Biochar from agricultural waste products shows promise of removing contaminants from pharmaceutical products

Reviewed by Emily Henderson, B.Sc.November 17, 2020

Biochar, a coal-like substance made primarily from agricultural waste products, promises to remove emerging contaminants such as drugs from treated wastewater.

This is the conclusion of a team of researchers who conducted a new study that evaluated and compared the ability of biochar derived from two common advanced agricultural materials – cotton gin waste and guayule bagasse – to adsorb three common pharmaceutical compounds from a water solution.

In adsorption, one material, such as a pharmaceutical compound, attaches itself to the surface of another, such as the solid particle of biochar. Conversely, during absorption, one material is brought internally into another; for example, a sponge absorbs water.

Guayule, a shrub that grows in the arid Southwest, provided the waste for one of the biochars tested in the research. More properly called Parthenium argentatum, it has been cultivated as a source of rubber and latex.

The plant is cut to the ground and its branches are crushed to extract the latex. The dry, pulpy, fibrous residue that remains after the stems have been squeezed to extract the latex is called bagasse.

The findings are important, according to researcher Herschel Elliott, a professor of agricultural and biological engineering at Penn State, College of Agricultural Sciences, because they demonstrate the potential for biochar produced from abundant agricultural waste – which otherwise must be disposed of – to serve as a treatment. low cost additive to reduce contaminants in treated wastewater used for irrigation.

“Most wastewater treatment plants are currently not equipped to remove emerging contaminants such as drugs, and if these toxic compounds can be removed from biochars, the wastewater can be recycled into irrigation systems,” he said. “This beneficial reuse is key in regions such as the Southwestern United States, where lack of water hinders crop production.”

The pharmaceutical compounds used in the study to verify whether the biochars would adsorb them from the aqueous solution were: sulfapyridine, an antibacterial drug no longer prescribed for the treatment of infections in humans but commonly used in veterinary medicine; docusate, widely used in medicine as a laxative and stool softener; and erythromycin, an antibiotic used to treat infections and acne.

The results, published today (November 16) in Biochar, suggest that biochars made from agricultural waste materials could act as effective adsorbents to remove drugs from wastewater prior to irrigation. However, biochar derived from cotton gin waste was much more efficient.

In the research, it adsorbed 98% of docusate, 74% of erythromycin and 70% of sulfapyridine in aqueous solution. In comparison, guayule bagasse-derived biochar adsorbed 50% of the docusate, 50% of the erythromycin and only 5% of the sulfapyridine.

The research revealed that an increase in temperature, from about 650 to about 1,300 degrees F in the oxygen-free pyrolysis process used to convert agricultural waste materials into biochar, led to a greatly improved ability to adsorb pharmaceutical compounds.

The most innovative part of the research was the use of guayule bagasse because there have been no previous studies on the use of that material to produce biochar for the removal of emerging contaminants. “

Marlene Ndoun, lead researcher and PhD student, Department of Agricultural and Biological Engineering, Penn State

“The same goes for cotton gin waste: research has been conducted on potential ways to remove other contaminants, but this is the first study to use cotton gin waste specifically to remove drugs from water.”

For Ndoun, research is more than theoretical. He said he wants to increase technology and make a difference in the world. Since cotton gin waste is widely available, even in the poorest regions, he believes they hold promise as a source of biochar to decontaminate water.

“I am originally from Cameroon and the reason I am here is also because I am looking for ways to filter water in communities with limited resources, such as where I grew up,” she said. “We think if this could be magnified, it would be ideal for use in sub-Saharan African countries where people don’t have access to sophisticated equipment to purify their water.”

The next step, Ndoun explained, would be to develop a blend of biochar material that can absorb a wide range of contaminants from the water.

“In addition to removing emerging contaminants such as pharmaceuticals, I am interested in blending biochar materials in order to have low-cost filters that can remove the typical contaminants we find in water, such as bacteria and organic matter,” he said. said Ndoun.