Dry stacking, where trunks, branches, tops, leaves, and twigs are captured and stored in a storage chamber, could be an efficient and cost-effective method for achieving carbon dioxide removals (CDR) when higher-value uses of biomass are not feasible. That is according to Dr Fabiano Ximenes, one of the world’s foremost experts on Forest Carbon, who says that the disposal of wood waste can play a significant role in the long-term carbon mix.
“Over the years, we have done a lot of work understanding the carbon dynamics around disposing of wood products in landfills,” Dr Ximenes told Wood Central today. “What we were able to show is that if you put wood products in landfills under anaerobic conditions, they represent a carbon reservoir for the long-term carbon,” he said.
More recently, Dr Ximenes said start-ups like Inter.Earth, which last year received $8.25 million from investors to scale up its proprietary carbon capture solution, demonstrated the tremendous potential for Australian native tree species (including Eucalyptus and Acacia) to be “dry stacked” and stored in sealed above-ground chambers or below ground at he right depth and conditions for their biomass value.
“These species are adapted to dryland conditions and have high biomass (CO2 capture) production rates from low-value land, which positively contributes to our cost-effective CDR,” according to Dr Howard Carr, CEO and Founder of Inter. Earth, who said the start-up is taking cleared and windrowed plantation trees that would be destined for biochar, which in turn, provides a windfall for landowners, as well as saving the planet.
“The selected species’ woody biomass also has a high C: N ratio, high crystalline cellulose and aromatic tannin contents, all of which positively contribute to decomposition recalcitrance,” Dr Carr told Wood Central. “All stored dried biomass is weighed and sampled, and analysed for moisture and Total Organic Carbon (TOC) at the point of deposition into the
Dry Stack, and regularly (every 30 days) after Dry Stack closure. Biomass captured CO2 is measured (biomass weight x TOC) and not estimated or modelled, allowing for accurate, verifiable and reliable CDR calculations.”
Dr Carr said that Inter. Earth has two sources for its dry stack biomass: One is the 1990s and early 2000s MIS schemes, where vast volumes of Eucalyptus were planted without consideration for the distance to, or the existence of, future tree processing facilities or ports. And the other, Grow-Your-Own Biomass, “where we plant 13 different species of high-production, dryland-adapted, Australian Eucalyptus and Acacia trees on our land. Plantation layout is optimised with accessways for tree husbandry, including Supplementary Watering to increase seedling survival and early growth rates, and subsequent harvest and removal.”
“Grow-your-own biomass is our preferred feedstock source as the vertical integration provides us with end-to-end control of the supply chain and legal ownership of the Dry Stack site,” Dr Carr said. “It does, however, require a relatively large up-front capital expenditure in land purchase, plantation establishment and husbandry, and around 4 years for the first harvest, CDR production and revenues.”
- To learn more about the potential of woody residues for carbon capture, click here for Wood Central’s special feature from earlier this month. And to learn more about Dr Carr’s Inter. Earth, click here to visit the website.
