The environment is stabilized by the biogeochemical cycles. Biogeochemical cycles are the processes that occur naturally and recycle the nutrients in different chemical forms from the non-living ecosystem to living organisms and then back to the non-living ecosystem. Biogeochemical cycles consist of five cycles which are iron cycle, sulphur cycle, phosphorus cycle, nitrogen cycle and carbon cycle. The most important and complex of biogeochemical cycles is the nitrogen cycle (Botkin & Keller, 2012). Nitrogen cycle allows the various nitrogenous species to cycle among the inert nitrogen gas in the atmosphere and soil (Newton, 1999). According to Newton (1999), “the nitrogen gas molecule is fixed by either natural processes, which include both biological and non-biological (lightning, combustion and volcanism) systems, or man-made processes (mainly industrial ammonia production)” (p. 1). There are four processes in the nitrogen cycle, namely nitrogen fixation, decomposition, nitrification, and lastly, denitrification (refer to Figure 1 in Appendix 1).
Firstly, the cycle involves nitrogen fixation. Nitrogen fixation is a process of forming ammonia (NH3) or nitrate (NO3-) from inorganic nitrogen in the atmosphere. Organisms are not able to consume the molecular nitrogen directly. As a result, plants and organisms must consume the nitrogen in stable compound for example nitrate ions (NO3-), ammonia (NH3) and urea (NH2)2CO. Bacteria are the only organisms that capable to produce ammonia from nitrogen gas. Moran et al. (2012) reported that cyanobacteria performed half of the nitrogen fixation while the other half is from soil bacteria. Nitrogen fixation helps in preventing overall nitrogen deficiency (Newton, 1999). Nitrogen fixation occurs in three categories which are atmospheric, industrial and biological fixation.
Atmospheric fixation involves energy from the lightning and the formation of acid rain. During lightning, the nitrogen oxides can be formed when the nitrogen molecules are broken and combine with the free oxygen in the atmosphere (Botkin & Keller, 2012). The nitrate formed from dissolved nitrogen oxides in the water, which is then carried to land. For acid rain formation, nitrate oxide is added into the atmosphere as nitrogen gas and oxygen gas combine from burning fuel at high temperature. In the atmosphere, Miller (2007) described the production of nitrogen dioxide gas and nitric acid as a result of combination between nitrogen gas and oxygen gas, which return to the earth’s surface as acid rain.
For industrial fixation, the formation of ammonia is occurred through the combination of atmospheric nitrogen and hydrogen. The production of ammonia is made by the Haber process under high pressure, at 600 degrees celsius and aid of a catalyst (Lim & Yip, 2011). Ammonia is used widely in manufacturing of fertilizer such as urea, ammonium sulphate and ammonium nitrate. According to Botkin & Keller (2012), scientist discovered that electric...