Society's Grand Challenges. A simple introductory freshman class assignment.

            

The challenges facing society today are many in number and great in difficulty. We live in a world beset on all sides by the threats that climate change, pollution, disease, poverty and many more. In almost all cases it was humanity’s great strides in technology and knowledge that caused these problems and in the 21^st century it shall be our advances in such fields that solve these grand challenges. The role of the engineer will be paramount in each sector, and chemical engineers will be in a unique position. The most talked about and important challenge is of course climate change due to global warming and emission of CO₂, a problem that involves a fair amount of chemistry will need a chemical engineer to solve it. There is another situation that has both been one of humanity’s greatest achievements and, as current research now begins to show, one of the most polluting elements introduced to the Earth. That element is nitrogen. Without nitrogen the Green revolution never would have occurred, but its overuse has contributed to many of the grand challenges we face today.

            The problem isn’t that nitrogen is overly toxic to life, it makes up 78% of the air we breathe, 3% of our own bodies and is essential to all legumes in the world; the problem is the way it’s been used so extensively and carelessly. Fritz Haber discovered the way to transform the abundant nitrogen gas in the atmosphere into ammonia in 1909 and 20 years later Carl Bosch developed the industrial scheme commonly known as the Haber-process, this transformed the agricultural landscape. Factories started churning out ton after ton of ammonia-based fertilizer and the global population skyrocketed from 1.6 billion to 6 billion in one century. One of the most significant advancements in public health has come with a high price as most of the reactant nitrogen that is made, both as fertilizer and from the combustion of fossil fuels does not make it into the food we eat. It runs off into the rivers and streams or into the atmosphere where it causes both ozone depletion and global warming. The algae blooms that are an everyday sight cause coastal dead zones as all the oxygen its absorbed, and new indications are pointing at nitrogen as a contributor to a higher incidence of deadly human diseases like malaria and Schistosomiasis.

            The nitrogen cycle that is causing problems starts when the nitrogen produced during fossil fuel combustion combines with water in the atmosphere to form nitric acid rain. This then joins the nitrogen runoff from over fertilized farms and human/animal waste in streams and rivers which feeds microscopic plants. These plants consume oxygen as they decompose forming dead zones. The excess nitrogen is also limiting biodiversity. When its added to a plant, the plant grows, but when excess nitrogen is added to a plant that isn’t used to an environment so rich in nutrients, other plants grow faster, killing off the weaker one. A normal person might not care if a rare plant dies, but new research is showing that elevated nitrate concentrations in drinking water can cause cancer, multiple heart problems, Alzheimer’s and diabetes. In the atmosphere reactive nitrogen combines to form ground-level ozone as nitric oxide or nitrogen dioxide. These compounds are both a significant greenhouse gas and extremely damaging to plant tissues, resulting in the loss of billions of dollars in crops each year. When it forms N₂O it becomes the most powerful greenhouse gas, 300 times more so then a molecule of CO­_2. Its concentrations in the atmosphere represent the equivalent to 10% of CO₂ contribution.

            The challenge in this case is just how essential reactive nitrogen has become in our society. Without fertilizers the world would never be able to support its current population, and nitrogen aerosols counteract global warming by reflecting incoming radiation. 400 billion pounds of reactive nitrogen is produced annually, twice the amount naturally produced by nitrogen-fixing bacteria and volcanoes. So what technological advances can limit the negative effects while boosting the positive?

            The first step would be to eliminate the excess reactive nitrogen produced by the burning of fossil fuels. The use of NO_x scrubbers in smokestacks could reduce emissions greatly. A much more effective tool at removing nitrites and nitrates from waste water is through the use of biological synthesis and nitrification, ion exchange, air and steam stripping and chlorination. These processes make use of natural aerobic bacteria to decompose ammonia and other compounds found in waste water. This process is useful when dealing with animal and human wastes but the effects of over fertilization are harder to manage from a chemical engineering standpoint. Current research into much more effective fertilizers and the delivery system to the plants roots is the most promising in reducing the nitrogen pollution. Current views on fertilizer are more is better, but with the new methods of delivery, denoted the 4R’s; right source, time, rate and place, the need to use excessive amounts is diminishing.

            Chemical engineering paved the way for the production of 400 billion pounds of reactive nitrogen each year and its usage has greatly improved the quality of life for billions of people, but its negative aspects must also be addressed by chemical engineering in the future. Advancements in fertilizers and farming techniques will go hand in hand to solving this problem. Along with new treatment facilities using nitrification, suspended growth systems and ion exchange systems can prevent the nitrogen compounds from entering municipal water supplies. Unlike the problem of CO₂ emissions, we can’t just stop the usage of nitrogen. This is why it’s an even greater challenge for society to face because it is so essential to the survival of our current populations. One of the easiest ways chemical engineering could help solve this problem is to produce effective fertilizers cheaper, so that poor countries stricken by famine can feed their populations, while rich nations limit the use of fertilizers and instead make use of genetically engineered crops resistant to disease.  Solving the grand challenges of air pollution, water pollution, global warming, poverty, and quality of life will require society to critically evaluate the current use of nitrogen if a sustainable use of the chemical in the future is possible.

References:

1)      Adams, E Carl Jr. “Removing Nitrogen from Waste Water”  Environ. Sci. Technol., 1973, 7 (8), pp 696–701

2)      Howarth, Robert W., Townsend, Alan R. “Fixing the Global Nitrogen Problem”

Scientific American February 2010.  64-71