A New Stormwater Filter Media featuring (wait for it…) Biochar

By Pat Sherren (Director, New Product Development & Sales, Metzler Biochar)

In today’s world, water and pollution go together like, a Big Mac® and fries. You get one, your probably going to have the other.

Regulatory bodies across the country have quality standards for stormwater that leaves a property, both during construction activities (called erosion and sediment control or E&S) and after construction activities (call Post-Construction Stormwater Management or PCSM).

Lots of things can be nasty about the stormwater and a lot of approaches can be used to do something about it – settling, filters, chemical treatments, flocculation, and on and on. It’s kind of complicated.

But plenty of research and industry effort are going into figuring out how to clean stormwater. So we starting thinking…could biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More have a place here?

In mid-2023, a new flexible Stormwater Filter Media was developed for use in both E&S and PCSM applications called Char21 SW™. It’s a blend of various inert materials that include biochar, switchgrass, re-activated carbon and calcium silica sand. The goal is to stuff this blended material into various devices – mesh tubes, bags, pillows, filter cartridges, filter cells, etc., and run stormwater through at smart locations on a property where stormwater collects.

Why multiple materials in the blend? It’s a broad spectrum, pollution affinity approach. Each material acts a little differently; blended together they are powerful. The switchgrass develops better pollution grabbing affinity over time, but the biochar and re-activated carbon have higher affinity early on. The calcium silicate sand increases the pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More (valuable if the water is too acidic) and can precipitate out things like iron. For highly acidic water, add more calcium silicate. For oily water, increase the switchgrass. It’s a flexible, broad-spectrum approach using earth-friendly materials.

A few more practical considerations of Char21 SW™ – its shelf stable after blending, light weight (but heavy enough to stay in place), consistent from blended batch to blended batch, a true “grass-growing” soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity. More at decommissioning, awesome pollution affinity and sediment retention, lasts about a year in the field, is cost effective, and works well with biodegradable netting.

Nice idea, but now we have make it and test it, and this is where things get interesting. A few phone calls and e-mails later, the team was assembled.

Under the watchful eye of Shawn Grushecky at West Virginia University and in collaboration with MASBio (Mid Atlantic Sustainable BiomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More Consortium for Value Added Products), the team (Metzler Biochar, Ruckus Environmental, Harsco Environmental and Wakefield Farms) set out to test the new filter media. Dr. Grushecky and MASBio supported the effort using part of a $10 Million USDA NIFA grant.

The randomized interval pour trial was designed to mimic natural rain events over a moderate amount of time. The test simulated 20 rain events over a 3 month period. The randomized interval between pours was as short as a few hours or up to 10 days. All 20 rain events exposed the filter media to polluted water. Before and after the filter media, water samples were collected and sent to the lab for comparative analysis at pour events 1, 10, and 20.

Char-21 SW^TM showed strong and increasing affinity for the stormwater pollutants

This effort is another example showing that government, academia and industry can do great things when they join forces to tackle 21^st century problems with 21^st century technology.

Char-21 SW^TM products are on the market today. Other blends of Char-21^TM are in the works to address additional environmental concerns, such as nutrients and PFAS.

LEARN MORE

Pat Sherren, Director of New Products at Metzler Forest Products and Metzler Biochar was a procurement forester for 32 years and fell into an opportunity to innovate and develop new forest products for a great company.