Consequences of Urea

Urea is an inexpensive form of nitrogen fertilizer with an NPK (Nitrogen-Phosphorus-Potassium) ratio of 46-0-0. Although urea is naturally produced in humans and animals, synthetic urea is manufactured in a factory when carbon dioxide is reacted with anhydrous ammonia. This is an extremely intensive process that requires high amounts of natural gas and happens under intense pressure, at 350 degrees Fahrenheit (see Figure 1 below). Urea is processed to take the form of granules or solid globules known as prills. 

Urea is the most common chemically based fertilizer in the world today and requires huge amounts of natural gas to be manufactured. Urea can be used in the manufacturing process of glue, resin, plastic, formaldehyde, cigarettes and adhesives but, more than 90 percent of world urea production is destined for use as a nitrogen-release fertilizer. Ammonia plants consume about 1 percent of global energy; 1 percent of global energy goes towards creating a harmful substance that is only a short term solution to infertile soil and makes the soil continue to increase in infertility and dependency on external fertilizers. Even worse, most of the food grown with the help of urea is decreasing in nutritional value and is used as feed for the animal agriculture industry.

Chemically based nitrogen fertilizers account for ⅔ of the carbon footprint of crop production. When coal- and natural gas–fed plants produce ammonia, they generate two main by-products: heat and carbon dioxide (CO2). Even high-efficiency ammonia plants are heavy CO2 emitters; two tons are released for every ton of ammonia produced. In 2011 U.S. ammonia-producing facilities released 25 million tons of greenhouse gases (nearly all of it CO2)—just under 14 percent of the chemical-manufacturing sector’s total carbon footprint (and about 0.1 percent of total U.S. emissions). Globally, ammonia production represents as much as 3 to 5 percent of carbon emissions, according to some industry sources. And that doesn’t take into account the supply chain of natural gas production, energy-related emissions in the production process, fertilizer application (and misapplication) or industrial use of urea and other ammonia products.

One ton of urea will emit about 0.73 tons of CO2, but its carbon footprint, derived through a full life-cycle analysis, will be closer to 5.15 tons CO2-equivalent (CO2e). So the carbon contained in urea represents only about 14% of its total carbon footprint – the bigger issues are energy, used in production and transport, and emissions of N2O, which is 296 times as potent as CO2. The disappointing fact is how much of the urea that is manufactured and applied to farmland is completely wasted. Rhykka Connelly, PhD, from the University of Texas at Austin wrote an article on How Algal Biofertilizers Can Accelerate Sustainable Agriculture and she stated that “On average, 5.5 gallons of fossil fuels per acre, per year are needed to fertilize soil for farming. Another way to state this is that the average U.S. farm uses three kcal of fossil energy to produce one kcal of food energy. Ironically, it is estimated that crops actually absorb only one-third to one-half of the nitrogen applied to farmland as fertilizer”.

So, it takes immense amounts of energy and natural gas to manufacture a harmful chemical with a huge carbon footprint, that is supposed to help plants grow but, less than half of the urea is ever absorbed and the rest is left to poison watersheds and local ecosystems. It has become abundantly clear that the issues caused by urea production do not outweigh the small benefits that it has to offer; switching to a better alternative is necessary.

 

For more information on urea check out these links:

https://sustainability.utexas.edu/pssc/symposium/2011/16

https://ammoniaindustry.com/urea-production-is-not-carbon-sequestration/

https://www.scientificamerican.com/article/fertilizer-plants-grow-thanks-to-cheap-natural-gas/