Data collection
The present study utilized a dataset, collected between 2001 and 2005 from the International Rice Research Institute (IRRI), in the Philippines, whereas the USA data were obtained from Arkansas University 2006/2007 (University of Arkansas 2006). All data used contained plot-level rice production information, such as machine, fuel, agrochemicals, farm yard manure, and human and animal labour use. For all major inputs into rice production, GHG emissions associated with these activities were calculated.