Understanding the mechanism of KOH activation in the preparation of activated carbon (AC) enables more efficient utilization of biomass. In this study, brewer’s spent grains (BSGs) were carbonized at 500 °C to produce biochar (BC), followed by KOH activation under different activation conditions. The gas and solid products generated during the activation process were analyzed by gas chromatography (GC), X-ray diffraction (XRD), Raman analysis, a surface area and pore size analyzer, and X-ray photoelectron spectroscopy (XPS). The results show that increasing the KOH/BC ratio or the activation temperature could both promote gas production. XPS results indicated that the activator reacted first with -COOH and then with -OH of ACs, with AC_5-700 having the highest C-OH content (50.04%). As the KOH/BC ratio increased, more aromatic structures were destroyed, and the porosity of ACs was significantly enhanced, with AC_7-700 having the highest Brunauer–Emmett–Teller (BET) specific surface area (S_BET) (2997.69 m²/g). At low temperatures, KOH reacted with the active groups of BC and carbon at the edge of the aromatic structure. At high temperatures, the activator (KOH, K₂O, and K₂CO₃) reacted with carbon in the aromatic structure to generate a large number of pores on ACs and expand them. ACs exhibited more pores with higher KOH addition, and a higher activation temperature did not generate more new pores, but expanded the pores more significantly than high KOH addition.

Due to the exclusion of the tobacco industry from the mandatory compliance framework of the national carbon market, and the consequent absence of sustained policy-driven mechanisms and data verification systems, China has not yet established carbon emission calculation standards specifically tailored to cigarette factories. This study systematically reviewed mainstream domestic and international carbon accounting methodologies, analyzed emission sources specific to cigarette factories across Scope 1 to Scope 3, and developed corresponding calculation methods. Based on statistical data from field research at actual cigarette factories, a complete annual carbon emission covering Scopes 1-3 was calculated for a case-study factory. Considering data availability, internal controllability within the tobacco industry, and the guidance value for the sector's green and low-carbon transition, this study proposes recommended carbon emission calculation boundaries and itemized calculation methods for cigarette factories, aiming to promote the accuracy and standardization of carbon emission calculations in cigarette factories.