Did you know that waste from the olive oil industry such as olive stone ash, ground olive stones, and sludge from pomace oil extraction can be used as effective secondary raw materials in the creation of clay bricks and cement paste?
The extraction of pomace oil and the process of oil refining generate waste water in the form of sludge. This at times is used as a fertilizer in agriculture but most often it’s dumped in landfills or water bodies, or incinerated — creating a negative environmental impact.
A 2015 study titled Reusing of Oil Industry Waste as Secondary Material in Clay Bricks by the Department of Chemical, Environmental, and Materials Engineering at the University of Jaén, Spain, found that the use of sludge leftover from pomace oil extraction in the making of clay bricks had a comparable compressive strength as conventional bricks, but they had better thermal conductivity.Furthermore, the study also revealed that industrial oil waste products such as sludge, as well as spent filtration and bleaching earth (both are used for refining oils) can also be used expertly as substitutes to brick clay due to the fact that their chemical composition closely resembles it.
The same research team released an article a year later in 2016 that evaluated the use of olive stone ash as a secondary raw material for fired clay bricks. In that time of research, they discovered that adding 10 to 30 wt% (weight percent) of olive stone ash to clay had a “pronounced effect on the evolution of physical and mechanical properties of the resultant bricks fired at 900°C.”
Nonetheless, adding higher proportions “decreased the compressive strength and bulk density of bricks” while increasing their porosity and rate of water absorption.
Another 2016 study looked at the effects of the addition of ground olive stones on the physical and mechanical properties of clay bricks.
In that 2016 study, they analyzed the properties of bricks made with clay and ground olive stones and discovered that the addition of the latter reduced water absorption which can have a positive effect because it decreases the chance of crumbling while creating an exceptional bonding effect.
The 2016 study concluded that clay bricks manufactured with ground olive stones “offer outstanding returns on the energy used in firing”, and “are suggested as one of the most cost-effective alternative additions that can be used in fired clay brick manufacturing.”
The reuse of these olive waste products as alternative raw materials in the construction industry not only reduces industrial waste but can also offset the cost of raw materials. At the same time, this is an eco-friendly and sustainable way of recycling waste that also saves natural resources.