Seasonal Assessment of CH₄ and CO₂ Concentrations and IPCC Tier 1 Carbon Footprint Estimation in Benue State, Nigeria

Abstract

This study investigates greenhouse gas (GHG) emissions across diverse land-use types in Benue State, Nigeria, focusing on methane (CH₄) and carbon dioxide (CO₂) dynamics. Using calibrated gas detectors (MSA ALTAIR 4XR and PTM600-S) and meteorological instruments, weekly air samples were collected from 23 sites spanning agricultural, residential, commercial, and industrial zones between May and October 2025. Results show seasonal variability, with CH₄ concentrations ranging from 1.48–2.67 ppm and CO₂ from 415.3–498.2 ppm. Elevated CH₄ levels were observed in farmland and industrial areas, particularly during the wet season, while CO₂ concentrations peaked in industrial and residential zones, reflecting anthropogenic activities such as fuelwood use, transport, and industrial combustion. Multiple linear regression analysis revealed wind speed as a significant predictor of CH₄ variability (p < 0.05), with the model explaining approximately 27% of the observed variability (R² ≈ 0.27), whereas CO₂ concentrations were primarily driven by persistent emission sources rather than short-term meteorological conditions. IPCC Tier 1 emission estimates indicate that households contribute the largest share of Benue’s carbon footprint (260,000 kg CO₂e/year), followed by commercial transport (210,000 kg CO₂e/year), agriculture (222,500 kg CO₂e/year), and industries (150,000 kg CO₂e/year). Overall, the state’s partial carbon footprint was estimated at 842,500 kg CO₂e/year, based on selected activities rather than a complete statewide emission profile, with agriculture and households together accounting for over half of emissions. Although modest compared to Nigeria’s national inventory, these findings highlight Benue’s agrarian intensity and vulnerability to rising emissions. The study underscores the need for localized, data-driven mitigation strategies—such as improved biomass energy alternatives, sustainable rice cultivation practices, and industrial emission controls—to reduce GHG outputs and align with Nigeria’s broader climate commitments and global sustainability goals. However, the findings should be interpreted with limitations in mind related to the use of Tier 1 emission factors, the selected activity coverage, and the temporal scope of sampling.