Gypsum boards should be easy to recycle. However, this is not the case in practice. A researcher from Laval University found a solution: replace the gypsum with… earth.
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The process developed by Laval University makes it possible to use “raw” earth, that is to say unheated, rather than gypsum, a mineral which must be heated to very high temperatures in the first stage of the process, called calcination.
“We are removing the step at the start of panel production, which consumes a lot of energy,” explains Pierre Blanchet, an engineer specializing in wood at Laval University, who publishes his results in the journal Construction and Building Materials.
PHOTO PASCAL RATTHÉ, SPECIAL COLLABORATION
Researcher Pierre Blanchet, engineer specializing in wood at Laval University
In theory, gypsum panels are recyclable, but in reality, they rarely are and are sent to landfill with various construction waste, according to Mr. Blanchet. A panel is made of gypsum that has been subjected to calcination, enclosed between two sheets of paper – often called a “Gyproc sheet” (according to the name of the trademark).
Laboratory tests have shown that replacing gypsum with unheated earth between the paper layers of a panel is feasible in existing plants and that costs and performance appear acceptable. A pilot project in a construction site is planned.
According to Mr. Blanchet’s preliminary assessments, replacing gypsum panels with earth panels would save 200,000 tonnes of waste per year, since the latter are more easily recyclable.
Raw earth
The idea came about two years ago during an informal discussion with people in the construction industry. “I hold a chair on sustainable buildings,” says Mr. Blanchet. We take into account the comfort of the occupant and the end of life of the materials. In construction, we consume 40% of the materials used by humans on the planet. I heard about gypsum panels at this meeting and thought I would look into the subject. »
The Quebec researcher had heard of uses of “raw earth” in Belgium to make bricks. The raw earth is not heated, which reduces the energy required to manufacture the material. Please note: the bricks used in Quebec are heated.
The next step, in addition to the pilot project, is the evaluation of the “life cycle” of the raw earth wall panels, to see if their durability is good, and therefore if their cost is comparable. “A priori, we could manufacture them in the same factories as gypsum panels,” says Mr. Blanchet.
PHOTO PASCAL RATTHÉ, SPECIAL COLLABORATION
The soil used in the composition of the panels is clayey soil from the Laval University campus.
He also wants to test the proportion of wood fibers to be integrated into the raw earth so that the performance reaches a level comparable to that of gypsum panels. Life cycle analysis will also make it possible to calculate the energy saved. The proportion of wood fiber would not exceed 4%, which would not constitute a problem with regard to fire standards.
The raw earth panels should block sound more than gypsum, which would give an advantage to this ecological solution, according to Pierre Blanchet.
Will the presence of organic matter, and therefore bacteria in the soil, pose a problem? “You need the least amount of organic matter, particularly because it reduces fire resistance,” he answers. We do not take the top soil [humus]. »
According to figures from the Bureau of Mines and the Gypsum Association of the United States, the gypsum panels in a new American home generated one to two tons of CO equivalents2 in greenhouse gases (GHG), which is equivalent to the average amount of GHG emitted by a car in two to four years in the United States.
The little history of gypsum panels
Gypsum has been exploited since ancient Egypt. It was used in the form of plaster in dry environments to cover walls. European Renaissance frescoes were mostly made with lime plaster, because gypsum does not tolerate humidity well. This is why special gypsum panels, with additional protection, are needed for bathrooms.
At the end of the 18th centurye century, French chemist Antoine Lavoisier identified the chemical composition of gypsum, which led to the commercialization of “plaster of Paris.”
Gypsum panels were invented at the end of the 19th centurye century in New York, to replace the handling of plaster with which the walls were coated with wooden slats. Initially, the gypsum sheets, nicknamed “Sackett panels” after their inventor, measured 3 ft. x 3 ft. It was not until the 1960s that the current size, 4 ft x 8 ft, became established.
Learn more
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- 25 billion
- Quantity of 4×8 gypsum panels sold in the United States in 2025, in square feet
Source: Gypsum Association
- 15 billion
- Quantity of 4×8 gypsum boards sold in the United States in 1970, in square feet
Source: Gypsum Association
