CO2 Emissions from Urea Fertilizer in Pakistan, China, India, and the USA: A Comparative Analysis Using the IPCC Model

The application of urea in agricultural practices leads to carbon dioxide (CO2) emissions through hydrolysis. Urea, when applied to soil, reacts with water and undergoes hydrolysis, releasing ammonia (NH3) and CO2. This reaction is facilitated by soil enzymes such as urease. The released NH3 can further undergo nitrification, producing nitrate (NO3−) and nitrous oxide (N2O). While CO2 from urea hydrolysis is relatively small compared to other sources, cumulative emissions from agricultural activities contribute significantly to climate change and agriculture’s carbon footprint. A straightforward calculation model (CO2 = A × 0.73) was employed to approximate CO2 emissions in various countries based on annual urea usage. In this model, China led emissions with 40,483 Gg yr−1, followed by India (26,031 Gg yr−1) and the USA (12,032 Gg yr−1). Out of total annual emissions (94,763 Gg), China contributed 43%, India 27%, the USA 13%, the EU 8%, Pakistan 5%, and Indonesia 4%. China’s CO2 emissions from urea were 16% higher than India, 30% higher than the USA, 35% higher than the EU, 38% higher than Pakistan, and 39% higher than Indonesia. As expected from the deterministic IPCC formula (CO2 = Urea × 0.73), the relationship between urea consumption and CO2 emissions is linear with a slope of 0.73. Linear regression shows that for every 1000-ton increase in urea consumption, CO2 emissions increase by 730 tons (0.73 Gg) (R2 = 0.99, p < 0.001). Pakistan’s urea consumption grew at an average annual rate of 2.2% from 2015 to 2023, with corresponding CO2 emissions increasing from 4015 to 4788 Gg yr−1 (total increase of 20% over eight years). Optimizing fertilizer application rates, timing, and methods to enhance nutrient uptake efficiency, along with sustainable agricultural practices (organic matter management, conservation tillage, and precision agriculture), can help mitigate environmental impacts. This study emphasizes implementing sustainable agricultural practices and integrated nutrient management to minimize CO2 emissions from urea application, enabling agricultural systems to contribute to climate change mitigation and reduced carbon footprints.