And if our excrement could make ride the bus?

Hélène Roulot-Ganzmann

Special Collaboration

April 18, 2020

Et si nos excréments pouvaient faire rouler des bus?

The researcher Rajeshwar D. Tyag in front of the facilities for the bioconversion of sewage sludge and wastewater

This text is part of the special Earth Day

The sludge, whether they are urban or industrial, are the main waste produced by a wastewater treatment plant from waters discharged by the drains. These sediments waste are primarily composed of organic matter, i.e. dead bacteria, and organic matter are animal, vegetable and mineral.

Rich in nitrogen and phosphorus, these sludges are widely used as a fertilizer, especially in Europe, by the agricultural industry. They, however, can contain heavy metals. Thus, in the United States, the spreading of slurries is practiced for more than 30 years in the forest, is suspected to be the cause of some pollution and the onset of degenerative diseases affecting an increasing number of deer in a dozen States and Canada.

In other words, properly used, this sludge can be very valuable, but they also constitute a double-edged sword. However, an installation moyennede management of wastewater to produce about 40 grams of sludge dehydrated by day and per capita. Either at the scale of Quebec’s population, more than 124 000 tonnes per year, just for sludge, domestic. A veritable windfall !


This is the number of grams of sludge dehydrated the average plant management of the wastewater produced daily per capita.

Technology transfer

Two professors of the Institut national de la recherche scientifique (INRS) have thus had the idea of developing a biodiesel from these sewage sludge.

“The idea is to add to the slurry, primarily municipal or derived from the pulp and paper industry, an organic compound which participates in the development of fats, namely glycerol,” says Rajeshwar D. Tyagi, a researcher in bioconservation of residues and co-lead scientist of the Laboratory of environmental biotechnologies (LBE) to INRS.

“Then we place this mixture in the presence of microbial organisms that will feed on the sludge and transform it into a biomass, cellular lipid-rich. “

Once this bioréaction is complete, the biomass is recovered and its cells broken with a biodegradable detergent manufactured by the LBE. The lipids that are found inside the cells can then be captured, optimized, and converted into biodiesel.

With his colleague Patrick Drogui, a researcher in électrotechnologies and water treatment, Mr. Tyagi is working on the development of the process of transformation since 2011. Their work has also garnered numerous awards scientists around the world. Today, the team went all the way to her laboratory research, she is ready for the transfer of technology to industry. The process will thus soon be tested in pilot plants before they reach the market.

“There is still a long way to go, warns, however, professor Tiagy. We don’t know what will happen once the process led to large-scale. In the laboratory, we do not gather that twenty litres of bio-diesel in our tanks. Here, we speak of tons of mud and thousands of litres of biodiesel. “

“Food for fuel “


If the production of biodiesel by the LBE is still in its experimental phase, the laboratory can boast of having already managed to transform the sludge into other bioproducts. The activities of the laboratory are focused on obtaining value-added products using the discharges of municipal, industrial or agricultural as a base substrate. The work portentnotamment on the production debiopesticides microbial and fungal inoculants microbial, growth promoters vegetable, industrial enzymes, bioplastics and other biopolymers, and biofuels. Some processes are already on the market.

“We have good reason to believe that our biodiesel will be also, says Rajeshwar D. Tyagi. First, because the capacity of our laboratory enables us to have a first scale, intermediate, prior to testing in the pilot plants. Then, because the process used for bioplastics is much the same, and we already know that it works well. “

At a time of climate change, biofuel demand is strong, and some countries have begun to impose a minimum share of biofuels in fuel consumption. This regulation, however, presents problems, particularly in terms of food security.

In addition to reducing the generation of greenhouse gases — caused by the landfill of this sludge by municipalities and industry, the production of biodiesel from sewage sludge rule, and the dilemma of ” food vs. fuel “, that is, the use of arable land for biofuels at the expense of food production.

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