of 99.7 and 98.6 wt.%. With hydrogen and nitrogen included and zero initial silica assumed, the component totals were 100.6 and 101.2 wt.%. The integrated approach couples carbon-based estimation with a balance check that exposes inconsistencies between thermal assignments and compositional inputs. This two-material application demonstrates the calculation and component-balance check under the stated assumptions; method precision and trueness require independent experimental validation.