Reflective Landfills: High Albedo Surfaces as a Pathway for CO2 Compensation

Increasing surface albedo can reduce absorbed solar radiation and generate negative radiative forcing, but its application to landfill covers remains insufficiently investigated. This study assessed the potential climate benefit of reflective cover systems at the Malagrotta landfill in Rome, Italy, by integrating unmanned aerial vehicle (UAV) radiometry, Sentinel-2 imagery, shortwave-radiation modeling, and CO2-equivalence methods. The existing landfill exhibited low and heterogeneous reflectance. Quality-controlled Sentinel-2 observations produced seasonal mean albedos ranging from 0.0819 in winter to 0.1236 in summer, with a radiation-weighted baseline albedo of 0.1091. UAV campaign means ranged from 0.1391 to 0.2145. Comparisons over common 20 m cells showed that Sentinel-2 underestimated UAV albedo by approximately 0.087 on average (RMSE ≈ 0.093), demonstrating that the two platforms should not be considered interchangeable without site-specific calibration. Five hypothetical reflective-cover scenarios with albedos of 0.55–0.75 were subsequently evaluated. Relative to the existing surface, annual absorbed shortwave energy decreased from 1481.1 kWh m−2 to 748.1–415.6 kWh m−2, equivalent to reductions of 49.5–71.9%. After accounting for modeled atmospheric transmission, avoided absorbed energy at the top of the atmosphere ranged from 487.4 to 708.9 kWh m−2 yr−1. Under a three-year material service life, the modeled compensation was 71.49–103.98 kg CO2-eq m−2 over a three-year assessment horizon. Alternative literature-based conversion methods yielded landfill-scale estimates of approximately 31,700–142,000 tCO2-eq, highlighting substantial methodological uncertainty. The findings indicate that reflective landfill covers could provide a meaningful supplementary climate benefit on low-albedo, centrally managed surfaces. However, the results are scenario-based and represent radiative equivalence rather than physical CO2 removal or avoided methane emissions. Field trials, multiyear monitoring, complete surface-energy-balance measurements, and cradle-to-grave life-cycle assessment are required before operational deployment or carbon-offset applications.