Carbon footprint assessment of natural rubber derived from Liberian hevea trees

The purpose of the study is to analyze current hevea farming practices and block rubber manufacturing in Liberia and estimate their carbon footprint. A cradle to gate life cycle assessment was performed on hevea rubber produced in Liberia. Primary activity data was collected from farmers and rubber mills and used to validate an engineering process model which was coupled with life cycle inventory data to perform a life cycle assessment. The modeling work includes alternative farming scenarios. Results show that 1 kg of block rubber (99% dry rubber content) is responsible for 0.39 kg CO₂e. The majority of the emissions, 0.27 kg CO₂e/kg, come from the farming stage with the rest, 0.12 kg CO₂e/kg, produced during the manufacturing phase. At the farm gate, fertilizer use first, and diesel use second, are the highest contributors to the carbon footprint. The studied system derives electricity from local hydro resource and thus electrical consumption in manufacture has minimal impact to total greenhouse gases. The highest contributor in processing the feedstock to rubber is diesel used to run machinery and a back-up electricity generator. Biochar production from hevea trees at end of life showed the ability of greatly reduce the carbon footprint, making the entire system a carbon sink. Conversely, forest clear-cutting to plant hevea trees had a large impact on the product carbon footprint highlighting the importance of accounting for these practices in future assessments. GHG emissions described for Liberian rubber were lower than those of other geographical areas (Southeast Asia), and other rubber alternatives (guayule, dandelion, and synthetic).