Feeding fossil fuels to the soil: An analysis of energy embedded and technological learning in the fertilizer industry

In this paper, we assess energy demand due to fertilizer consumption in the period 1961–2001. Based on historical trends of gross energy requirements, we calculated that in 2001, global energy embedded in fertilizer consumption amounted to 3660 PJ, which represents about 1% of the global energy demand. Total energy demand has increased at an average rate of 3.8% p.a. Drivers behind the trend are rising fertilizer consumption and a shift towards more energy intensive fertilizers. Our results show that despite significant energy efficiency improvements in fertilizer manufacture (with exception of phosphate fertilizer in the last 20 years) improvements in energy efficiency have not been sufficient to offset growing energy demand due to rising fertilizer consumption. Furthermore, we found that specific energy consumption of ammonia and urea developed in close concordance with the learning curve model, showing progress ratios of 71% for ammonia production and 88% for urea. This suggests an alternative approach for including technological change in energy intensive industries in middle and long-term models dealing with energy consumption and CO2 emissions, while few learning curves exist for energy efficiency of end use technologies.