Carbon footprint and greenhouse gas emissions of different rice-based cropping systems using LCA

There are many cropping systems adopted in floodplain soils but greenhouse gas (GHG) emissions balances of agricultural systems are rarely reported. Carbon (C) footprints of agricultural products were assessed using a co-designed life cycle assessment tool in major cropping systems in Bangladesh: rice-rice-rice (R-R-R/boro-aus-aman), rice-fallow-rice (R-F-R/boro-fallow-aman), maize-fallow-rice (M-F-R), wheat-mungbean-rice (W-MU-R), and potato-rice-fallow (P-R-F) along with the field measurement of some of the systems. The rice system with dryland crops had higher nitrous oxide (N2O) emissions (3.8 in maize, 4.5 in potato and 0.92 kg N2O-N ha-1 in mungbean) than sole rice (0.73 in boro, 0.57 in aus and 1.94 kg N2O-N ha-1 in aman) systems but methane (CH4) emissions were the opposite. Methane dominated the total emissions in rice accounting for 50-80%. The boro rice-based systems (R-R-R and R-F-R) had the highest C footprint (ca. 25.8 and 19.2 Mg CO2e ha-1) while the P-F-R (12.3 Mg CO2e ha-1) and M-F-R (12.6 Mg CO2e ha-1) had the lowest C footprint. Boro and aus were more suitable to reduce C footprint. Measured CH4 and N2O emissions agreed well with IPCC Tier 1 estimates, but they were available for boro, maize and wheat suggesting further study for validation and suitable GHG mitigation strategies.