The Nitrogen Fertilizer Industry

The Nitrogen Fertilizer Industry

It was not until the early years of the 20th century that processes were developed for capturing atmospheric
nitrogen - firstly by passing air through an electric arc to produce nitric acid and calcium nitrate, then by
reacting lime and coke in an electric furnace to produce calcium cyanamide, and then, most notably, by
synthesizing nitrogen and hydrogen catalytically, using a process developed by the German scientists,
F. Haber and C. Bosch. These processes 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.
Ammonia synthesis requires large amounts of energy. Initially, this was provided by cheap electricity
and derivatives of coal (water gas process or cryogenic separation of hydrogen from coke oven gas).
These feedstocks were available only in industrialized countries. Subsequently, more economic processes
were developed which involved the partial oxydation of hydrocarbons by pure oxygen and steam and the
tubular reforming of natural gas or naphta by steam. Again, these developments were initially restricted
mainly to the industrialized countries, because of large investment costs and difficult logistics. However,
from the 1960s onwards, the larger developing countries, especially in Asia, began increasingly to
subsidize the production and consumption of fertilizers, assisted by the major international agencies.
The naphtha and fuel oil based processes were rendered relatively uncompetitive by the first oil crisis in
1974. Fortunately, more and more natural gas became available as well in Europe as in developing countries.
Most new plants from the mid-60s onwards were built to use natural gas, thus enabling the former Soviet
Union, certain countries in Eastern Europe and numerous developing countries with extensive gas
sources to develop large ammonia-based fertilizer industries.
The early nitrogen fertilizers - sodium and calcium nitrates, calcium cyanamide and ammonium sulphate
- contained only 15-21% N. Of course, this was vastly more than the typical 1-1.5% total nutrient content
in animal manures, but less than could be achieved using ammonia to produce ammonium nitrates. By the
1960s, ammonium nitrate (34% N, 35% when pure) and calcium ammonium nitrate (27% N) had become the
leading nitrogen fertilizers. However, the development of ever larger, gas-based ammonia plants, affording
large amounts of by-product carbon dioxide allowed for utilizing this carbon dioxide in the manufacture
of urea. Urea is the product of the reaction of ammonia with carbon dioxide. It contains 46% N.
Consequently, it offered a further significant advance in plant nutrient concentration, and hence in
savings in nutrient transportation and distribution. Today, it is one of the most common nitrogen fertilizer.
Let us mention moreover the use -mainly in the USA, of liquid NH3
as a fertilizer.
Nevertheless, the less concentrated nitrogen fertilizers continue to occupy an important place in numerous
countries. Among these products, ammonium sulphate is in a somewhat special position, being a byproduct
of the manufacture of caprolactam and coke-oven gas.
Ammonium bicarbonate became particularly important in China in the 1950s, as a fertilizer which could be
relatively easily produced in small-scale coal-based plants. Ammonium chloride was another lowconcentration
product which had local importance in some countries, notably Japan.