Estimation of landfill design capacity using geometric footprint shape factors

The role of geometric landfill footprints in landfill planning stage is mostly unexplored. While there are precise on-site methods for waste volume estimation, the literature indicates a knowledge gap in developing a simple, data-efficient model for landfill waste capacity estimation in the pre-design stage where detailed engineering parameters are unavailable. This study addresses the gap by employing two quantitative shape factors (compactness and rectangularity) for closed landfill sites in Minnesota, United States. Geometric shape comparison revealed that the sites have a higher degree of rectangularity than compactness, with a median of 0.87 versus 0.69. Among the three waste footprint categories, the medium sized group shows the highest compactness value with a median of 0.82, followed by small (0.79) and large groups (0.76). The medium waste footprint has the highest rectangularity of 0.77, while the small waste footprints have a rectangularity of 0.74. A Pearson correlation test was conducted to assess the correlation of geometric footprint parameters with estimated waste volume. Surprisingly, the compactness and rectangularity of the landfill footprint are negatively correlated with waste volume with Pearson r values of -0.36 and -0.31, respectively (p-value <0.05). This may reflect the operational expansion patterns and regulatory constraints. The proposed regression model incorporating waste footprint area, landfill compactness, and age of the landfill showed reasonable explanatory power (R² = 0.682) with normally distributed residuals with Jarque-Bera statistic of 0.249, and p-value of 0.883. This model is intended for early-stage planning where detailed engineering parameters are not available. The findings suggest that landfill footprint compactness should be considered in early-stage landfill design assessment and landfill capacity planning.