Press
Biomass Magazine: How Two Submariners Built a Rice-Hull Biochar Plant in Arkansas
- rice hull biochar
- Stuttgart Arkansas biochar
- pyrolysis rotary drum
- organic Rankine cycle biochar
TL;DR
Biomass Magazine has published a feature on Cold Steppe's Stuttgart, Arkansas facility, written by Katie Schroeder. It traces the project from incorporation in September 2024 to a commissioned plant in December 2025, and covers the equipment choices, the feedstock, and the agronomy behind selling biochar to farmers rather than to a carbon market. This is a short summary. Read the full article at Biomass Magazine.
What the article covers
Katie Schroeder's piece follows co-founders Kevin Crow and Matt Freniere from a friendship formed in college, through service together on a nuclear submarine, to two separate careers that happened to converge on the same material. Crow had worked at a Tennessee company using biochar for water filtration; Freniere was at a data center business spinning out a biochar venture. The subject kept coming up on their catch-up calls.
The timeline is the part most people ask about:
| Milestone | When |
|---|---|
| Cold Steppe incorporated | September 2024 |
| $15 million financing closed | June 2025 |
| Groundbreaking | July 2025 |
| Construction and commissioning complete | December 2025 |
Two of the four kilns are running today. The third and fourth are due by the end of 2026, taking the facility from roughly 20,000 tons of feedstock a year to 40,000 - about 20,000 tons of biochar from rice hulls grown nearby.
Why rice hulls, and why Arkansas
Arkansas has led US rice production for fifty years, which puts a very large, very local pile of rice hulls within reach of a plant in Stuttgart. Hulls are also awkward: their silica content is abrasive on material-handling equipment, and they bind rather than pile, so they behave differently from a granular feedstock in conveyors and hoppers.
The article describes how the team worked around that - custom parts, and sending feedstock samples to equipment manufacturers during engineering rather than discovering the problem at commissioning. Freniere's view, quoted in the piece, is that the same silica that makes the material difficult to handle is worth having in the finished product for agricultural soils.
The reactor habit
The framing that gives the article its title is the submarine one. A pyrolysis kiln and a nuclear reactor both run a self-sustaining reaction that continues as long as the energy balance holds. Freniere describes applying "nuclear power-style engineering" to the plant - designing for consistency batch to batch, choosing components that are straightforward to repair, and keeping the process simple enough that a new operator can learn it.
Two supplier decisions get detailed treatment:
- BioMass Energy Techniques' Pyrolysis Rotary Drum (PRD3000), which processes 3,000 pounds of feedstock an hour and runs continuously rather than in batches. Four of them at full capacity.
- ElectraTherm organic Rankine cycle generators, which turn waste heat into electricity. The article explains why that flexibility matters with a biomass fuel, where moisture and BTU content vary from batch to batch and the leftover heat varies with them.
The agronomy, briefly
The reason the article spends time on soil is that Cold Steppe picked the end use first and designed backwards from it. Biochar built for a soil amendment is not the same specification as biochar built for cement or for a voluntary carbon market.
The mechanism described is the familiar one: adding stable carbon back to soil that has been farmed for decades raises cation exchange capacity, which improves how well the soil holds on to fertilizer and water. Research and field data indicate this matters most in southeastern soils, where temperature and soil biology make organic matter hard to build up by other means.
Read it in full
The full feature includes more on the local support the project drew in Stuttgart, the engineering partners, and where the founders expect the biochar market to go next.
A Big Steppe - Biomass Magazine, 6 July 2026, by Katie Schroeder
FAQ
Where is Cold Steppe's facility?
Stuttgart, Arkansas, in the middle of the state's rice-growing region and close to the mills that produce its feedstock.
What does the plant make it from?
Rice hulls - a byproduct of rice milling, sourced from nearby farms and mills.
How much biochar does it produce?
Around 10,000 tons a year at present, from 20,000 tons of feedstock. With the third and fourth kilns online by the end of 2026, the target is 20,000 tons of biochar from 40,000 tons of hulls.
Who wrote the article?
Katie Schroeder, for Biomass Magazine, published 6 July 2026.