What is the Haber Process and are its disadvantages?
The Haber Process has been today the principal method of producing ammonia which is the most vital substance to make fertilizers, and it has contributed to agricultural intensification worldwide. In the process, ammonia is manufactured from two raw materials hydrogen and nitrogen in the following reversible reaction:
Nitrogen + Hydrogen ⬄ Ammonia
N2 + 3H2 ⬄ 2NH3
Hydrogen is made from natural gases in combustion reactions and nitrogen is made in a large scale in the fractional distillation of liquefied air. Hydrogen and nitrogen gases are mixed together in the proportions one part nitrogen to three parts hydrogen. The mixture goes into the reaction vessel and is compressed to a high pressure (200 atmospheres) and temperature (400℃) in a closed system. Then the mixture of gases from the reaction vessel is cooled down. The ammonia which has the lowest boiling point liquefied and removed separately, the unreacted hydrogen and nitrogen gases are then returned to the reaction vessel to undergo further reaction through . Afterward the ammonia produced in the Haber Process will be reacted with other different substances so as to produce artificial nitrous fertilizers. For example, the ammonium is oxidized into nitric acid and then it is reacted with ammonium gases to form ammonium nitrates, which is one of the present-day most-used nitrate fertilizers in the world (the chemical formula is shown below):
Ammonia + Oxygen ➔ Nitric acid + Water
4NH3(g) + 8O2(g) ➔ 4HNO3(aq) + 4H2O(l)
Nitric acid + Ammonia ➔ Ammonia nitrate
HNO3(aq) + NH3(g) ➔ NH4NO3(aq)
In order to produce ammonia as economically as possible, following the Le Chatelier’s Principle the best temperature and pressure are used in the Haber Process and also iron oxides are utilized as a catalyst. Therefore both productivity and efficiency of the process are truly high and it is even said it is impossible to substantially develop them even further. However although it seems to be a perfect manufacturing process, on the other side it has some disadvantages in reality.
If manufacturers are not careful, some processes can damage the environment and be a danger to people’s heaths. In order to ensure that these negative consequences do not occur the following environmental consideration are necessary: safe disposal of waste, design of plants to make it little seen and unobtrusive, reduced gas emissions, periodic shut-down for safety checks, warning and evacuation procedures for local communities and schools, reduced noise levels and slam shut valves in emergency. However since some of these factors can be really costly, there have been some cases of manufacturers avoiding to take care of them, which threatens local community and results in air pollution and destruction of ecosystems. On the other side of the coin, price of artificial fertilizers has been also cited as a problem. Although the Haber Process is efficient and effective method to produce ammonia, it is relatively expensive and so the artificial fertilizers. Most farmers in MEDC (More Economically Developed Countries) can generally afford for it, but current financial standard of people in developing countries, particularly ones in South Africa has not reached sufficient level to buy them. In 2002 thousands of people died Malawi, a country of South Central Africa due to food scarcities. A government report suggests that more than 430,000 tones of maize will be needed to avert the second food shortage in three years and this possibility is unavoidable unless they enhance the crop yields rapidly by intensifying the use of artificial fertilizers. However, currently this seems to be unachievable for both the locals and the government.
What are the negative effect of artificial fertilizers on people and the environment?
As I noted before artificial fertilizers have contributed to the world food production and in effect 40% of world’s population are alive thanks to it. However, it has many negative impacts on both the environment and people.
Certainly artificial fertilizers enable you to grow more plants efficiently at a period of time as they are made up of pure nutrients and plants can take them in directly without any biological processes in the soil. However the effect can last for one to two years in effect. Many biologists have actually suggested that this is because application of artificial fertilizers reduces the number of microorganisms in the soil because of lack of food and destroys the ecosystem. Microorganisms in soils play a vital role in not only decomposing organic matters but also supplying soils with air, spaces and heats by respiration and other activities. This naturally cultivates soils and makes them environmentally much easier for plants to send out their roots in. In essence, if microorganisms disappear from the soil where they have cultivated, due to application of artificial fertilizers, the soil becomes much harder which is difficult for plants to put down their roots, and so plants cannot take nutrients in efficiently. Therefore, as a result one or two years after applying artificial fertilizers crop yields start to decline and even it becomes difficult to grow plants in the soil anymore at the end. Although still famers can keep a high productivity by applying a huge amount of fertilizers onto the soils it is unavoidable for this to eventually contribute to reduction in crop lands, considered one of the most important elements so as to overcome the possibility of future world food shortages.
Nitrogen-nitrates, one of the most prevalently used substance of artificial fertilizers has a high solubility in water. Therefore, if farmers use excessively or apply them on the soil before a period of heavy rain, it can be washed out through the soil into a river or a lake. Then due to the accumulation of excess amount of nutrients (eutrohication) algae start to bloom dramatically which causes fluctuation in the concentration of oxygen in the ocean and result in killing fish or other aqueous living forms. Actually in Jamaica which is a truly agricultural country, over-use of artificial fertilizers has often caused eutrophication and this has resulted in smothering coral reefs and destroying the marine ecosystem of the sea around the island. Surprisingly according to research, this has nearly collapsed the entire interdependent relationship in the marine ecosystem of the island and according to WTO (World Tourism Organization), the existences of 20 percent of all aqueous organisms have been threatened.
When ammonia nitrates enter our drinking water, it can also harm people’s health. As ammonia nitrate is one of existing various forms of nitrogen-nitrates (NO3-N), it can be transformed to nitrogen-nitrite in the human digestive system through chemical reactions with digestive enzymes. The nitrites can oxidize iron molecules in hemoglobin of the red blood cells to form methemoglobin, which deprives the oxygen-carrying ability from hemoglobin. Most humans over one year of age have the ability to convert methemoglobin back to harmless oxyhemoglobin. However in the bodies of infants under six months of age as the enzyme systems for metabolizing methemoglobin are incompletely developed, methemoglobinemia (sometimes referred to as blue-baby syndrome), in which blood lacks the ability to carry sufficient oxygen to the individual body cells, causing the veins and skin appear blue can occur. According to The U.S. Public Health Service, the U.S. Geological Survey held during the period from 1970 to 1992, found that 9% of the tested private wells exceeded the recommended limit of 10mg/l nitrate-nitrogen and there were 278 occurrence of methemologlobinemia, 39 infants actually died in the same duration. And in fact this was due to the leakage of nitrogen fertilizers from agricultural lands. Since then a strict limitation has been set on the concentration of nitrogen-nitrates for public waster system in the U.S. and the number of victims of drinking-water contamination caused by artificial fertilizers have diminished. However, according to WHO(World Heath Organization) it is really difficult to search out where the nitrogen-nitrates leached out from and due to the rapidly increasing demands for food in the USA it is also problematic to strictly regulate use of artificial fertilizers. These two factors make it nearly impossible to overcome the health hazard which can stem from the use of artificial fertilizers. Actually even in the present days there have still been some cases of infants dying due to methemoglobinemia. On the other hand, a latent cancer risk from nitrogen-nitrates in water and food has been reported by some biochemists. They say there is a possibility that nitrates react with amines or amides in the human body to form nitrosamine known as a cancerous substance. In effect, there is an apparent correlation between where intensive agriculture has been flourished, which utilizes much more artificial fertilizers and where there are a number of patients suffered from cancer.
Conclusion
Through this essay, I have discovered that in contrast with the fact that most famers have relied on artificial fertilizers considering its economical positive side, it has numerous negative impacts on both the environment and people’s heaths and many negative consequences have already occurred in reality. I have also learnt that although the Haber Process which is the principal manufacturing method to produce fertilizers, has such an incredible efficiency and effectiveness this has concurrently intensified environmental destruction and kept the price of artificial fertilizers so high that many people living in LEDC cannot really afford it and suffer from food shortages due to low crops yields. Considering these points, I do not believe that intensifying production of artificial fertilizers is the best way to cope with the fast growing demands for food. It is apparent that there is a high possibility of exacerbating the problems by producing more artificial fertilizers. However taking into account the fact that 40% of world’s population are alive thanks to artificial fertilizers, at least we need to maintain the current quantity of its production. Following this, what can we do to catch up with the continuously swelling needs for food so as to avert the possibility of worldwide scarcity by 2050? Specifically there are two ideas. The first one is to make crops which can grow in deserts, cold districts and soils which contain a lot of salt. By doing this, we can convert grounds in which we could not cultivate, to agricultural lands. The another idea is to enhance the productivity of crops itself. Whatever happens the world population cannot grow by three times bigger than the current population. Therefore if we could increase the crop yields per a unit of area by three times it would be enough. In case that food is over-produced this way we can just use them as bio-fuels. In order to make these two ideas reality we will need to concentrate on advancement of genetic engineering and invest in the area. I believe that this is the realistically most reasonable way to overcome the world food shortages in the near future and the mission on 21st century’s scientists.
Bibliography
Book
-
Martin & Milner , Jean & Bryan . Reactive Science . 1st . Cambridge : Cambridge University Press, 2004.
-
McDuell , Bob . Examining GCSE Chemistry . 1st . London: Century Hutchinson Ltd , 1989.
Websites
-
Nitrate - Nitrite Nitrogen ." Water Watch . 6 Apr 2008 <http://www.state.ky.us/nrepc/water/wcpno.htm>.
-
"Nitrogen-nitrates & nitrites ." Goo . OKWave . 6 Apr 2008 <http://oshiete1.goo.ne.jp/qa3372202.html>.
-
"Haber Process ." Wikipedia - Fre Encyclopedia . 6 Apr 2008. Wikipedia . 6 Apr 2008 <http://en.wikipedia.org/wiki/Haber_process>.
-
Production of artificial fertilizer." Production of artificial fertilizer. 6 Apr 2008 <http://www.lcafood.dk/processes/industry/fertilizer.htm>.
-
"硝酸性・亜硝酸性窒素による地下水の汚染について." Hokkaido Environment Organization. Hokkaido Environment Organization. 6 Apr 2008 <http://www.pref.hokkaido.lg.jp/ks/khz/contents/mizukankyo/suisituhozen/syou/syou.htm>.
Images
-
Googler. World Population. 05 Mar 2008 < http://gigazine.net/>
-
Healthvee. Healthy food. 05 Apr 2008 <http://healthvee.com/ja/acne/natural-way-to-stop-acne/>
Appendices
This section explains why nitrogen, phosphorous and potassium are essential macronutrients for plants and needed in a large quantiry.
There are several reasons for this: 1. Nitrogen is required to build up plants protein in the plant as every amino acids which are chained up to form protein molecules contain nitrogen, 2. Phosphorous is contained in all molecules which make up our cells’ membranes (phospholipids) and ATP that are main energy source of all cells. Also phosphorous is required to produce a good root system, 3. Potassium is essential chemical to any plants for metabolism and plants need it for forming flowers and seeds. Also it generally makes up of around two percent of the weight of plants. In essence, without these three macronutrients - Nitrogen, phosphorus and potassium, the plant simply cannot grow as it cannot make the pieces it needs and It is like a car factory running out of or a road crew running out of asphalt.