Each year, the United States produces 110-150 million metric tons of sewage sludge. A large portion of this waste is deemed unusable, deposited into landfills, and left to decompose. This ultimately produces toxins that contaminate drinking water, air, and has countless other harmful effects on the environment. But, this issue can be avoided by incorporating sewage composting, or the process of converting human sewage waste into fertilizer, into our city’s municipal sewage treatment system. This innovative alternative should be implemented as it is a practical and economical solution that takes otherwise “useless” human waste and transforms it into valuable, high yield fertilizer that is highly nutritional to plants, and environmentally friendly.
The process of sewage composting is not complicated, and can be incorporated easily into existing sewage treatment procedures. By utilizing human waste to create fertilizer, the process offers a practical and reasonable alternative to landfilling. This transformation consists of two main phases: thickening/dewatering and composting. The first phase, thickening, uses clarifiers to form larger particles of solids in the sludge. Then, a centrifugal process uses rapid rotation to separate solids from liquids and dewaters the sludge, reducing it to a solid containing approximately 50% water. This is already part of regular sewage treatments; however, it still contains many contaminants such as heavy metals, and pathogenic substances. The second phase, composting, uses naturally occurring microorganisms to remove said contaminants, and it converts the organic waste into a fertilizer. During composing, the sludge is mixed with bulking agents that contain large quantities of carbon (sawdust, wood chips); these agents will reduce the water content. Then, aerobic thermophilic microorganisms, usually Bacillus Stearothermophilus strains, utilize the material to grow and reproduce. Due to decomposition, temperatures rise to 55-75°C (hence the name thermophilic- “heat loving”) which is in the pasteurization range, thereby eliminating any pathogenic microorganisms. The resulting product is a soft, humus-like material (called “biosolid”) which can then be compacted into pellets or freely applied to land.
A possible concern with implementing sewage composting would be the presence of heavy metals in the biosolids. Current methods to remove these metals can be expensive, and highly ineffective. But, this concern can be addressed by treating the biosolids with acids. Using hydrogen peroxide and phosphoric acid, heavy metals such as copper will be removed from the sludge, leaving only trace amounts that do not affect any plants when put into the soil. This is a pioneering improvement to the waste-fertilizer process that will greatly decrease the problems associated with heavy metals in plants.
The current price for nitrogen fertilizer is approximately $504.00 per ton. This can be exceedingly expensive for farmers, since they apply fertilizer to several acres of land. Using human biosolid fertilizer aids in solving this problem, as it can be sold at a much lower price, while still making a profit. Since municipal sewage is very abundant and is essentially unlimited, large quantities of biosolid fertilizer can be produced. The treatment is low cost in comparison to the production of commercial fertilizers; composting is mainly just an extension of treatment, and doesn’t require high levels of electricity or other expenses. The fertilizer can be mass produced at a low cost, benefiting the manufacturer of the product, and taxpayers in municipalities. Thus, it can be sold at a lower price (while still gaining profit). Now, the farmers can focus their income on increasing the quality of the crops rather than wasting money on overly priced fertilizer. Basically, it’s a win-win situation for the consumer and maker. Therefore, implementing the use of human biosolid fertilizer can be very beneficial to the economy as well as individuals.
Contrary to popular belief, human biosolid fertilizer has high concentrations of nutrients, such as nitrogen, phosphorous, and potassium. The most common deficiency in soil is nitrogen; although nitrogen fertilizers are available and commonly used, their production requires large amounts of energy. In a recent study done at the University of Nebraska-Lincoln, several sites were treated with nitrogen fertilizer or sewage sludge fertilizer; the grain yield of each site was used to compare the effect of the two fertilizers. The study concluded that while there was little response to normal nitrogen fertilizer, locations receiving high rates of biosolids yielded more crops. In addition, biosolids provide sulfur and magnesium, which are essential in plants’ ability to photosynthesize. These nutrients are less soluble than artificial fertilizers, which means they last in soil for longer periods of time. They are less subject to leaking into ground water, resulting in less pollution of waterways. Despite the rigorous treatment process that sewage had to go through, some may argue that along with the nutrients comes harmful bacteria that can destroy crop yields. But this is false, since biosolids are not known to produce or spread diseases when handled properly. Also, the sewage sludge goes through extensive treatment that complies with the strict regulations imposed by United States Environmental Protection Agency (EPA).
Landfilling is the most common method of waste management, and one of the worst as well. It causes large amounts of pollution, including leachate, greenhouse gases, and toxins. Leachate is produced when rainwater flows through the garbage producing a rancid suspension; this leaks into groundwater supplies, causing water pollution. Landfills also cause atmospheric pollution - and incredibly revolting odor. By using sewage composting, these effects can be avoided, since the waste would no longer rot in landfills. One may argue that the biosolids have strong odors, but the process of aerobic digestion greatly reduces the odors. Human biosolid fertilizer increases the quality of the soil, so fewer quantities are required in consecutive crop cycles. The EPA states that the application of biosolids decreases dependency on herbicides and pesticides in this quote: “The changes that occurred because of biosolids usage allowed the farmer to decrease his costs for fertilizer, herbicides, and pesticides...” (EPA, 13). These changes allow plants to better compete with unwanted invaders, decreasing their dependency on chemicals. It’s obvious that the use of sewage composting to produce biosolid fertilizer is beneficial to the environment.
I propose that our city should implement the process of sewage composting, as it has numerous benefits. If we miss this opportunity, our landfills will continue to grow, and we would be guilty of polluting our beautiful planet. Taking this step will put us in the forefront of the green city movement. Sewage composting is useful, and is beneficial to the environment, economy, and our crops; it is ultimately a solution, that takes the stink away from sewage!
References:
“2017 Infrastructure Report Card.” 2017 Infrastructure Report Card, ASCE, 2017 Infrastructure Report Card.
“Utilization of Sewage Sludge Compost as a Soil Conditioner and Fertilizer for Plant Growth.” Https://Pdfs.semanticscholar.org/, United States Department of Agriculture, https://pdfs.semanticscholar.org/11a6/efae934a92ea43c6079d92f4e15992775aa0.pdf
“Fact Sheet: Sewage Sludge Use and Disposal Rule (40 CFR Part 503).” EPA, Environmental Protection Agency, Nov. 1992, nepis.epa.gov/.
University of Nebraska-Lincoln | Web Developer Network. “Sewage Sludge vs. Nitrogen Fertilizer (Research).” Sewage Sludge vs. Nitrogen Fertilizer (Research) | Nebraska Extension in Lancaster County | University of Nebraska–Lincoln, D.L. Binder and D.H. Sander, D.L. Binder and D.H. Sander, lancaster.unl.edu/enviro/biosolids/research.shtml.
Dring, Rachel. “Human Manure: Closing the Nutrient Loop.” Sustainable Food Trust, 15 May 2015, sustainablefoodtrust.org/articles/human-manure-closing-the-nutrient-loop/.
“Biosolids Recycling: Beneficial Technology for a Better Environment.” EPA, Environmental Protection Agency, nepis.epa.gov/.
Yoshizaki, Shiro, and Tahei Tomida. “Principle and Process of Heavy Metal Removal from Sewage Sludge.” ACS Publications, Mar. 2000, pubs.acs.org/doi/abs/10.1021/es990979s?journalCode=esthag.