How to turn poop into gold

Humans poop a lot. With the world’s population now surpassing 7.4 billion people, dealing with all of this waste is a growing concern for governments around the world. Fortunately, biogas production could one day help offset the resources required to dispose of it properly.

Civil Engineering and Geosciences PhD graduate Dara S.M. Ghasimi, who received his doctorate on April 13th, has spent the past four years researching ways to improve the process. One of the biggest roadblocks engineers are currently facing is how to go about removing foreign particles from human waste in order to turn it into usable biogas. Toilet paper, hair and all sorts of other icky and random things that people flush down their toilets can be tough to filter out. “This material can enter the aerobic sewage treatment plant, adding significant costs to sewage treatment due to energy input for aerobic degradation and incineration costs of the non-degraded fibres that end up in wet waste sludge after digestion,” Ghasimi wrote in his thesis.

This is why agricultural manure is more often used to make biogas. Unlike humans, pigs and cows don’t use toilet paper when they go to the bathroom. Ghasimi’s research suggests that a process that utilises a certain type of fine sieve could filter it and other unwanted materials out of human waste in treatment plants.

The process hasn’t been perfected quite yet and Ghasimi encountered a few hurdles while conducting his research. One was contending with colleagues who weren’t happy about sharing lab space with such a smelly project. A setback a few years ago was particularly unpleasant. “There was a bottle inside the incubator,” Ghasimi said during a presentation before his defence. “I closed the door and suddenly a really big explosion happened.”

Cleaning up the ensuing mess was hardly fun but his research could one day help solve some very big problems. As of 2011, water and wastewater treatment consumed roughly 35% of the energy used by municipal utility services in the United States. Even worse, these facilities used nearly 2% of the country’s total electrical output. If fine sieves could prove to be a cost effective method of converting this waste into biogas, they could help convert these facilities into valuable energy producers.

Ghasimi, D.S.M., Bio-Methanation of Fine Sieved Fraction Sequestered From Raw Municipal Sewage, Promoter: Van Lier, J.B., Defence: April 13, 2016

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