Rice contributes significantly to greenhouse gas (GHG) emissions from the food system. Previous studies mainly focused on emission reduction methods within the rice farming system rather than examining systematic solu-tions along the rice value chain. Organic and rice -fish co-culture rice are considered promising solutions for re-ducing environmental burdens. This study compared the GHG emissions of organic, rice -fish co-culture, and conventional rice value chains (including cultivation, processing, transportation, cooking, and waste disposal) with a cradle-to-grave system boundary and a new perspective from consumer dietary habits changes. The re-sults indicated that organic rice had the highest carbon input, output, and net GHG emissions in the farming sys-tem, with 9.277, 9.658, and 0.380 kg CO2-eq kg-1 white rice, respectively. However, the net GHG emissions from rice -fish co-culture and conventional rice farming systems were -1.682 and -0.393 kg CO2-eq kg-1 white rice, respectively. Methane (CH4) contributed more than 60 % of the total GHG emissions of the three rice farming sys-tems. Post-harvest systems, including processing, waste disposal, and transportation, contributed little to the GHG emissions of the three rice value chains. The cooking system was a relatively primary source of GHG emis-sions due to electricity consumption. Concerning the whole rice value chain, though higher consumption sustain -ability levels were assumed for the organic rice and rice -fish co-culture value chains, they were still carbon sources with GHG emissions of 0.770 and 0.147 kg CO2-eq kg-1 white rice mainly from the farming system, while the conventional rice value chain was a carbon sink (-1.012 CO2-eq kg-1). The results are similar to the functional unit of the capital diet. In this case study, organic rice had higher GHG emissions than rice -fish co -culture and conventional rice along the rice value chain, mainly from the farming system due to higher organic material inputs. Future studies should focus on reducing CH4 emissions from organic rice cultivation through sustainable soil and water management. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.