Grantee Research Project Results
Final Report: Biochar Wattle for Enhanced Surface Water Quality
EPA Grant Number: SU840146Title: Biochar Wattle for Enhanced Surface Water Quality
Investigators: Hutchins, David , Zodrow, Katherine , LaDouceur, Richard , Pal, Robert , Prieto, Dario
Institution: Montana Technological University
EPA Project Officer: Page, Angela
Phase: I
Project Period: December 1, 2020 through November 30, 2021
Project Amount: $24,946
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2020) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
Stormwater pollution is a growing concern among rural and urban communities. The objective of this project involved 1) producing a biochar adsorbent with local waste materials and 2) incorporating the biochar into an innovative technology for mitigation of surface runoff pollution. Biochar is a high surface area and porous material that proves useful for soil and water remediation. This project seeks to address surface runoff of metals, sediment, and other contaminants by implementing a composite biochar wattle design.
This project has optimized and assessed the effectiveness of a novel stormwater treatment technology. The project aimed to innovate an affordable and simple solution for surface water pollution challenges. This technology was demonstrated in the disadvantaged community of Uptown Butte, MT, which lies in the nation’s largest Superfund site. The residents in Butte and the surrounding aquatic ecosystems suffer from heightened exposure to metals from historic mine waste. Potential benefits to the environment include reductions in erosion and contaminants in runoff, thereby reducing human exposure and threats to aquatic life. The wattle design employs environmentally benign, locally sourced waste materials and low-cost fabrication techniques, thus ensuring sustainability and accessibility. The unique composite toroid construction of the wattle represents a significant innovation in stormwater management.
Summary/Accomplishments (Outputs/Outcomes):
The first objective focused on identifying potential sources of biochar, optimizing the production of biochar, and characterizing the finished product. The team identified Hemp stalks, Ponderosa Pine timber waste, and bovine osseous matter, or cow bones, as the potential feed stocks. Thermogravimetric analysis facilitated the optimization of pyrolysis conditions, which was standardized at 700˚C for 5 hours in a furnace flooded with argon gas. The resulting chars were characterized via SEM imaging, N2 physisorption measurements of surface area, and adsorption experiments. Isothermal adsorption experiments were conducted at equilibrium with single and mixed metal solutions and used to determine relevant parameters. It was found that although the bonechar did not present with the greatest surface area, it did have the greatest adsorption capacity.
Figure 1 Bench-scale metal removal with bone and pine char
blend and mixed metal solution
The second objective was to incorporate the biochar into an innovative technology for mitigation of surface runoff pollution. Experiments began with a purpose-built bench-scale apparatus. The apparatus was designed to mimic the passive flow adsorbents in a wattle would experience, with the flexibility to test various flow rates, volumes, types, and blends of chars. Bench-scale experiments included pine and bone chars with copper and mixed metal solutions. In the case of the copper solution, influent and effluent metal concentrations were analyzed with a photo spectrometer. For the mixed metal solution ICP-OES was used to detect multiple analytes in solution. Initial experiments showed suboptimal performance from either pinechar or bonechar. Slow adsorption kinetics with the pinechar and excessive pH affects with the bonechar, and subsequent precipitation, resulted in unacceptable removal efficiencies. After multiple iterations, a blend of 10% pinechar and 90% bonechar was found to be effective. As can be seen in figure 1, the final bench-scale experiments were successful in achieving the benchmark of 96% copper removal, and in addition was able to remove greater than 90% of the total metals in the mixed metal solution.
Following experiments with the bench-scale passive flow apparatus, work began on a fabricated wattle. The data gleaned from
the first Objective and the apparatus were incorporated into an experimental plan designed to test the efficiencies of a toroidal adsorbent wattle. Variables included casing materials, initial copper concentration, and size fraction of the adsorbent media. Early results showed a clear advantage with a tight-weave cotton casing material. The smaller fraction of biochar media grain size (1-2mm) showed a clear advantage, however, the larger fraction (5-12mm) had acceptable removal efficiencies (92%). At the given flow rates, the wattle was not effective at reducing copper from a high concentration solution (200 mg/L) but was effective at lower
concentrations (8 mg/L). Removal efficiencies with the lower concentration were found to average 98% over multiple cycles. The lower initial concentration of 8 mg/L is representative of mine affected waters and is excessive for urban stormwater. Based on all previous findings, a pilot-scale composite wattle was designed and fabricated, as shown in figure 2.
The third objective was to assess the effectiveness of the biochar wattle. While initial results suggest success in this
objective, the work continues and is inconclusive. It is anticipated that the milestones in this objective will be accomplished in the coming months. Experimental plans include implementation of the toroidal wattle in the urban setting and implementation of the sock at an abandoned mine. The team has worked with the EPA and local municipality to access a suitable storm drain, and the Big Hole Watershed committee to access an abandoned mine site they manage. The team has full confidence that all objectives will be met by project end in October 2021.
Figure 2 Pilot-scale biochar and straw composite wattle
Conclusions:
In conclusion, the research team has successfully produced biochar adsorbents with locally sourced and sustainable waste materials, and incorporated the biochar into an innovative technology for mitigation of surface runoff pollution. The team is utilizing ponderosa pine and cow bone feedstocks to produce highly adsorptive biochars capable of reducing copper and other metal concentrations by 98% or more. The biochars have been incorporated into toroidal composite wattles that are designed to be deployed at urban storm drains and socks that are designed to be deployed in mine affected waters.
This project has the potential to result in quantifiable benefits to people, prosperity, and the planet. Reduction of metal concentrations in urban surface waters will reduce human exposure and protect aquatic life. In the primary research site of Butte, Montana, exceedances of the surface water standards for copper and zinc are a regular occurrences and fish kills have been observed. The technology developed and data gathered in this project suggest implementation would result in a reduction in metal loads to below compliance with applicable standards. The technology holds much promise for prosperity, as well. All of the materials are sustainable and locally produced and, if implemented, would result in entrepreneurial and employment opportunities.
In addition, the project presents many qualitative benefits to people, prosperity, and the planet. The educational and public outreach components of this project were strong, reaching multiple middle school and high school STEM classrooms and hundreds of citizens in the community. A curriculum was developed for teaching the public about stormwater pollution, the EPA, and P3. The project was a major component of the student team’s education, serving as their senior capstone project. Three of the students have received their degrees in the course of the project and the remaining students will graduate in the coming semester. Future work will include the remaining components of Objectives B and C. The wattles will be evaluated on-site and their performance quantified.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
Biochar, Stormwater, Adsorption, Wattle, Metal Contaminants, Environmental Engineering, Water treatment, sustainableThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.