Forest carbon sink (FCS) is essential for achieving carbon neutrality and supporting sustainable development in ecologically fragile, resource-based cities such as those on the Loess Plateau. Despite the success of national afforestation programs, economic valuations of FCS at the city level remain limited. This study develops an integrated framework combining carbon stock estimation, regional carbon pricing, and net present value (NPV)-based valuation. Using Shenmu City in Shaanxi Province as a case study, forest carbon stocks from 2010 to 2023 are estimated based on the 2006 IPCC Guidelines. Future stocks (2024–2060) are projected using the GM (1,1) model. A dynamic pricing mechanism with a government-guaranteed floor price is applied under three offset scenarios (5%, 10%, 15%). The results show that Shenmu’s forest carbon stock could reach 20.67 million tonnes of CO₂ by 2060, and under a 15% offset scenario, the peak NPV reaches CNY 4.02 billion. Higher offset ratios increase FCS value by 18–22%, reflecting the growing scarcity of carbon credits. The pricing model improves market stability and investor confidence. This study provides a replicable approach for carbon sink valuation in semi-arid areas and offers policy insights aligned with SDG 13 (Climate Action) and SDG 15 (Life on Land).

Coal-dominated resource-based cities face a structurally embedded carbon-neutrality gap, shaped by the simultaneous pressures of industrial carbon lock-in and ecological fragility. China’s dual-carbon targets impose severe transition pressure on such regions, where carbon-intensive industries, strong path dependence, and limited decarbonization flexibility compound the challenge. Forest carbon sinks offer a cost-effective approach for offsetting residual emissions. However, water scarcity and restricted land-carrying capacity impose hard ecological ceilings on sink expansion in semi-arid areas such as the Loess Plateau. Existing studies have largely focused on national or provincial scales, with few addressing the coupled dynamics of industrial emissions and water-limited sink capacity at the county level. This study examines Shenmu, China’s largest coal-producing county-level city and a national energy-chemical industrial base. Using time-series data spanning 2010–2025, we project multi-scenario carbon emissions via an extended STIRPAT model with ridge regression, estimate forest carbon sink potential through a growing-stock (GS) gradient model cross-validated against GM(1,1), and systematically quantify the resulting carbon-neutrality gap. The results show that energy activities dominate total emissions throughout, consistently exceeding 90% of the aggregate. Under the baseline scenario, emissions reach 407.96 MtCO₂eq in 2060 without peaking; under moderate mitigation, emissions peak at 269.39 MtCO₂eq in 2050; under strengthened mitigation, emissions peak at 225.80 MtCO₂eq before 2040 and subsequently decline. Forest carbon sinks are projected to offset 2.1–11.2% of emissions by 2060 under all scenarios, constrained by climatic aridity, finite afforestation potential, and water–soil carrying capacity thresholds. The carbon-neutrality gap remains structurally positive across every scenario, reflecting a fundamental asymmetry between rigid emission growth and ecologically bounded sink capacity. These findings indicate that only an integrated pathway combining industrial restructuring, energy decarbonization, diversified ecological sinks, and CCUS deployment can substantially narrow the gap; carbon neutrality by 2060 is unattainable through natural sinks alone.