Carbon Footprint Assessment for the Production Cycle of Value-Added Diammonium Phosphate Containing Humic Acid

In this paper, the carbon footprint of value-added diammonium phosphate containing humic acid (DAPH) were analyzed, calculated, and evaluated in order to provide a scientific basis and theoretical support for the study on the carbon footprint of value-added fertilizers.

The industrial production process of product (from "cradle" to "gate") was defined as the production cycle of product in this study, and the carbon footprint of diammonium phosphate (DAP) and DAPH products was calculated and evaluated referring to the life cycle assessment and PAS 2050 standard.

(1) In terms of phosphorus nutrients (P₂O₅), the carbon footprint of DAP and DAPH production cycle was 3 636.73 kg CO₂-eq·t^-1 P₂O₅ and 3 653.16 kg CO₂-eq·t^-1 P₂O₅, respectively. The carbon footprint (in terms of P₂O₅) of DAPH was only increased by 0.45% compared with DAP. In terms of physical quantity (1 t fertilizer product), the carbon footprint of DAP and DAPH production cycle was 1 672.90 kg CO₂-eq·t^-1 and 1 660.38 kg CO₂-eq·t^-1, respectively, and the carbon footprint of DAPH (in terms of physical quantity) decreased by 0.75% compared with that of DAP. The difference of carbon footprint between DAP and DAPH was attributed to the addition amounts of humic acid synergist (HAS). (2) The carbon footprint of synthetic ammonia accounted for 67.87% and 67.57% of the carbon footprint of DAP and DAPH production cycle, respectively, which was the largest contributor for the carbon footprint of DAP and DAPH during the production cycle. However, the carbon footprint increased by adding HAS only accounted for 0.45% of the carbon footprint of DAPH.

Adding HAS had little effect on the carbon emissions during the DAP production, while synthetic ammonia was the biggest factor affecting the carbon footprint of DAP production cycle.