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Beware the Latrines; An Unexpected Source of Energy

It was not uncommon for Romans to have a painting of Fortuna the goddess of chance in their latrines, or toilets as they are referred to nowadays. They would pray to her that things would go smoothly – but what could go wrong in a latrine?

Although toilets may not be the first thing that comes to mind when thinking of Ancient Rome, they might have had an explosive nature back in the day that made users of the latrines take special caution when carrying out their business. This fear of toilets has been inferred from the lack of graffiti and the abundance of portraits of Fortuna, the goddess of chance, in the latrines. But what might have made members of this ancient, often ruthless, civilization so scared of holes in a bench? Archeologist Ann Koloski-Ostrow speculates that the build-up of mechanic gases in the sewers underneath the toilets could have led to flames inside the toilet. That is not something one wants to encounter with their pants down!

Due to the enclosure of human waste in a low-oxygen environment, latrines were likely an ideal place for the production of what is now more commonly known as sewer gases. Sewer gases are the side-product of a process known as anaerobic digestion in which bacteria break down organic products. Major components of sewer gases include methane and hydrogen sulfide. While the latter has a characteristic rotten egg smell, the former is odorless and colorless. Both of these gases are highly flammable.

Current-day sewer systems have many mechanisms in place to prevent the build-up of sewer gas. However, in Ancient Rome the latrines and sewer systems did not meet modern standards as, from the archeological evidence, they seem to have lacked proper ventilation, flow, and maintenance. This means that more likely than not, the methane and hydrogen sulfide gases would build up to sufficiently high levels that they could catch on fire, or potentially cause an explosion.

Interestingly, some civilizations decided to take advantage of this explosive energy source; the Assyrians in 3,000 BC were thought to use these gases to heat their baths. Since then, the production of these flammable gases through the anaerobic decomposition of organic matter has become a source of energy known as biogas.

Biogases consist mainly of methane and carbon dioxide and can be used as vehicle fuel or a replacement for natural gas known as Renewable Natural Gas (RNG). This means that biogas is highly versatile and can be used to produce renewable heat and electricity, and can be stored to later power things like transportation, and household heating. The use of these gases as an energy source also prevents the sewer gases from reaching the atmosphere and contributing to greenhouse gas emissions.

The primary sources of biogas are organic material from agriculture such as livestock manure and crop residues, compost from households and businesses, landfills, and biosolids from wastewater treatment such as feces. WRAP, a climate action NGO, predicted that the UK’s households, hospitality and food service sectors, food manufacturers, and retail and wholesale sectors produce around 10 million tonnes of food waste per year which if treated through anaerobic digestion could generate 11 TWh of biogas; this would be sufficient to heat 830,000 homes,

When I came across the tale of explosive latrines in Ancient Rome, I never would have thought it would be tied to a renewable energy source that we can use to reduce our carbon dioxide emissions – but I guess that’s the beauty of science!


@DanielaPadres

Daniela is a recent B.Sc. graduate from the program of Physiology at McGill. She is very passionate about understanding the human body and how we can all individually adapt our daily lifestyles to improve its functioning.

Part of the OSS mandate is to foster science communication and critical thinking in our students and the public. We hope you enjoy these pieces from our Student Contributors and welcome any feedback you may have!

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