Carbon Footprint Assessment of Agricultural Production Systems Under the Variable System Boundary Scenarios

Uncertainties may arise in various accounting steps involved in the carbon footprint assessment of agricultural production systems. This chapter shows the significant influence of system boundary uncertainty by presenting the results of various carbon footprint (CF) calculations according to different technical specifications. Followed by the design of enhanced models, the study revealed that the CF values of agricultural activities (ACF), farms (FCF), and agricultural products (PCF) in food production systems showed discrepant outcomes or even contrary results under different scenarios, even though they demonstrated similar carbon effect across the wheat, maize, rice, and apple crops. In scenario 4 of the system boundary, the theory of carbon-nitrogen cycle was integrated into life cycle assessment (LCA), highlighting the duality of the agricultural carbon effect. Here, the predominant carbon sources for wheat and rice production were heterotrophic soil respiration, production and utilization of raw materials, and directly N2O emission (CH4 emissions from cropland), while maize and apple production relied primarily on heterotrophic soil respiration, production and transportation of raw materials, and directly N2O emission. Carbon sequestration within soil serves as the primary mechanism for offsetting emissions in wheat, maize, and rice cultivation, while in apple production, it is the accumulation of biomass in perennial woody crops.