MINERAL NITROGEN FERTILIZERS: ENVIRONMENTAL IMPACT OF PRODUCTION AND USE - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 9

T HE N ITROGEN F ERTILIZER I NDUSTRY
Fertilizer production currently account for about 2-3% of the total global energy
consumption. Nitrogen fertilizers are responsible for the majority of this consumption
(European Commission, 2006). Most of the energy is required by the fixation of atmospheric
nitrogen to manufacture ammonia. Considerable energy is also required for the conversion of
ammonia to urea.
The energy required for nitrogen production is fairly evenly distributed around the planet
and there is production in every region. However, there is a trend towards increased
production in locations where cheap natural gas is available, in areas such as the Middle East
and the Caribbean and also in the main regions of consumption, such as South Asia and
China.
P RODUCTION P ROCESSES
Ammonia
Ammonia (NH 3 ) is the primary input for the majority of worldwide nitrogen fertilizer
production (97% of N-fertilizer is derived from ammonia) (European Commission, 2006).
Ammonia production is largely based on modifications of the process developed by the
two German scientists Haber and Bosch in the early years of the 20 th century. NH 3 is
synthesized from a 3:1 volume mixture of hydrogen and nitrogen at elevated temperatures
and pressure in the presence of an iron catalyst (Wood & Cowie, 2004). This process
revolutionized the nitrogen fertilizer industry, breaking the former dependence on the
relatively rare mineral sources of nitrogen and enabling the development of products with a
higher nitrogen content. The first Haber-Bosch plant was opened in 1913, and nitrogen
production has been largely dependent on ammonia synthesis ever since (UNEP/UNIDO,
1998) .
All the nitrogen used is obtained from the air and the hydrogen may be obtained by either
of the following processes:
a) steam reforming of natural gas or other light hydrocarbons (Natural Gas Liquids,
Liquefied Petroleum Gas or Naphtha);
b) partial oxidation of heavy fuel oil or coal;
c) coal gasification.
Around 77% of world ammonia production is based on natural gas steam reforming
(Figure 3), 14% on coal gasification, mainly in China, and 9% on the partial oxidation of oil
products and heavy hydrocarbon fractions, mainly in India and to a lesser degree in China.
The synthesis of ammonia is a very energy demanding process based on an industry wide
benchmarking study conducted by IFA the average energy requirements for ammonia
production is 36.9 GJ/t, and ranges from 28 to 53 GJ/t of ammonia (Chinese plants were not
considered) (Table 5).