Biochar Created from Agricultural Waste Adsorbs Wastewater Contaminants

Biochar is a charcoal-like substance that primarily comes from agricultural waste. It is a promising material for adsorbing and removing wastewater contaminants, especially if derived from cotton gin waste and guayule bagasse.

Useful decontaminating material

Treated wastewater can harbor many known and emerging contaminants, such as those pharmaceutical wastes.

A research team has conducted a new study that compared and evaluated biochar's ability to adsorbing three common compounds from pharmaceutical wastes in aqueous solutions.

This biochar is derived from two leftover common agricultural wastes, namely guayule bagasse and cotton gin waste.

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Adsorption versus absorption

Adsorption involves a material, such as a compound derived from a pharmaceutical, sticking to another compound's surface, such as a solid particle of biochar.

In contrast, absorption involves a material being internally taken into another material, such as a sponge, which absorbs a liquid.

Guayule bagasse

Guayule is a shrub found in the Southwest arid region. It is also known as Parthenium argentatum, which is cultivated for producing latex and rubber. It is chopped, and its branches are mashed for latex extraction.

Its fibrous, pulpy, and dry residue remains when the stalks have been crushed during latex extraction, and this is what is known as bagasse.

Penn State University College of Agricultural Sciences Department of Agricultural & Biological Engineering professor and researcher Herschel Elliott says that it is important to determine biochar's potential. If effective, it is a low-cost component for removing wastewater contaminants in wastewater treated for irrigating crops.

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Removing toxic compounds

Many sewage wastewater treatment facilities cannot presently eliminate emerging contaminants like pharmaceutical wastes. According to Elliott, if biochar can remove these compounds, wastewater may be recycled for crop irrigation. This will benefit the US Southwest and other regions whose crop production activities are hampered by water scarcity.

Tested compounds

The study used pharmaceutical waste compounds for biochar to adsorb. These are sulfapyridine, an antibacterial compound used commonly as a veterinary drug; docusate, which is used in stool softeners and laxatives; and the antibacterial erythromycin, used for treating acne and other infections.

The study authors published their results in the journal Biochar, which suggests that biochars from agriculture wastes are effective adsorbents for pharmaceuticals present in wastewater.

The study found that cotton gin waste-derived biochar has higher efficiency. It adsorbed 98 percent docusate, 74 percent erythromycin, and 70 percent sulfapyridine. Meanwhile, guayule bagasse-derived biochar adsorbed 50 percent docusate and erythromycin while only adsorbing 5 percent sulfapyridine.

The study also found that increased temperature from 650 to 1,300º F in converting the waste to biochar enhanced the biochar's adsorbing capacity.

According to study lead researcher and Penn State doctoral student Marlene Ndoun, guayule bagasse has not been previously tested in past studies. It is also a novelty for the study to use cotton gin waste in specifically removing pharmaceutical waste.

Noun wants their research to have actual practical application in the real world. She thinks cotton gin waste can be very promising because it is readily available in even the poorest areas, and biochar from this agricultural waste, she says, has real potential in removing wastewater contaminants, along with guayule bagasse.

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