Mast Reforestation sells out first biomass burial carbon credits in six weeks, targets 150,000 tonnes a year

Seattle-based Mast Reforestation sold 100% of the 4,277 carbon removal credits from its first biomass burial project - Mast Wood Preserve MT1 in southern Montana - within six weeks of their January 2026 issuance on the Puro.earth registry^[1]. The sell-out, confirmed in April 2026, validated a financing model that uses carbon credit revenue to pay for the most expensive step in post-wildfire recovery: clearing dead trees and replanting the land^[1].

What the vault does

Mast buried more than 10 million pounds of fire-killed trees in a clay-lined, oxygen-free underground chamber at the MT1 site in Bighorn County, Montana, on land burned severely in the July 2021 Poverty Flats Fire^[1]. The project yielded more than 4,500 metric tons of biomass sealed in a clay-lined vault, capped with a geoengineered textile, gravel, and organic matter, with native grasses planted on top. Sensors inside the vault monitor temperature and humidity for signs of decomposition, while above-ground sensors continuously track carbon dioxide and methane levels.

Biomass burial - formally Terrestrial Storage of Biomass (TSB) - is considered one of the most efficient biomass-based carbon dioxide removal pathways; Mast claims the process sequesters twice as much carbon as biochar production from the same feedstock. The method is protected under a 100-year easement, with research suggesting preservation could last up to 3,000 years.

The financial arbitrage

The mechanism works because removal credits command a premium in voluntary carbon markets. Such removal credits fetch a higher price, even after steep volume discounts for corporate buyers. MT1's January 2026 issuance was the largest to date under Puro.earth's TSB methodology and one of the fastest project development timelines globally for a carbon removal project - nine months from excavation to issuance.

Buyers at sell-out included:

• Royal Bank of Canada
• Bain & Company
• BMO
• CNaught (whose customers include HMC Architects, Rocky Talkie, and Workato)
• Muir AI^[1]

Proceeds from credit sales are directly funding post-wildfire reforestation in Bighorn County, an area that burned so severely during the 2021 fire that natural recovery was unlikely within the next century or more. Mast is planting more than 6,000 native conifer seedlings grown from wild-collected, locally adapted seed at its Silvaseed nursery in Roy, Washington.

The scale problem it is trying to solve

The U.S. Forest Service estimates that 80% of reforestation needs on national forest lands are due to wildfire, with cumulative post-wildfire reforestation needs in the western U.S. reaching around two million hectares as of 2021. Intense burns wipe out seeds and trees' ability to regenerate; 43% of studied California burn zones had no new trees five years after a fire. Mast estimates there are 2.3 million tonnes of dead, burned trees across Montana alone from wildfires in the last four years. The company has since revised that figure upward: Mast now identifies more than 6.5 million tonnes of burned biomass in Montana alone as eligible for burial projects^[1].

Mast pivoted to biomass burial after announcing $25 million in Series B financing in February 2025, co-led by Chamath Palihapitiya's Social Capital and Los Angeles-based climate VC Pulse Fund.

What to watch

Mast's next target is projects containing about 20,000 metric tons of biomass each, with a pipeline goal of 150,000 tonnes buried per year. The credibility test will be whether that volume can be verified and sold at the same pace as MT1 - and whether corporate buyers sustain demand as the voluntary carbon market continues its recovery from a period of fraud and miscalculation that depressed credit prices after 2021. The Trump administration's cuts to Forest Service staffing and reforestation budgets add urgency: private carbon finance may be the only mechanism with the speed and scale to clear burned landscapes before they fuel the next fire^[1].