Carbon Inventory Assessment: A Strategy to Implement Nature-based Solution on Corporate Decarbonization Program of Balikpapan Refinery

Increasing national climate change commitments have driven corporations to adopt measurable decarbonization strategies, including nature-based solutions (NbS). This study aims to assess carbon stock within an existing corporate decarbonization program to support future emission reduction strategies. The research applied a mixed-method approach, including document review of biodiversity and Corporate Social Responsibility (CSR) programs, field-based biomass sampling in conservation areas, and carbon estimation using allometric equations. Field data were integrated with satellite-derived Normalized Difference Vegetation Index (NDVI) values and analyzed using simple linear regression to develop a predictive carbon stock model, followed by spatial mapping using raster analysis. The results indicate a strong relationship between NDVI and carbon stock, with a coefficient of determination (R²) of 0.706, suggesting that NDVI explains approximately 71% of carbon stock variability in the Balikpapan Refinery area. Total carbon stock within the conservation area was estimated at 311,968 tons, with CO₂-equivalent of carbon stock (tCO₂e) of 1,144,924.5 tons. CSR programs contributed an additional reduction of 18,359.77 tons CO₂, resulting in a total carbon absorption of 1,163,284.5 tons. These findings provide a robust baseline for corporate decarbonization planning and highlight the strategic importance of NbS in compensating for emissions from industrial operations.