Over the past century, the human population has increased by nearly 6 billion people (FAO, 2000). In order to support the growing population, agricultural practices have become increasingly intensified to produce a greater quantity of food from a relatively equal amount of land (FAO, 2000). The increased production can be contributed to many developments of the global agriculture industry, including the greater density cultivated livestock and the use of fertilizers (FAO, 2000). The high density of animals in modern livestock operations has created a concerning excess of animal waste and is predicted to double within the next thirty years (Zarebska et al., 2015; Ilea, 2009). Nearly 500,000 tones of manure are produced every day from livestock operations across Canada, which generates about 180 million tones of waste each year (Statistics Canada, 2006). Manure can serve as an abundant source of essential plant nutrients; however, the volume of manure generated by modern livestock operation is beyond a sustainable capacity (Zarebska et al., 2015).
It is critical that an alternative management practice for manure is implemented in order to minimize the repercussions that can be expected from the increasing production of manure (Alberta Agriculture, 2004). The livestock sector accounts for the greatest portion of air pollution that results from human industry, accounting for nearly 18% of all greenhouse gas emissions (Ilea, 2009). Manure from livestock operations has been estimated to contribute 68% of all nitrous oxide from human origin (Ilea, 2009). Many known environmental impacts have been determined to originate from the overabundance of raw manure (Alberta Agriculture, 2004). The storage and application of excess manure generates harmful greenhouse gases, such as methane and nitrous oxide (Alberta Agriculture, 2004). For example, the common practice of storing unusable manure under anaerobic conditions results in a very low level of nitrogen (FAO, 2000). Anaerobic bacteria quickly degrade the nitrogen present in manure during storage and with minimal or no vegetation present to use the compounds released, the valuable source of nitrogen is lost to the environment (Milin, Artists, Innovators & Visionaries Episode 11). The loss of nitrogen is concerning because the composition of nutrients in the manure is altered, which causes further pollution. While the bacteria that develop in the manure during storage quickly alter the nitrogen compounds, the phosphate remains unchanged. Milin explains that farmers apply an excess of manure to accommodate for the low levels of nitrogen and as a result apply a concentration of phosphorous beyond the requirement of crops. Certain management techniques have been developed to reduce emissions from stored manure (Alberta Agriculture, 2004). However, no solution has been implemented that completely eliminates the air and water pollution from animal waste. The nutrient content of manure is generally not sufficient for modern agriculture to generate the necessary yields. Therefore, fertilizer is understood to be a necessary input for efficient agricultural production (FAO, 2000). Fertilizers, either from a natural or chemical source, allow farmers to maintain intensified production without depleting the land (FAO, 2000). As the Earth is no longer able to naturally support the quantity of food required by the dense human population, chemical fertilizers are commonly used (Smil, 2001).
The development of synthetic fertilizers has allowed for a greater increase in the productivity of agricultural land. Global agricultural production relies on chemical fertilizers to feed an estimated 40 to 60% of all food products (Zarebska et al., 2015). Smil (2001) suggests that the Haber-Bosch creation of synthetic nitrogen fertilizer can be understood to have allowed the increase in production that was necessary to support growing population. Today, we rely on the Haber-Bosch process to supply approximately half of all synthetic nitrogen that is required to meet production demand (Smil, 2001). The Food and Agriculture Organization of the United Nations estimated that approximately 40% of protein consumed around the world in the mid-90s originated from nitrogen synthesized by the Haber-Bosch process, which uses atmospheric nitrogen and natural gas (FAO, 2000).
The global population is expected to rise beyond 9 billion by the year 2050, which will require a further increase in the quantity of food produced from agricultural land (Zarebska et al., 2015; FAO, 2015). Considering the modern dependence on fertilizer to meet production demand, fertilizer use will have to increase to sustain a greater quantity of food returned from production (FAO, 2015). Shaviv and Mikkelsen (1993) estimate that half of all nutrients supplied from synthetic fertilizer are lost to the surrounding environment as ammonia, nitrous oxide and other nitrogen compounds. The significant leaching of nutrients is polluting the land in the form of water and air pollution (Zarebska et al., 2015). Excess nitrate that escapes from fertilizer has collected in soil, groundwater reservoirs and bodies of water surrounding cropland (Savci, 2012). Nitrate pollution is of great concern due to the severe health implications of water containing an excess of the compound (Sahviv and Mikkelsen, 1993). To maximize the low efficiency of current fertilizer sources, the agriculture industry should increase the use of fertilizer available in a slow-release form, where nutrients are steadily supplied to plants over time (Sahviv and Mikkelsen, 1993). Despite the proven advantages to supplying nutrients to crops in a controlled manner, the proportion of controlled-release fertilizer compared to fast acting sources is minimal (Sahviv and Mikkelsen, 1993). The use of slow-release fertilizer is mainly restricted to becoming a common practice due to the high cost (Sahviv and Mikkelsen, 1993).
It is estimated that around 90% of the increased food production required for the rapidly growing population must be generated from agricultural land currently under production (FAO, 2000). Current management practices regarding the surplus of manure and the use of fertilizers has contributed to environmental damage that could reverse the associated benefits of supplying extra nutrients. Fertilizer development around the world has allowed a successful increase in crop yields but has caused environmental damage. Therefore, it is critical that a sustainable and efficient source of fertilizer that will not cause further harm be developed for global agricultural use.