Witnesses urge Vermont to endorse local 'rock dust' black shale to capture phosphorus and support farmers
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Summary
Witnesses and industry representatives told a legislative committee that locally sourced black shale rock dust can capture soluble phosphorus, improve soil health, and serve as a fertilizer filler; they asked the state to endorse the material for best-management practices and consider funding or credit mechanisms to create a market.
Tom Vanapar, who identified himself as a witness from Bridgeport, told a legislative committee that local quarry byproducts—particularly carbonaceous marine "black shale"—can be broadcast on fields to capture soluble phosphorus and improve soil health. "We could actually, capture phosphorus running to the ditches, retain it on the surface of the product," Vanapar said, describing field trials run with University of Vermont extension staff and a university professor. He said the trial material was produced at local quarries and that soil sampling before and after application showed a meaningful reduction in phosphorus transport over one winter season.
Vanapar said his team entered the Vermont Phosphorus Innovation Challenge and reached later rounds of the competition, but that state reviewers did not endorse commercialization. "We weren't asking for money," he said. "We were looking for the state would endorse the materials and methods for best management practices." He told the committee a 150-page report documents the work and that third-party academic testing supports the results.
A representative from Sheldon Limestone (speaker did not give a name on record) described continuing industrial testing and commercial interest. The representative said the quarry in Swanton contains a large estimated resource and that processed fines could be pelletized or used as fillers in bagged fertilizer products. "We estimate maybe about 30,000,000 tons of this product that could be processed into a pelletized product," the speaker said, adding that the material reacts in the soil and could replace calcium carbonate or biosolid fillers.
Speakers described how the material would fit into existing conservation programs if the state were to endorse its use. Vanapar cited federal and state programs and conservation practice codes (recorded in the transcript as "3 36", "5 90" and "7 82") and urged that the Agency and committee consider adding rock-dust applications to accepted best-management practices or Pay-for-Phosphorus mechanisms. He framed the request as a market-creation problem: producers face up-front processing investments while farmers will not buy the product at scale without programmatic recognition or financial incentives.
Committee members asked about agronomic function and composition. Vanapar said rock powders supply macro- and micronutrients and foster microbial activity; they do not generally replace nitrogen fertilizers but can improve nutrient delivery and make existing fertilizer more available to crops. Industry participants noted barriers—including abrasion during processing that raises costs—and suggested state help to create demand for processing fines and other byproducts.
The committee chair thanked the panel, said staff (including Sarah Heffernan) would follow up, and invited the witnesses to remain available for additional conversations. The group left the committee with a request for administrative endorsement, clarity about which conservation codes apply, and discussion of potential credit or funding mechanisms to help scale production and application.
