Greenhouse gas emissions and
fertilizer production

Improvements to the Haber-Bosch process for ammonia production have been made, but the process has remained virtually unchanged for more than four decades. (Graphic 1)

The nitrogen fertilizer industry is an energy-intensive industry, producing CO₂ from both process (feedstock) and fuel sources. According to the latest IFA benchmarking exercise, the CO₂ generation from ammonia production ranges from 1.52 to 3.06 tonnes of CO₂ per tonne of ammonia produced for the 66 participating ammonia plants². On average, one-third of CO₂ emissions is from burning fuel and two-thirds are from the use of hydrocarbon feedstock. Natural gas is the dominant feedstock (graphic 2).

The survey also revealed that some 38% of the CO₂ produced was recovered. Many facilities utilize all or part of the process-generated CO₂ for urea production. About 28% of the CO₂ produced globally is captured for urea production³. Carbon dioxide generated by the fertilizer industry is also sold, for example, to the oil and gas industry (for injection into wells) or to the beverage industry.

Nitric acid (HNO₃) is produced by fertilizer companies for the manufacture of ammonium nitrate (AN) and related products. As HNO₃ is produced from ammonia (NH₃), nitrous oxide (N₂O) is emitted proportional to the amount of NH₃ used or the amount of HNO₃ produced. The concentration of N₂O is also influenced by engineering factors such as burner design, burner temperature, pressure, catalyst age, etc.

Graphic 1

Graphic 2

 

The fertilizer industry is continually improving its efficiency and reducing emissions

The industry has already come a long way towards reducing energy use and related emissions. Recent ammonia factories use some 30 per cent less energy per tonne of nitrogen produced than those designed around 1970. Over the same period, greenhouse gases from fertilizer production have been reduced by at least 20 per cent. The best-performing sites today approach the thermodynamic optimum (i.e. the minimum energy consumption required by the chemical reaction) for ammonia synthesis.

In 1998, the global fertilizer industry’s greenhouse gas emissions were calculated to be to the order of 283 million tonnes CO₂ equivalent (CO₂-eq.) per year (134 million tonnes CO₂-eq. as flue gas from energy production, 74 million tonnes CO₂-eq. as nitrous oxide from nitric acid production and 75 million tonnes as pure CO₂)⁴. Since then, ammonia production has grown by about 16%. However, emissions have not increased in a linear fashion for a number of reasons:

• Many inefficient production sites have been closed, thus raising the average efficiency.

• Some older facilities have been revamped. The revision of an existing plant can increase its energy efficiency by some 15%, at a cost of between USD 8 and 20 million per site.

• Management innovations have improved the efficiency of many facilities.

• Nitric acid production is often a component of integrated fertilizer manufacturing plants. New technologies are under development to control N₂O emissions from this process. A number of factories have benefitted from carbon trading mechanisms in order to abate their N₂O emissions, and others are expected to follow.

IFA carries out a biennial benchmarking survey that allows member companies to compare their energy performance to the industry standard and to identify areas for improvement.