Flush toilets: Essential to civilization, but a break in the nitrogen cycle

Lee Duck-hwan

The author is an honorary professor at Sogang University.

Korea’s restrooms are evolving rapidly. The transformation of public toilets in parks, open around the clock and free of charge, is especially striking. As part of preparations for the 1988 Seoul Olympics and the Korea-Japan FIFA World Cup 2002, once-dirty public bathrooms became remarkably clean and hygienic. Not only is the presence of toilet paper standard, but many restrooms also offer hot water and air conditioning. Accessibility has improved dramatically as well. These facilities are good enough to be promoted proudly as “K-toilets.”

The real transformation began in the 1970s with the spread of flush toilets. Since then, traditional pit latrines and night-soil trucks dependent on manual labor have virtually disappeared. Toilet paper became a household necessity, and squat toilets gave way to more comfortable Western-style toilets. Now, many homes are even installing bidets.

Modern urban life would be impossible with toilets that store human waste, as the odor and unsanitary conditions of traditional latrines would be intolerable in high-rise buildings. But toilets have always posed a challenge throughout human history. In traditional Korean homes, the outhouse was an undesirable facility kept apart from living quarters, rendering portable chamber pots unavoidable.

Conditions in the West were not very different. In medieval Europe, chamber pots were routinely emptied into streets, leaving cities badly contaminated by human waste and foul smells. People supposedly used parasols to block waste falling from buildings, high heels to avoid stepping in filth and perfume to mask the surrounding stench. Vendors also offered privacy behind a leather cloak, or toile, for people relieving themselves in the street. The word “toilet” is said to have emerged from such practices.

Yet flush toilets have a surprisingly long history. Systems using naturally flowing water appear to date back to around 3000 B.C., although that kind of luxury was never available to everyone. In Korea, traces of a royal flush toilet with a granite seat were discovered at the Donggung Palace and Wolji Pond site in Gyeongju, dating to the Unified Silla period (668-935).

Modern flush toilets, developed in earnest from the 18th century, were not an immediate success. Contaminated water sometimes flowed back into homes with the tide, and summers brought serious algal blooms and waterborne disease. In the early 19th century, sewage discharged from toilets severely polluted the River Thames. Septic tanks for treating toilet waste were developed in response in the mid-19th century.

In Korea, separate sewer systems that distinguish wastewater from rainwater and terminal sewage treatment plants began appearing in the late 1980s. Such infrastructure, of course, requires enormous expense and effort.

Natural ecosystems survive by recycling elements, including carbon, nitrogen, oxygen and phosphorus. Plants capture atmospheric carbon dioxide through photosynthesis and turn it into carbohydrates. Animals consume those carbohydrates, then release carbon dioxide back into the air. This carbon cycle is fundamental to sustaining ecosystems.

The nitrogen cycle is equally important. Nitrogen is a core component of proteins, which regulate physiological functions, and of DNA and RNA, which carry genetic information. As a result, humans and other animals must consume sufficient protein containing nitrogen. Nitrogen-fixing bacteria living in nodules on the roots of legumes and lightning generated by thunderstorms provide natural starting points for nitrogen circulation.

Human waste is also an important link in that cycle. Nitrogen absorbed through protein returns to nature in urine and feces, helping plants grow. Asian societies actively used this knowledge to turn human waste into fertilizer.

Waste flushed into modern toilets, however, cannot readily return to terrestrial ecosystems. Nitrogen compounds broken down in septic tanks or sewage treatment plants eventually travel through rivers into the sea. The problem is even more serious when sewage is dumped directly into international waters. Once nitrogen is carried far offshore, its return to productive land ecosystems becomes nearly impossible.

Flush toilets are indispensable for clean, healthy urban sanitation, but they also interrupt nature’s nitrogen cycle. The result may be a serious decline in the total biomass that ecosystems can support.

Modern civilization must solve the disruption it has created. Since human waste can no longer be collected and spread on fields as it once was, urea fertilizer made by reacting atmospheric nitrogen with hydrogen extracted from natural gas or coal has become indispensable to food production.

Many people denounce chemical fertilizer as inherently harmful. But enjoying the convenience of flush toilets while refusing to bear their ecological cost is irresponsible. Convenience always carries a price.

Those who reject chemical fertilizer should at least be willing to separate urea from their urine whenever they use a toilet and send it to farming communities. Since that is unrealistic, society must recognize why chemical fertilizers exist and work intensively to use them more safely and efficiently without sacrificing sanitation, productivity or environmental responsibility.