The Roundtable on Sustainable Palm Oil (RSPO) is a non-profit association promoting sustainable palm oil through a voluntary certification scheme. Two successive science-based working groups on greenhouse gas (GHG) have been active in RSPO between 2009-2011, with the aim of identifying ways leading to meaningful and verifiable reduction of GHG emissions. One of the outputs is PalmGHG, a GHG calculator using the LCA approach to quantify the major sources of emission and sequestration for a mill and its supply base. A pilot study was carried out in 2011 on nine RSPO companies. Results gave an average of 1.03 t CO2e/t crude palm oil, with a wide range of -0.07 to +2.46 t CO2e/t CPO. Previous land use and area under peat were the main causes of the variation. Further modifications to PalmGHG are being made, notably to amend default values and upgrade it to a user-friendly software.