Webinar Q&A: CWP Biochar

The Center for Watershed Protection (CWP) is working to accelerate the use of biochar in stormwater management. In an October Stormwater Solutions webinar, speakers discussed CWP’s role in the National Fish and Wildlife Foundation funded project, Scaling Up Biochar in the Chesapeake Bay. The project supported pilot projects demonstrating biochar’s effectiveness in reducing runoff and pollutants. In collaboration with the U.S. Biochar Initiative (USBI), CWP is also developing a practical stormwater biochar guidebook to help practitioners, municipalities, and decision-makers understand best practices for biochar use in stormwater best management practices. Below, the webinar speakers answer common audience questions.

To watch the webinar on-demand, click here.

Audience: Where and by whom is this biochar being manufactured? Is it readily available for use?

Speakers: Biochar is being manufactured all over the US. It is a quickly developing field and can be difficult to determine which biochar producers have quality biochar. Getting the biochar tested would be the first step. USBI hopes to eventually have a list of biochar producers and their test results available on their website.

Audience: How long would biochar be able to retain pollutants until it needs replaced or more biochar added? Has it been found what types of biochar are targeting specific pollutants?

Speakers: There is evidence that biochar is regenerative, and that as it weathers, more attachment sites and pores become available. Some studies have tested for pollutant breakthrough in biochar columns, but this doesn't allow for the weathering to occur, and results are variable. Impact of residence time depends on targeted pollutants. Metals generally adsorb relatively quickly; nutrients less quickly. Biochar's ability to hold water in pore space allows pollutant removal mechanisms to occur in addition to adsorption, including microbial breakdown.

Audience: I'm interested in knowing more about the construction/implementation details of the projects you've completed. Is that information available online, or can it be made available?

Speakers: Please see the projects page at ScalingUpBiochar.com. These may not include specific construction or implementation details for all projects currently, but updates will be made through 2026.

Audience: It seems the BMP goal is crucial for the materials used for creating the biochar. Green BMPs are becoming more attractive for their inter-disciplinary benefits and ecosystem services. That being said, in your experiences is there a biochar material that is the most versatile and beneficial for many design goals?

Speakers: A coarse, wood-based biochar is probably the current front runner in terms of stormwater BMPs. Nutrients and metals tend to be low, which helps with meeting water quality goals.

Audience: A test report was shown in the beginning of the presentation. How do you know if the results are what you are looking for? We will know what problem we have, but how do we know from the test report that the material meets the need?

Speakers: The International Biochar Initiative (IBI) standard includes ranges of various parameters, which the biochar should meet. The Biochar in Stormwater BMP Guidebook will also include some parameters.

Audience: For persistent pollutants, will the biochar eventually release them, or does it permanently bond?

Speakers: Bond strength will depend on the compound bound and other compounds competing for the site. If the bond is strong, the compound can be expected to remain adsorbed for the lifespan of the biochar, which can be anywhere from 100 to 1,000+ years.