Making use of wasted products
1
Many people see biochar as a waste product, but Professor Krishna Reddy sees it as a wasted product.
Biochar is the leftover solid byproduct created when biomass such as wood, peanut shells, cornstalks, and other organic materials are thermally treated in a low-oxygen environment, a process called pyrolysis.
“People who are processing biomass for biofuel consider this a waste material,” said Reddy, director of the Geotechnical and Geoenvironmental Engineering Laboratory at UIC. “As more research is conducted on the material, investigators have found it has very unique characteristics and can be used for other purposes.”
When burned using low oxygen, biomass forms a very nice structure with many micropores, making it well suited for microbes to reside, acclimate, grow, and be active and absorb contaminants.
“Some of these biochars also have chemical groups on the surface so they can bond with contaminants, and they have a lot of applications in the environmental field. I have been using it in landfill covers, and I’m the first to use it for such an application,” he said.
Microbes are not very active in soil alone, and by adding biochar to the landfill soil, Reddy observed that it helped capture greenhouse gases that were coming up and reduced the release of these global-warming gases.
In addition to capturing gases, biochar can be used as a filter material to remove contaminants from stormwater, wastewater, and groundwater. Biochar has a high surface area and high microporosity, which helps remove contaminants as water moves through it.
“We looked at it for applications like stormwater treatment in bioswales. Generally, the water is allowed to infiltrate, and if the water is clean, you don’t have to worry. But if the water is not clean, you want to put some filter material at the bottom. Biochar is a low-cost filter material, and the advantage of this biochar is that you can use any biomass to produce it,” Reddy said.
Reddy is quick to point out that not all biochar is the same. Biomass comes in many forms, such as agricultural waste, garbage, sewage, or animal litter. His research found that manure – from pigs, chickens, and cows – is used to make biochar in China.
“You could be using a different biomass, and you get a completely different biochar,” he said. “You could be using the same feedstock, but using a different way of treatment can lead to a different type of material.”
When creating biochar, people need to consider several factors. Varying temperatures and how much biomass is heated can produce biochar with different properties.
“I looked at the combinations, and the different ones are overwhelming. I estimated about 16,000,000 possibilities of biochar types, critically looking at all the combinations and permutations,” he said.
With all these combinations, Reddy encourages people to be careful about the initial characterization of the material. Creating a biochar with undesirable contaminants that could leach out while trying to filter something out would be counterproductive.
“If the biochar you produce is not working out for your purpose, you can engineer it and modify it in different ways. Don’t give up because you can do the physical treatment, you can do the chemical treatment, you can do the biological treatment, you can do the magnetic treatment. There are many ways to engineer it to suit the purpose,” Reddy said.
In addition to environmental engineering, there is a need for innovative or engineered materials to solve many engineering functions. Biochar is used in concrete and construction materials, and some biochar is used for electrodes and other electrical applications.
“Instead of sending the waste to landfills, it can be a valuable resource. The so-called waste product is no longer a waste product. It’s a product that is being wasted without knowing the value of it,” he said.