Elements: The Full Story

I was very engaged by this week’s readings on phosphorus. As a senior chemistry major, I have encountered many theories about the structure and interactions of a wide range of elements in various situations. Most chemistry classes, however, view the world through a rather abstract, decontextualized lens. We learn many reactivity details, and often the technological applications of these phenomena, but we rarely look beyond chemical suppliers for the origins of the elements we manipulate.

 For this reason, I have really liked learning about global element cycles, the ways humans impact these cycles, and why they do so. In chemistry classes, we label many reactions as “industrially relevant,” which means people will pay you to do them, but we don’t often discuss the motivations or global ramifications of such transformations. I have really liked seeing data on how elements move naturally through the environment, and which industries manipulate them on what scale.

 In general, I have found that environmental context becomes more relevant in real-world chemistry research. I spent two summers researching the chemical origins of life on earth, which invoked many questions of paleoclimate and paloegeochemistry. When life started forming billions of years ago, it had to work within the constraints of which elemental building blocks existed in significant quantities on earth. As the Elements article states, phosphorus was indeed an odd choice, though I didn’t realize until now the actual degree of its scarcity[1].

 Our arsenic readings have also been fascinating, because they highlight the weakness of human biology in its susceptibility to something in such abundance on planet earth. Understanding arsenic intolerance in humans adds to the novelty of a recent report from a California astrobiology lab of bacteria that could actually replace phosphates with arsenates in many biomolecules[2]. Lead author Felisa Wolfe-Simon comments that “toxicity is in the eye of the beholder[3]”.   I find this a useful phrase to remember when considering environmental hazards to biological systems. It makes me wonder more about the arsenic distribution at the time when life was first evolving. Did a lesser presence possibly contribute to our apparent lack of defenses against exposure?

Returning, though, to human interaction with the global phosphorus cycle, I was primarily intrigued by the “story of phosphorus” article[4]. The most important use of phosphorus is fertilizers for food production. Excreta and decaying organic matter were the original phosphate sources. Bird and bat droppings provide a particularly good source, which I first discovered while visiting Carlsbad Caverns, NM this summer and learning of early mining operation there. I didn’t realize, though, that such droppings constituted a major global source.   A better grasp of bio and geo chemistry led to the utilization of mineral sources like rock phosphate. Current world reserves are concentrated in China, the US, and the Western Sahara[5].

I was startled by the estimation that only 50-100 years of global reserves exist. First, I never realized phosphorus was a non-renewable resource. I assumed that, like nitrogen, it was fairly available, but I guess that is only true because atmospheric abundance and the development of the Haber process for artificial fixation. Aside from eutrophication, I have never encountered any concern over phosphorus depletion. I was surprised again to learn that no coherent organization exists for the monitoring and management of the overall phosphorus cycle.

The article offers several approaches to prevent disastrous phosphorus depletion. First, some have suggested more aggressive exploration and exploitation of the planet for potential reserves. This however, produces dangerous byproducts, consumes large amounts of energy, and only offers a short-term solution. A more viable option involves the recycling of waste. Since close to 100 percent of consumed phosphorus is excreted, we can potentially recycle all that we need[6].

This solution, however, is greatly impeded by the aforementioned lack of cohesion in phosphorous management. Modern sanitation systems are not designed for any significant waste reclamation, so extensive changes would have to occur in that sector. The primary challenge is separating nutrients from the chemical and biological hazards that also exit our bodies. Urine is the easiest type of waste to manipulate, and also the safest. A promising case study from Sweden shows that it can be safely stored for significant time periods and used as fertilizer with reasonably simple domestic waste engineering[7].

The last approach is to simply reduce demand. Certain food types require more nutrient input than others. One convincing statistic is that meat eaters require nearly three times the phosphorus inputs of vegetarians. Nutrition should also be considered in our alternative fuel choices, since biofuels will definitely add to the phosphorous burden. Agricultural techniques are another important consideration. Organic techniques and careful monitoring to apply phosphorus only where needed are two strategies that will increase sustainability[8].

I am struck by the parallels between phosphorus and energy conservation. They both require alternative, more difficult sources coupled with a reduction in demand. Multiple approaches exist for these two goals in each sector. I think this highlights a fundamental law of nature that is crucial to our survival as species. Basically, we can never avoid the finite nature of our planet. If we must consume, we must mitigate this consumption in every way possible. We can’t rely on a technological silver bullet in one part of the system to erase the problem. The connectivity of the natural world simply doesn’t allow it, so we have to educate everyone until they can understand the world on a comprehensive scale. 

 

                 

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[1] Filippelli, G. (2008, April). The global phosphorus cycle: Past, present,
future. Elements, 4, 89-95. doi:10.2113/gselements.4.2.89

[2] Wolfe-Simon, F., Blum, J., Kulp, T., Gordon, G., Hoeft, S., & Stolz, J. (2010,
December 2). A bacterium that can grow by using arsenic instead of
phosphorus. Science Express, 1-9. doi:10.1126/science.1197258

[3] Flatow, I. (Speaker). (2010). Talk of the nation. NPR. Retrieved from
http://www.npr.org/2010/12/03/131785452/
Arsenic-Eating-Bacteria-Challenge-View-Of-How-Life-Works

[4] Cordell, D., Dragert, J.-O., & White, S. (2009). The story of phosphorus: Global
food security and food for thought. Global Environmental Change , 19,
292-305. doi:10.1016/j.gloenvcha.2008.10.009

[5] Cordell, D., Dragert, J.-O., & White, S. (2009). The story of phosphorus: Global
food security and food for thought. Global Environmental Change , 19,
292-305. doi:10.1016/j.gloenvcha.2008.10.009

[6] Cordell, D., Dragert, J.-O., & White, S. (2009). The story of phosphorus: Global
food security and food for thought. Global Environmental Change , 19,
292-305. doi:10.1016/j.gloenvcha.2008.10.009

[7] Cordell, D., Dragert, J.-O., & White, S. (2009). The story of phosphorus: Global
food security and food for thought. Global Environmental Change , 19,
292-305. doi:10.1016/j.gloenvcha.2008.10.009

[8] Cordell, D., Dragert, J.-O., & White, S. (2009). The story of phosphorus: Global
food security and food for thought. Global Environmental Change , 19,
292-305. doi:10.1016/j.gloenvcha.2008.10.009