Carbon footprint assessment of rice-frog coculture system

Objective The carbon footprint of rice-frog ecological breeding model was systematically studied in order to provide scientific basis and optimization suggestions for the sustainable development of this model.

Method The carbon footprints of traditional rice monoculture (TR), green rice-frog coculture (GF) and organic rice-frog coculture (OF) modes were evaluated by life cycle assessment.

Result The carbon footprints per unit area of GF and OF were 5985.2 and 5632.99 kg CO₂e·hm⁻², which reduced by 5.98% and 11.51% compared with TR, the carbon footprints per unit profit decreased by 45.10% and 45.87%, and the carbon footprints per unit nutrient density decreased by 14.63% and 12.17%, respectively. GF and OF increased the net ecosystem economic benefits by above 50%, with 71.77% in GF. Compared with TR, the production of GF had no significant difference, while that of OF decreased by 16.73%. The CH₄ emission increased by 58.13% and 131.18%, and the N₂O emission decreased by 41.06% and 63.12% respectively. GF and OF had higher global warming potential and greenhouse gas emission intensity, among which the effect of OF was more significant. In GF and OF, the input of organic materials such as milk vetch, rapeseed cake and organic fertilizer showed net carbon fixation effect. The carbon footprint composition and sensitivity analysis showed that greenhouse gas emission (57.07%) and fertilizer application (32.88%) accounted for the highest carbon footprint composition of TR. The carbon emission and fixation of OF were higher than those of GF, and the CH₄ emission and use of nylon protective net contributed the most to GF and OF. Uncertainty analysis showed that the carbon footprints per unit area of GF and OF were 5907.29 and 5647.25 kg CO₂e·hm⁻², respectively, which was lower than that of TR, and the coefficient of variation was less than 7.5%.

Conclusion The rice-frog coculture modes (GF and OF) show a more significant carbon fixation and environment friendliness than TR mode, and provide a new scientific basis for green and low carbon development of rice industry in our country under the background of climate change.