Unless, unlike me, you are a bit of a boffin, ammonia and how it benefits us does not figure much in our awareness. In fact, to many, it is a much-maligned mixture of elements. After all, it smells terrible to most people and if it is concentrated to high levels, such as in untreated wastewater, it can be highly toxic to the environment.
However, the reality is that ammonia is not only essential for all organic life but, since the development of methods of manufacture at an industrial scale, it has also helped immeasurably in improving global health, and has been the lynchpin for an unprecedented economic surge.
Ammonia (chemical formula NH3) is a common natural mixture, or compound found in humans and in the environment, and occurs both terrestrially and in undreamed of, and as yet unattainable, quantities in the outer planets of our own solar system. It is one of the most commonly produced chemicals in the world and is used in large amounts in agriculture, industry and commerce. In nature, ammonia forms an integral part of the nitrogen cycle and is produced in soil from bacterial processes during the decomposition of organic matter. It is the driver for new life, with an effectiveness that is evidenced by every tree, flower or animal.
Ammonia is used in many and varied products, ranging from fertilisers to everything from refrigeration to pharmaceuticals to explosives to cleaning products. In this latter product, ammonia gas is mixed with water to a concentration of between 5 and 10% and is a critical agent in protection from bacterial infection. It has to be stressed, however, that its direct ingestion as a cure for, or protection against infectious microbes, although tentatively promoted by some influential sources, is expressly recommended against.
Ammonia then, is obviously a very useful product. However, as already noted, if not carefully handled, it can be highly toxic to the environment. There have been several recent incidents where unconstrained chemical release into rivers has resulted in significant damage to life that depends on water for survival. This includes several infamous mass fish-kills caused by the uncontrolled accumulation of fertilisers seeping into rivers and the sea from fields or from upriver factory spills.
Industrially made, or brown, ammonia is produced in an intimidating-sounding procedure known as the Haber-Bosch process. The process was developed by two gentlemen called Fritz Haber and Carl Bosch in early 1900s and involves reacting nitrogen taken from the air together with hydrogen from methane under conditions of 200 atmospheres, at temperatures of 450°C and in the presence of an iron-based catalyst. Its development signified a huge technological advancement and led to both an arms race and a population explosion, as large quantities of ammonia for the manufacture of explosives as well as the growth of food became more easily available.
The usefulness of ammonia has resulted in new interest in finding other ways to produce it that does not rely on fossil fuel. Apart from ‘brown’ ammonia, produced solely from fossil fuel, other mechanisms of manufacture are being developed. ‘Blue’ ammonia is similar to brown ammonia, but the released carbon is removed, or sequestered, before it can escape to the atmosphere. Green ammonia is made from air and water using only renewable energy, while a new variety, ‘emerald’ ammonia is reclaimed ammonia from wastewater using renewable energy.
One property already noted, that could make ammonia a potent weapon in the battle against global warming, is that it is combustible. This makes it a viable alternative to the use of fossil fuel in spark ignition engines for power production, and there are currently several studies under way to assess the viability of replacing fossil fuels with zero carbon producing ammonia in marine engines. Shipping is an industry that, whilst accounting for much less CO2 emissions than aviation, is an important contributor to the burgeoning greenhouse effect, so a fuel that does not produce carbon dioxide will no doubt be a significant boon to the transport of a whole range of goods around the world.
The properties of ammonia, coupled with the fact that it can be produced using renewable energy, clearly illustrate its potential importance against global warming. In recent years, as more people have become aware of the environmental consequences of their actions, significant advances in greenhouse gas reductions have been made. One of the pillars of this has been the way in which society looks at waste management, and there is a growing recycling movement as governments impose stricter limits on CO2 release and more emphasis on what is now known as the circular economy. This is the concept that primary resources should only be used as a last resort and that, where possible, materials should be reclaimed, regenerated and reused.
Green ammonia production is in keeping with the tenets of the circular economy. Taking this a little further, the concept of ‘emerald’ ammonia, or recovered ammonia that comes from the by-products of our own ‘toilette’, using only renewable energy to reclaim it, is now a reality that can incorporate not only the advantages of ‘green’ ammonia production but also the necessity of treating wastewater before it is released to the environment. In that sense its production using this technique could arguably define how the circular economy is designed to function.
In humans, protein breakdown by intestinal bacteria forms ammonia that is converted to urea by the liver, then excreted by our body in the form of urine through the kidneys. It is therefore an important component of wastewater, which then has to be treated to reduce its concentration prior to the water being released back into the environment. Techniques now exist to strip the ammonia from the wastewater and to effectively recycle it.
Of course, wastewater treatment has come a long way since the days of uncontrolled release to rivers, but it is only in the last couple of decades that our waste has been viewed as a potential resource. By treating raw wastewater correctly, it is possible to convert an effluent that has been traditionally seen as an environmental problem into a valuable commodity; something that can contribute both to environmental improvement and a reduction in operational costs, and trials are ongoing to reduce energy requirements and increase productivity, an approach that could make this form of ammonia recovery a truly viable alternative to large-scale industrial fabrication from primary resources.
In recovering ammonia from wastewater, the first step is to collect the water in a lagoon and feed it into the top of a ‘stripping’ tower where gravity causes it to cascade through a column packed with permeable obstacles and through which it trickles; this to ensure that it is thoroughly mixed together with an upward flowing counter-current of air. The ammonia is ‘stripped’ from the wastewater and taken as a gas to its point of use where it can either be destroyed or further processed to produce aqueous ammonia, anhydrous ammonia or ammonium sulphate, a commercially valuable product in agriculture. It can also be collected and used as a medium to produce hydrogen for use in fuel-cells for the production of electricity, another technology that is on the threshold of large-scale deployment as a mechanism to move away from reliance on fossil fuels.
It has been many centuries since our wastewater was chucked out of an upstairs window onto unsuspecting pedestrians walking in the street below. Now it is possible to reclaim just about all of our waste so that the environment can be protected and further benefit can be realised. The production of ammonia from our own wastewater is just the latest example that, if we really want to ensure a future for ourselves and our children, the circular economy must be a fixture in our collective conscience and a way of thinking that should become hard-wired into our daily routine.