Using Biochar to Clean Out Pharmaceuticals from Our Precious Streams and Waterways
Carla Ndoun Tangmo is a graduate student at Penn State University. Carla is using ARS-funded research to determine the effectiveness of natural biochar to adsorb pharmaceutical contaminants before it reaches our streams and waterways.
UM: How are pharmaceuticals getting into our streams and waterways?
CT: I have a love/hate relationship with pharmaceuticals. Did you know that when we use pharmaceuticals, our bodies only absorb about 30%, and the remaining 70% is excreted and ends in wastewater? However, the technology in place to clean this wastewater is not equipped to remove pharmaceuticals, leading to the transfer of pharmaceuticals into soils and water bodies. Once in the environment, pharmaceuticals can transform into more harmful products.
Pharmaceuticals are abundant in the environment, especially in wastewater. Once in the environment, these pharmaceuticals can accumulate in the soils and in edible parts of plants. This leads to concerns over potential toxicity to humans, particularly for those food products we consume raw. In addition, pharmaceutical compounds are designed to be bioactive even at low concentrations, and they can cause harm to aquatic organisms including the feminization of fish where fishes show both male and female characteristics.
UM: How does recycling water for irrigation affect agriculture, human health, and the environment?
CT: Reusing wastewater for irrigation or discharging wastewater into water bodies introduces pharmaceuticals into soils, where they can transform into more harmful products and be taken up by food crops. There have been concerns over the potential ecotoxicity for human and animals through the consumption of water and food contaminated with pharmaceutical residues. Continuous accumulation and perseverance of these chemicals in the environment can lead to several ecotoxicological risks such as interference with endocrine systems of higher organisms, intersex characteristics in organism such as fish, and microbiological resistance among bacterial populations.
UM: Can wastewater treatment plants remove pharmaceuticals?
CT: Wastewater treatment plants were not designed for pharmaceutical removal. Also, concerns about the ecotoxicity of pharmaceuticals is fairly recent, so it will take some time for current treatment technology to match the state of science.
UM: What is biochar and how does it fit into the solution for helping to filter our waterways?
CT: Biochar is a substance similar to charcoal, produced from burning waste at elevated temperatures. Once the raw material is harvested, it is placed in a pyrolysis oven (a specialized oven that is maintained in an oxygen limited environment) and heated to the desired temperature for the production of biochar. Following pyrolysis, the biochar is cooled and then ground to reduce the size and have uniform particles. See here for more information on biochar and how it's made.
For bench scale laboratory experiments, cylindrical glass columns are used. In each column, we add 8g of biochar and 8g of sand. A solution containing a known concentration of pharmaceuticals is slowly introduced into the columns for 24 hours and samples are collected at specific time periods. These samples are analyzed for the concentration of pharmaceuticals after filtration and compared to the concentration that was present in the solution to estimate how much pharmaceutical was removed. With this technology we aim to treat wastewater prior to its discharge into the environment or its reuse during irrigation (water recycling).
UM: Cotton gin waste and pulp from the guayule plant can be used for biochar. Why are these good substances for biochar, and are there economic or regional benefits to either?
CT: About 2.7 million metric tons of cotton gin waste are generated annually. Incineration and landfilling are the primary disposal methods for this waste, so we thought, if there are already burning the waste, why don't we burn it to produce a value-added product such as biochar. The guayule plant is principally used to produce rubber, but only about 5% of the plant is used during rubber production. Transforming guayule bagasse into biochar can lead to more sustainable production process and push for the commercialization of rubber from the guayule plant. Currently, we are also using biochar produced from walnut shells. Biochar has also been produced from several different waste streams, such as coconut shells, rice husk, corn cobs, tomatoes, and banana and orange peels.
UM: These materials have to be superheated to make biochar. That seems to be a lot of energy use — is it sustainable?
CT: Incineration and landfilling are already used to dispose of the waste, so the waste will have to be heated regardless. Also, the high energy use is just a tradeoff to having the waste being landfilled.
UM: What is the success rate? After the biochar adsorbs the contaminants, then what?
CT: Depending on the pharmaceuticals we are trying to remove (this varies from pain to antibiotics) we can get up to 95% removal after 24 hours. After adsorption, the biochar can be heated to remove the elements of the adsorbed pharmaceuticals and then used as a soil amendment.
UM: How else can biochar be used to help the environment?
CT: Biochar has been shown to have several benefits including mitigating greenhouse gases, improving soil fertility, and removing contaminants from water. A key feature of biochar is its ease in production using different pyrolysis systems that can be sized for small households all the way to wastewater treatment plants serving large communities. In addition, for resource-limited communities that lack access to proper water treatment technologies, a decentralized biochar-based water treatment system could be ideal.
Biochar treatment technologies have the potential to provide clean water while providing several environmental benefits, including the reduction of bio-waste that need to be landfilled. However, the heterogenous and complex nature of biochar systems may result in unpredictable behavior that can make it difficult to design for large scale systems. In addition, design parameters and operating conditions for biochar-based systems are still lacking. Therefore, future research should focus on developing and validating protocols for biochar production and design of biochar water treatment technologies.
UM: As a grad student working on solving a major issue such as water quality, what do you like best about the research you're conducting?
CT: The coolest part of this project is playing around with different materials and getting my hands dirty, I mean literally! On a serious note, I think finding a way to repurpose bio-waste into biochar can transform the open-ended waste disposal system into a closed loop that provides several benefits. In addition, biochar can serve as a tool to address current and future water, food, and energy problems, especially in resource-limited communities.