Fossil Fuels Feed of Energy Needs
Feeding fossil fuels to the soil: An analysis of energy embedded and technological learning in the fertilizer industry
Abstract
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 CO 2 emissions, while few learning curves exist for energy efficiency of end use technologies.
Introduction
The growth of fertilizer use is an integral part of the technological revolution in agriculture that has generated major changes in production techniques, shifts in inputs and growth in output and productivity. Although several fertilizers have been known for over a century (e.g. superphosphate production by treatment of ground bones with sulfuric acid was patented in 1842), it is only in the last 50 years that growth in fertilizer consumption has really taken place (Fig. 1). In the year 2001, about 137 million tonnes of fertilizer nutrients were applied around the world. The growth in agricultural production has been enabled by the growth of yields that has been accompanied by an increasingly intensive use of land (FAO, 2000). With higher yields normally demanding higher fertilizer application rates, and with this trend expecting to continue for the next 30 years, debate is also intensifying over the interactions between increasing fertilizer application and the effects on ecosystem stability, biodiversity and processes of climate change.
Several analyses of the energy embedded in fertilizers can be found in literature, especially in the late 1970s and early 1980s (e.g. Achorn and Salladay, 1982, Disney and Aragan, 1997, Hignett and Mudahar, 1982, Honti, 1976, Lockeretz, 1980) when higher energy prices affected the price and supply of fertilizers. Interest in the topic seemed, however, to have decreased with the fall in energy prices. Only, from the beginning of the 1990s concern for climate change (related with the high use of fossil fuels needed to produce fertilizers) increased again the attention to energy consumption and energy efficiency in fertilizer production (Worrell and Blok, 1994). This also included the indirect energy use due to increase fertilization has proven to be a determining factor on calculating the net available energy benefits of biofuels (e.g. Pimentel, 2001, Patzek, 2004, Worrell et al., 1995).
If the interactions between fertilizer application and climate change are to be better understood, there is a need for studies that analyze the role that different factors (e.g. energy efficiency, increasing fertilizer consumption) have played in the development of energy use. There is, however, a remarkable lack of this kind of studies. In this context, the purpose of this paper is two-fold. First, to analyze the impact of improvements in energy efficiency during the manufacture of fertilizers in world energy demand (due to increased fertilizer consumption), and second, to examine technological learning in the fertilizer industry. The paper is composed of two parts. In the first part, we develop historical trends of gross energy requirements by kind of fertilizer and assess the energy demand embedded in fertilizer consumption for the time period 1961–2001. Furthermore, we examine the role of fertilizer consumption, fertilizer mix and changes in energy efficiency in total energy demand. In the latter part, we explore whether technological development in the fertilizer industry can be analyzed using the concept of learning or experience curve to study energy efficiency development in the fertilizer industry.
Section snippets
Methodology
In this paper, energy and mass balances are made for the following fertilizers (see also Table 1): ammonia, ammonium nitrate (AN), calcium ammonium nitrate (CAN), urea, single superphosphate (SSP), triple superphosphate (TSP), mono-ammonium phosphate (MAP) and diammonium phosphate (DAP), muriat of potash (potassium chloride), PK 22-22 and complex fertilizers (NPK). In 2001, these fertilizers accounted for 83% of total nitrogen,1
The fertilizer sector
The fertilizer sector is defined here as the chemical or physical transformation of raw materials into mineral fertilizers. Table 1 shows typical compositions of main fertilizer products in terms of three major nutrients: nitrogen, phosphorus and potassium.2 Departing from world fertilizer
Energy embedded in fertilizer consumption
The first step to calculate the energy embedded in fertilizer consumption is to obtain historical trends in SEC for each fertilizer. The trends are then use to calculate GER using input efficiencies by process. In order to illustrate the procedure used, Fig. 3 shows how the GER trend for ammonium nitrate (AN) was obtained: from SEC trends for the production of ammonia, nitric acid and AN. Each point in the graphs represents typical SEC values for the average of plants in a given year. The
Technological improvement in the nitrogen fertilizer industry: learning curves
The results shown so far point out significant improvements in energy efficiency. In this section, we further examine the nitrogen fertilizer industry, since it accounts for over 70% of the total energy demand. As mentioned earlier, the decrease in GER values of nitrogen fertilizers has been driven by the decreasing SEC of ammonia production. It is not our intention to assess all process changes that have contributed to a reduction of the specific energy consumption in the nitrogen fertilizer
Discussion and conclusions
This paper departed from two main goals: to assess world energy demand due to fertilizer consumption and the impacts of increasing energy efficiency on total energy demand, and examining technological development using the learning curve concept. We calculate that primary energy demand for the year 2001 was about 3660 PJ, which represents about 1% of the world total energy demand in 2001. Recent data on energy consumption related to fertilizers has been published by Kongshaug (1998),6
Acknowledgements
This research has been financed by the Netherlands Organization for Scientific Research (NWO) and the Netherlands Agency for Energy and the Environment (NOVEM).
The authors are grateful to Dr. Martin Junginger and Prof. Dr. Kornelis Blok for their insights during the preparation of this manuscript and to the International Fertilizer Association for providing the production and consumption data for this study.
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Source: https://www.sciencedirect.com/science/article/abs/pii/S0921344905000819
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