Carbon footprint of oil palm planted on peat in Malaysia

The carbon footprint of palm oil on mineral soils based on primary data from Malaysia was published in 2011, but a study for palm oil grown on peat is missing. The estimation of greenhouse gas emissions (GHG) of oil palm planted on peat in Malaysia was divided into three main components, namely GHG emissions from land use change, peat oxidation due to the establishment of oil palm plantations, and operations during cultivation and milling processes. The study collected comprehensive primary data for the latter and derived a best estimate for the other emissions to provide guidance for the most appropriate values and uncertainty range for oil palm planted on peat. The study highlights uncertainties and gaps in knowledge and provides recommendations for reducing GHG emissions for oil palm planted on peat.

GHG emissions were estimated based on published data (LUC and peat oxidation) as well as from comprehensive primary data from operations at plantations mainly on peat in Sarawak and the palm oil mills for the period of 3 years. For this study, the data is partitioned into three case scenarios: (a) base case, where oil palm plantation is assumed from previously logged-over (PSF) with medium level of peat oxidation and 50% of the mills have the facilities to capture methane; (b) best-case scenario, where oil palm is assumed planted from previously degraded PSF or land with lowest estimation of peat oxidation and mills with methane capture facilities; and (c) worst-case scenario, where oil palm is assumed planted from previously virgin PSF with the highest estimation of peat oxidation and mills with methane capture facilities. GHG emissions from cultivation and milling stage were modeled using the System for Integrated Environmental Assessment of Product (SimaPro, version 8) with Ecoinvent database (ver 3).

Total GHG emissions for oil palm planted on peat for three scenarios arising from three main components range from 12.4 t CO₂ eq ha⁻¹ (best case) to 76.6 t CO₂ eq ha⁻¹ (worst case). These variations depend on C stock of previous vegetation, depth of drainage, length of time of drainage, amount of nitrogen fertilizer used, and use of methane capture facilities at the palm oil mills.

GHG emissions for oil palm planted on peat can be reduced by developing plantations from degraded PSF or grassland with low carbon stock, with effective water management coupled with methane capture facilities at the mill and judicious application of nitrogen fertilizers using precision application according to requirement of the site based on diagnosis of nutrient requirement from soils and foliar analyses. In Malaysia, only 13% of the areas planted with oil palm are on the peat soil. Therefore, the overall GHG emission at the national level (13% planted on peat and 87% on mineral soils) can be further reduced by around 4.1 t CO₂ eq ha⁻¹ year⁻¹.