October 5, 2023 | by Sarah Hill

Putting Animal Waste to Work

By Sarah Hill

Scientists of the medieval times were searching for a way to turn lead or other substances into gold or silver through alchemy—turning a material of low value into one of higher value. Today’s agricultural and biological engineers have found a way to turn organic biomass into a valuable raw material that has the flexibility to be used in a variety of scenarios.

A North Carolina State University (NCSU) professor is seeking to take waste materials and turn them into products with economic value.

“We can take these unwanted materials and turn them into something useful,” says Praveen Kolar, Professor, Agricultural Waste Management, NCSU.

Synthesizing Biochar

Biocharcoal is made after any type of organic biomass is carbonized, even from waste biomass. Biochar has very specific physical and chemical properties that can be used for different applications, and a unique substance for economic purposes. The production process is simple, according to Rafsan Nur-Al-Sarah, Graduate Research Associate, NCSU, but the essential factors are high temperature and an absence of oxygen. Biochar typically has a large surface area.

“The chemistry is fascinating,” says Kolar. “The surface is composed of certain chemical functional groups that we think are very important in certain chemical reactions.”

The quality and form of the precursor material plays an important role in the chemical composition of the resulting biochar, Kolar says.

Kolar and Nur-Al-Sarah have successfully used poultry litter for creating biochar. In this case, the manure in the poultry litter brings nitrogen, sulfur, phosphorus, and other elements, so when the poultry litter is synthesized into biochar, it creates a unique chemistry.

Fueling Supercapacitors

The pair have researched how biochar baked from poultry litter can be used in supercapacitor applications. Poultry litter is a preferred raw material for producing biochar because it is more dry than other types of animal waste and requires less heat to be formed into biochar.

A capacitor is like a battery, in that it can provide a large amount of energy for a short period of time. A supercapacitor is a much smaller, denser, and more durable capacitor which has the capacity for a lot of energy—several hundred times more than a regular capacitor and can recharge very quickly.

“In those few seconds, a supercapacitor can do a lot of things,” Kolar says. “It can run for several hundreds of thousands of cycles, so that’s the advantage of a supercapacitor.

When biochar is used to power a supercapacitor, it has the chemical capability to store energy in its ions. In fact, the biochar made from poultry litter proved to be faster at storing and distributing energy than biochar made from other traditional energy systems, according to Nur-Al-Sarah.

Typically, the industry uses activated carbon as the fuel for supercapacitors. However, recent research has shown that whenever certain non-carbon items embedded in the carbon matrix, the biocarbon electrode in the supercapacitor becomes more effective—specifically, nitrogen, sulfur, and phosphorus—the very nutrients poultry litter has in abundance.

“The unique chemical features of this type of biochar help us to obtain that objective,” Nur-Al-Sarah says. Kolar agrees.

“We’re getting a natural material that has all the right elements needed for an ideal supercapacitor,” Kolar says. “Compared to pure biochar, the biochar made from poultry litter has proved superior for its charge holding capacity.”

The large surface area of the biochar means more space to attract electrons, which allows the supercapacitor to conduct more energy.

Kolar and Nur-Al-Sarah plan to continue studying poultry litter and its uses as biochar for the next few years, so more will be coming on this exciting research.