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The Incredible Journey of Nitrates and Ammonia D.K. Srivastava & V.S. Ramamurthy

The recent devastating explosion in Beirut was caused by 2750 tons of ammonium nitrate, a chemical compound commonly used as an agricultural fertiliser, but also known as the grandfather of explosives.

T was on the evening of 4 August 2020, that Beirut, the capital city of Lebanon, Iwitnessed one of the largest industrial accidents amid the COVID-19 pandemic and an economic crisis. A powerful explosion sent a huge orange fireball into the sky, followed by a massive shock wave that overturned cars, damaged buildings, and shook the ground across the city killing at least 220 people, injuring more than 5000 and leaving an estimated 300,000 people homeless. The explosion was caused by 2750 tons of ammonium nitrate, a chemical compound commonly used as an agricultural fertiliser, which had been stored at the port warehouse for six years. Serious industrial disasters caused by ammonium nitrate were not Aftermath of the Beirut explosion (commons.wikimedia.org) uncommon in the past. Explosions due to Roger Pauly, writing in “: The Life History tons of ammonium nitrate on ships and in storage facilities of a Technology” suggests that, “While was have caused hundreds of fatalities apart from damage to primarily a Chinese innovation, it may have received some structures, vehicles and even planes flying overhead. Indian inspiration. Just as China embraced Indian Buddhism, It is therefore not surprising that the news of about 740 the subcontinent’s fascination with fire may have crossed the tons of ammonium nitrate being stored in a container about Himalayas. In 664 AD an Indian visitor to China reportedly 20 kilometres away from the city of Chennai evoked such a demonstrated the peculiar flammability of saltpetre and panic amongst the public that the authorities had to complete provided instructions on how to locate it.” Arnold Pacey the process of disposal in a very short time and start moving (Technology in World Civilization: A Thousand-year History) the chemical away from there. adds, “Later Chinese studies of the chemistry of saltpetre Because of its easy availability, ammonium nitrate has show other evidence of Indian influence which seems to have also been used often by terrorists. been the starting point for the Chinese investigations which led to the first recipes for gunpowder.” Ammonium Nitrate – Grandfather of Explosives For centuries India was the biggest producer and exporter of potassium nitrate or saltpetre or “shora”. With charcoal and Sulphur, it produces an explosive mixture, which we now call gunpowder. Explosives were repeatedly mentioned by Kautilya in his Arthashastra, as “agniyogas” and “agnisamyogas” (https://csboa.com/eBooks/Arthashastra_ of_Chanakya_-_English.pdf). Some historians also suggest that Vaishampayan’s Nitiprakashika compiled in 800 BC and Shukraniti attributed to Shukracharya compiled perhaps earlier have mentions of explosives made using saltpetre, coal, and Sulphur. Saltpetre

36 | Science Reporter | November 2020 It is generally believed that the Chinese started using started using it for the subjugation of natives, extraction of gunpowder to make fireworks for display by 700 AD and gold, capture of territories and slaves, and piracy on the high the Mongols may have learned its use from them. The first seas; all of which led to their ascent. Saltpetre was one of the confirmed reference to what can be considered gunpowder most important chemicals exploited by the Europeans in their in China occurred in the 9th century AD, first in a formula initial trading days in India. contained in the “Taishang Shengzu Jindan Mijue” in 808, The Dutch is believed to have taken and then about 50 years later in a Taoist text known as between 3,000,000 to 3,500,000 Dutch lbs. per year for the “Zhenyuan miaodao yaolüe”. Holland alone, during the first two decades of the eighteenth Rana Hammirdeva of Ranthambore used gunpowder century (Susil Chaudhuri, Proceedings of the Indian History against the army of Alauddin Khiliji in early 1300 AD; there Congress, 1973, Vol. 34, 1973). In the year before the battle of are indications that some Mongol deserters from the latter’s Waterloo (1815) the East India Company exported 7300 tons army may have brought this technology with them. There of saltpetre to England (Robert Montgomery Martin, Statistics are reports of extensive fireworks in Vijayanagaram in 1443 of the Colonies of British Empire). The British victory at during the reign of Devaraya II during Mahanavami festival Waterloo was facilitated by the use of Indian saltpetre which in 1443, which may have used gunpowder. There is strong was far superior to the charcoal-like French product. During evidence to suggest that Chutia kings of Assam, used hand the American Civil War (1861-1865), Great Britain provided (hiloi) as well as canons (bortop) against the invading saltpetre from India to the two warring factions. Ahoms in 1524 AD. Later, Ahoms used it against Turbak Around this time, and his son Khan, the commander of Gaur in 1532 AD. started making very accurate and powerful . Their main contribution was to fill the gunpowder in iron pipes and tie these pipes to long bamboo sticks, to guide them. During the Second Anglo-Mysore War (1861), Hyder Ali’s rockets had destroyed Colonel William Baillie’s ammunition stores, which contributed to a humiliating British defeat. Tipu Sultan greatly improved his rockets and deployed it extensively and very effectively.

One of the guns which the Ahoms procured after defeating the Chutias in 1524 AD (Wikipedia) The First Battle of Panipat, on 21 April 1526, was fought between the invading forces of Babur and the Lodi dynasty. The battle is known for the use of gunpowder firearms and field . It is generally believed that Babur got this knowledge from Turks, who may have learnt the use of gunpowder from Mongols, who in turn had learnt it from Chinese. It has been reported by Nathan (Baharistan-I- Ghaybi, M.I. Borah (tr.), Vol. I) that when Raja Pratapaditya of Jessore Painting of Mysore Man by Robert Home (Wikipedia) surrendered to Islam Khan in 1609, he agreed to provide 41 tons of gunpowder in addition to twenty thousand infantry and five hundred war-boats. About 50 years later, when Mir Jumla invaded Assam in 1662-1663 AD, he left with 675 big guns and 190 tons of gunpowder in boxes because they were of much better quality than what he was using. One of the reasons for the defeat of Nawab Sirajuddaula at Battle of Plassey in 1757 was that his gunpowder became wet due to heavy rain during the battle, while Robert Clive used tarpaulin to cover his gunpowder and “kept it dry”. This victory gave the English East India Company a monopoly over the vast sources of saltpetre in Bihar. It is truly said that “gunpowder and the blew up the medieval world A painting by Charles H. Hubbell showing the Mysorean army economically and politically”. fighting the British forces with (Wikipedia, NASA)

Saltpetre from India on the World Stage Why Bihar produced good quality saltpetre in such Earlier, European powers, which had made considerable vast quantities? Ashutosh K. Jha (Production of Saltpetre technological development in the use of gunpowder, had in Medieval India) writes that in this region, “… agriculture

November 2020 | Science Reporter | 37 is the chief occupation and there is consequently a high The world produced more than 170 million tons of proportion of domestic animals. Thus, the soil around the ammonia in 2019. Ammonia is used for the production of villages has an abundant supply of organic nitrogen. The fertilizers like ammonium sulfate, ammonium phosphate, climatic conditions of temperature and humidity are also ammonium nitrate and urea. It is also used for the synthesis unusually favourable for the growth of so-called nitrifying of nitric acid, which in turn is used in making explosives such bacteria, which convert ammonia by successive stages into as TNT, nitroglycerine used as a vasodilator (a substance that nitrous and nitric acid. Wood and cow dung are largely used dilates blood vessels) and PETN (pentaerythritol nitrate), for fuel, and the immediate vicinity of each village thus forms sodium bicarbonate, sodium carbonate, hydrogen cyanide, a perfect laboratory for the formation of Potassium Nitrate. and hydrazine (used in rocket propulsion systems). In the long period of continuous surface desiccation which It is also used for making fibres like nylons and plastics, follows a small monsoon rainfall, the compound so formed used in large scale refrigeration plants and air-conditioning in the soil is brought to the surface by capillary action and units, and for making ice. Ammonia is an important input for appears as an efflorescence of salt which is collected and the pharmaceutical industry, pulp and paper industry, mining, purified.” and metallurgy, etc. Ammonium nitrate is also used as an By mid-nineteenth century nitrate from Atacama Desert oxidizer in rocket propellants and a nutrient for yeast and of Peru was available and India’s monopoly of saltpetre was antibiotics. challenged. The nitrates also used to be obtained from the walls of caves where the salts were brought to the surface Green Revolution and its Aftermath by moisture or from droppings of some seabirds or bats. Nitrogen has always been the most abundant gas in the The development of smokeless explosives like cordite and atmosphere since life was established on the planet Earth. later TNT reduced the use of saltpetre for making the black However, nitrogen atoms form a diatomic bond with each gunpowder. other, and the atoms cannot be taken up by organisms. The rate of conversion of atmospheric nitrogen to organic nitrogen Haber-Bosch Process is controlled by the enzyme nitrogenase. This enzyme is By the time of the First World War, Fritz Haber along with present in very few bacteria that live mostly associated with Carl Bosch had developed a process for industrial production the roots of certain plants of legumes. For centuries, farmers of ammonia, using what is now called Haber-Bosch process, across the world have been rotating crops like wheat with which can easily be converted to nitrates for making fertilizers such crops of legumes, to take advantage of this process. as well as explosives and thus, the obstruction of the ships Thus, in the biological nitrogen fixation, the largely bringing nitrates to Germany from Peru had only a limited un-reactive molecular nitrogen is reduced to ammonium effect on them. compounds. The fixed nitrogen is subsequently transformed The Haber-Bosch process revolutionized the availability into a wide range of amino acids and oxidized compounds of fertilizers and increased the production of food grains by micro-organisms and finally returned to the atmosphere as considerably. It is known that the supply of reactive nitrogen is molecular nitrogen through microbial denitrification in soils, essential for all life forms. Thus, increases in nitrogen supply fresh and marine waters, and sediments. have been exploited in agriculture to increase the yield of crops Ammonium nitrate, when applied to crops as a fertilizer, and provide food for the growing global human population. It provides half of its nitrogen in the nitrate form and other half has been estimated that almost half of the human population at in the ammonium form. The nitrate form moves readily with the beginning of the twenty-first century depends on fertilizer soil water to the roots, where it is immediately available for nitrogen for their food (J. Erisman, M. Sutton, J. Galloway, plant uptake. The ammonium fraction is taken up by roots or et al., How a century of ammonia synthesis changed the gradually converted to nitrate by soil microorganisms. world, Nature Geosci. 1, 636–639, 2008). Fritz Haber won However, the excessive use of fertilizers is not without the Nobel Prize in Chemistry for this in 1918, though this problems. The main problem is that a lot of that fertilizer is decision created some controversies as it came soon after the wasted — more is applied than plants can absorb — and it First World War. washes out of the soil into waterbodies, or evaporates into the The story of Fritz Haber will not be complete unless we atmosphere in the form of nitrous oxide, a potent greenhouse recall his role in the production of poisonous gases for use in gas as well as a major ozone-depleting agent. Other risks warfare during the First World War. The chemists of France include threats to human health through nitrate pollution in and Great Britain also lent their support to the production of drinking water, to fish and other wildlife through fertilizer poisonous gases. It is estimated that up to one million soldiers run-off causing low oxygen “dead zones” due to algal blooms. succumbed to these attacks. When the wife of Fritz Haber, Repeated use of ammonium nitrate can increase the Clara Immerwahr Haber, the first PhD in chemistry from acidity of the soil, even though it causes less increase in Germany, came to know of the first batch of 6000 soldiers acidity as compared to ammonium sulphate, another popular killed by the gases made by her husband in an attack supervised fertilizer. Urea is another fertilizer derived from ammonia. by him, she committed suicide. Haber is also credited with On being used, urea first reacts with water and is converted to the comment, “During peace, scientist belongs to the world, ammonium bicarbonate. If the soil has high pH, ammonium during the war he belongs to his country”, to justify his role bicarbonate can be further converted to ammonia gas, which in the production of poison gases. leads to a significant loss of nitrogen. However, compared

38 | Science Reporter | November 2020 to ammonium nitrate and ammonium sulfate, urea produces SOLAR ENERGY POTENTIAL IN GWP OF TOP 10 STATES less acidity and typically does not affect soil pH significantly. 142.31 The use of fertilizers also requires sufficient irrigation. Installed Potential

Farmers across India and elsewhere have met this increasing 111.04 demand of water by using deep bore-wells, which has greatly lowered the water tables. These require to be recharged, 64.34 urgently, by rainwater harvesting and construction of check 61.66 dams. Drip irrigation could help in preserving water but 38.44 35.77 33.84 25.78 requires a large investment. 24.7 22.83 Let us also recall that most of the hydrogen (95%) 7.27 4.84 3.6 2.95 2.3 1.8 1.09 0.4 0.02 necessary for the production of ammonia is produced from 0.03 fossil fuels by steam reforming of natural gas, partial oxidation ODISHA LADAKH of methane, and gasification of coal. Each of these emits GUJARAT RAJASTHAN KARNATAKA copious amounts of carbon dioxide which further exacerbates MAHARASTRA UTTAR PRADESH MADHYA PRADESHANDHRA PRADESH the climate change. We get 5 kg to 16 kg of carbon dioxide for HIMACHAL PRADESH every kg of hydrogen, depending on whether we use methane Fig. 1: Solar energy potential of top ten states of India or coal. land etc., estimated by National Institute of Solar Energy, Ministry of New and Renewable Energy of the Government Green Hydrogen and Green Ammonia of India. This energy can be harvested to provide us either Immediate deployment of renewable and green energy Green Hydrogen or Green Ammonia to meet our needs of is considered as the only solution to meet the challenge of clean energy as well as ammonia for production of Green keeping the rise in global temperature to less than 2 degree Fertilizers. Celsius compared to pre-industrial revolution values and to To illustrate this potential, we just look at two regions, reduce the net emission of carbon dioxide to zero by 2050. Rajasthan and Ladakh. Their combined solar energy potential However, we also know that renewable energy sources have is 250 GWs. Considering eight hours of sunshine, this would strong variability due to the day/night and seasonal variations. mean about 2000 GWh of electricity every day. The electricity There are also likely to be phases when the production of needed to produce one kilogram of nitrogen from hydrolysis of power is much more than what we may need. water, after taking the efficiency of electrolyzers into account There have been suggestions of batteries (too expensive is about 50 kWh. This would then translate to a production of and not enough capacity yet) and pumped-up hydroelectric 40,000 tons of hydrogen per day. plants (not enough suitable sites with uniform distribution). If the process of ammonia formation in the electrolyzer An entirely different approach which has been suggested cells can be realized, it will translate to 225,000 tons of involves using electrolysis of water to produce hydrogen and ammonia per day. This would amount to more than 80 million oxygen. This hydrogen can be used in internal combustion tons per year of ammonia. This can be compared to the current engines or fuel cells to run motor vehicles, trains, buses, cars, production of 20 million tons of ammonia per year in the planes, and ships. The hydrogen can also be transported using country in a very energy and carbon-intensive Haber-Bosch pipes or compressed or liquified and taken to wherever it is process. Thus, two vast deserts of the country can provide needed. This, of course, is a green source of energy and a vast resource of Green Electricity, or Green Hydrogen, the hydrogen thus produced is called “Green Hydrogen”, for or Green Ammonia and contribute to the prosperity of the obvious reasons. country. It has also been suggested that the hydrogen can be Nitrates and ammonia have played a very fascinating role converted to ammonia, which is easier to transport, as it is for humankind during wars and peace. We suggest using the very easy to liquify. If one needs hydrogen at the destination, abundant sunshine to produce not only Green Electricity, but it can be recovered by cracking. This ammonia will also also abundant supply of Green Hydrogen, Green Ammonia, remain “Green” as no carbon dioxide emission is expected and Green Fertilizers, without harming our climate or leading at any stage. to global warming. While studying the electrolysis of water in 1809, Humphrey Davy had reported observation of a small amount Prof. D.K. Srivastava ([email protected]) is of ammonia along with the hydrogen gas at the cathode. This presently Homi Bhabha Chair Professor at National Institute of was due to presence of the nitrogen dissolved in the water Advanced Studies, Bengaluru. A Fellow of the National Academy which interacted with the nascent hydrogen to make ammonia. of Sciences, India and Indian National Science Academy, he retired There are efforts to make this more efficient by increasing the as Director and Distinguished Scientist at the Variable Energy amount of nitrogen near the cathode to produce ammonia on Cyclotron Center, Kolkata. a commercial scale. This would be “Green Ammonia” and Prof. V.S. Ramamurthy ([email protected]) is a well- can be used for production of fertilizers which will also be known Indian nuclear scientist. He has been Director, Institute of “Green”. Physics, Bhubaneswar and also Secretary, Department of Science & Figure 1 shows the solar energy potential of top ten states Technology (DST), Government of India. Prof. Ramamurthy was of India, which includes the considerations of availability of awarded the Padma Bhushan by the Government of India in 2005.

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