Woody Biomass Burial- A Novel Carbon Sequestration Solution

Key Takeaways

• Woody Biomass Burial (WBB) is an emerging carbon sequestration technique which involves storing wood-based biomass in burial chambers to slow its decay
• Companies like InterEarth, Kodama, and Carbon Sequestration Inc. are pioneering the implementation of WBB
• While WBB is still in its early stages, it shows promise as a safe and affordable carbon removal solution

Introduction

Woody Biomass Burial (WBB), also known as Wood Harvest Sequestration or Wood Harvest and Storage (WHS), is an up-and-coming carbon sequestration technique which combines nature and technology-based solutions to capture and store carbon dioxide either above- or underground for a long period of time. Woody biomass refers to biomass sourced from forest residues like branches, sawmill residues, scraps of wood, residues from logging, and other similar wood-based sources.

This technique involves burying the woody biomass underground or storing it above the ground in burial chambers while creating and maintaining conditions that limit its decomposition over time, thus halting the release of the carbon stored in the biomass during its life back into the atmosphere. A burial chamber is an enclosure which is sealed or covered and can be filled with the woody biomass sequentially. There are certain conditions which are essential for building the burial chambers.

First, the chamber should be constructed in such a way that the biomass is kept apart from the atmosphere. The oxygen levels in the chamber should be low and there should be an absence of light. Moreover, there should be a possibility to control the temperature and the moisture levels. The choice of woody biomass is also an important characteristic to be considered as lignin containing biomass naturally resists decomposition.

Current Market Scenario

The only methodology available for WBB has been published by Puro in 2022. This removal method is relatively novel, and there are only few companies which engage in it:

• InterEarth is an Australian startup which grows trees, harvests their above-ground biomass and stores it underground. They have recognised that the native woodland species originally cleared to allow for farming in some farmland areas in Australia are highly efficient at capturing atmospheric CO2, especially when routinely harvested and allowed to regrow. Moreover, they state that by enabling trees to absorb salty groundwater prior to burial, the wood can be effectively preserved for longer durations.
• Kodama is a comprehensive forest restoration team that aims to enhance the effectiveness of forest thinning treatments and streamlining the supply chains for biomass. By using woody biomass acquired from forest thinning for burial, they have identified an optimal solution that entails eliminating landscape risks without contributing greenhouse gases to the atmosphere, while also ensuring low financing costs.
• Carbon Sequestration Inc. has projects based in Texas where forests are actively managed, and a portion of them is selectively harvested by collecting dead wood, timber debris, and other residues. These wood residues are subsequently buried in engineered sub-surface pits under anaerobic conditions to slow down their decomposition.

Advantages

By combining the aspects of nature-based and technology-based solutions, WBB offers the best of both worlds. The risk to the environment is quite low since the worst-case scenario is that the biomass would decay, which would have happened in the absence of the implementation of the project anyway.

There is a high potential to scale this process as well due to the ease of availability of woody biomass. Additionally, this process offers high durability since the carbon can remain sequestered for hundreds of years. WBB is an economically viable removal method since arid land can be put to use for burial chambers. Dense and overgrown forests increase the risk of severe wildfires. The added impact of climate change has intensified these hazards by creating hotter and drier conditions.

By cutting down undergrowth and periodically thinning the forests, the risks of such adverse events can be brought down, and the biomass generated can be used for burial. The cost of removal for WBB is much less compared to most technology-based removals present in the market. One research estimates the cost to be around $10 to $50 per ton of CO2 removed while another estimates it to be $14 per ton of CO2. Although there is a lack of consensus, it is generally agreed that the costs would be well below $100 per ton of CO2 removed.

Challenges

Despite the many merits of this process, there are some drawbacks. If the burial site or the choice of the biomass is not carefully planned and executed, it can lead to decomposition. Moreover, inaccessibility to the burial chamber and lack of effective monitoring can also risk the successful implementation of WBB.

However, such risks can be mitigated through efficient planning and deployment. The climate emissions from wood removal, transportation, and burial must also be carefully considered. Moreover, like a lot of nature-based solutions, it may be difficult to accurately quantify the CO2 removal achieved from this process.

Other concerns are related to the acquisition of biomass as there is a potential danger that large-scale implementation of WBB could eventually encourage the excessive removal of trees, beyond what is essential for fire prevention or the well-being of ecosystems. The obstacles with respect to the acquisition of biomass for WBB are similar to the hindrances faced by tech removals like BECCS and biochar.

All these removal methods suffer with the problem of overdependence on biomass for carbon sequestration. Moreover, BECCS produces energy while biochar can act as a soil enhancer, providing co-benefits that WBB lacks. However, the cost estimates of WBB are much lower than those of BECCS and biochar. Unlike BECCS, WBB also doesn’t have any concerns associated with environmental degradation.

Conclusion

Although there isn’t a lot of demand for it in the market yet, woody biomass burial shows great potential due to the multiple advantages it offers. It is a safe and scalable carbon removal solution which can sequester carbon at a much cheaper price than its counterparts. Although there are some hindrances to its effective implementation, these can be mitigated as it gains more recognition and greater research is undertaken.