From Reuse To Burial: Managing Mass Timber Beyond The Building Stage

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Mass timber has become a leading candidate for reducing the carbon footprint of construction. Its appeal lies in the way it displaces high emission materials like concrete and steel, and in the fact that it carries biogenic carbon stored from the atmosphere into buildings. That carbon advantage is only secure if we think ahead to the end of life of these structures. The question is whether the wood will remain a carbon store or whether it will revert to being another emission source. Effective end of life strategies will determine whether mass timber truly functions as a climate solution or whether it is only a temporary pause in the carbon cycle.

This is one of the later articles in my series examining the role of mass timber in Canada’s housing and climate future, and by extension the rest of the world. The first piece laid out Canada’s timber moment, framing cross-laminated timber (CLT) and modular construction as the fastest lever for addressing housing shortages, jobs, and embodied carbon. The second explored how Mark Carney’s housing initiative could industrialize the sector through pre-approved designs, offtake contracts, and regional factories. The third explored the requirement for vertical integration within the industry to maximize efficiencies. The fourth showed how CLT displacement could bend the demand curves for cement and steel, making their decarbonization pathways more realistic. The fifth demonstrated that from harvest to housing, CLT already locks away more carbon than it emits, strengthening its climate case.

The sixth turned to the forestry supply chain, arguing that electrification of harvesting, transport, and processing is essential to maintaining CLT’s carbon advantage. The seventh piece addressed systemic barriers, focusing on high insurance costs and bespoke code approvals, and argued that normalizing mass timber in regulatory and financial frameworks is the key to scaling. The eighth piece, arguably one that should have been much earlier in the series, explored the various technologies in mass timber and its currently dominant form, CLT. The ninth piece assessed the global leaders, opportunities and competition for Canada’s mass timber industry and considers lessons to learn. The tenth piece deals with input regarding labor and financing I received over the course of the series from professionals engaged in the space. The eleventh piece focused more on a speed and labor opportunities that mass timber construction has demonstrated. The twelfth turned to carbon accounting and international standards. This article turns to the subject of end-of-life final resting places for mass timber, something introduced in the previous piece.

Biogenic carbon accounting is straightforward in principle. When a tree grows it absorbs carbon dioxide and stores it as carbon in its wood. When that wood is cut and used in a building, the carbon remains locked away. If the wood is burned or decays, the carbon is released as CO₂ or, worse, as methane if it breaks down anaerobically. Climate policy looks at these flows over a 100 year period. If carbon is held out of the atmosphere for that span, it is counted as a durable climate benefit. That is why strategies that extend the life of wood in use, or transform it into forms that decay extremely slowly, are important.

The most effective path is to design for disassembly so that timber can be directly reused. Panels and beams can be recovered intact if connectors and joints are chosen carefully. Some projects have already shown that this is possible, with cross laminated timber panels removed from test buildings and incorporated into new structures without loss of performance. If a building can last 50 years and its components are reused for another 50, then the carbon is locked away for a full century. The reuse option also avoids emissions from producing new materials, a benefit that shows up strongly in life cycle assessments.

If direct reuse is not possible, cascading uses offer another path. Beams and panels can be downcycled into smaller components, furniture, or composite products. Eventually, when the structural value is gone, the material can be chipped and made into particleboard or insulation. Each of these steps keeps the carbon in service longer. Cascading is less efficient than reuse but still valuable. It delays the release of carbon and reduces demand for virgin material, cutting emissions in upstream supply chains.

When the material can no longer serve in construction, there are options to transform it into more stable forms. Biochar is one of the most established. By heating wood in the absence of oxygen, a carbon rich char is produced that resists decomposition for centuries. Studies of ancient soils prove that charred biomass can remain intact for more than a thousand years. Adding biochar to soils not only locks away carbon but often improves fertility and water retention. Biochar can also be incorporated into concrete or asphalt, embedding the carbon in long lived infrastructure. The cost of biochar production has fallen quickly, with credits in voluntary carbon markets now in the range of $100 to $150 per ton of CO₂ sequestered, and there is potential for further reductions as plants scale up.

Another path is bioenergy with carbon capture and storage. In this approach waste wood is combusted to produce energy and the CO₂ is captured from flue gases and injected into geological formations. The energy can displace fossil fuel use while the captured carbon remains underground for thousands of years. Capture technology is proven at industrial scale and geological storage has shown high permanence. The barrier is cost, currently in the $100 to $200 per ton CO₂ range for most biomass facilities, but policies in places like the UK and US are beginning to close that gap, with 45Q for carbon sequestration persisting under Trump. For Canada, where pulp mills and biomass power already exist near potential storage reservoirs, this could be a natural extension of existing industries.

A variant of this is thermolysis to produce biocrude for the required biofuels for longer haul aviation and shipping. While the biogenic carbon would be released, it would have delivered extraordinary amounts of value through a very long life before that occurred, and that should be considered in accounting systems. A related alternative is biodigesters to create methane, a necessary feedstock for direct reduction of iron, manufacturing of methanol and very long-duration strategic energy reserves. A couple of those can have carbon capture bolted on as well.

Engineered burial is another option under discussion. The concept is to place wood in dry, oxygen free vaults underground so that it does not decompose. Properly designed, these vaults can retain more than 99 percent of carbon for over a hundred years. The costs are estimated at $100 to $200 per ton CO₂ today, with potential to fall as projects scale. A pilot project in North America has already been credited by a voluntary registry, showing that the approach is feasible. Concerns include ensuring that nutrients are not stripped from ecosystems by diverting too much biomass, and making sure vaults remain secure over centuries.

Some have proposed sinking biomass in the deep ocean, where low oxygen and cold conditions slow decay. In theory carbon could remain out of the atmosphere for centuries or millennia. In practice there are large uncertainties about environmental impacts, methane formation, and international regulation. At present, this is best treated as an experimental pathway rather than a mainstream strategy.

The least effective option is conventional landfill. While some carbon remains stored in landfills, much of it decays, producing methane. Even with gas capture systems, a significant portion escapes. Methane has a global warming potential dozens of times higher than CO₂ over 20 years, making landfills a climate liability. Europe has already moved to ban landfilling of organics, and Canada and the US are under pressure to tighten methane regulations. Landfill may persist in the near term but should be phased out as better options become available.

Managing mass timber at end of life also requires mechanisms to enforce outcomes decades into the future. Material passports that record what timber is in a building and how it can be disassembled can make reuse practical. These tools ensure that commitments made now will be actionable when buildings are decommissioned.

A key principle in shaping policy for mass timber end of life, in my opinion, is that we should not burden the builders or owners of today with the full costs of disassembly and disposal that may occur half a century from now. If those obligations are placed entirely up front, they risk discouraging the adoption of better, lower carbon buildings in the present. Instead, the focus should be on lightweight mechanisms that preserve future options without raising barriers now, such as material passports that document what has been built.

One argument against imposing even small escrow costs on mass timber projects, something often suggested, is that it creates an uneven playing field. Traditional buildings made of concrete and steel have never been required to pre-pay for their end of life impacts, despite the fact that demolishing them generates large volumes of waste and emissions. To single out mass timber, a material that already carries clear climate advantages, and make its developers shoulder additional costs for future disposal would be inequitable. It risks slowing adoption of a better material by adding requirements that incumbents have never faced.

Another problematic approach is producer responsibility requirements, putting the creation of end of life management and solutions on mass timber manufacturers today for something that won’t be required for 50 years or more. Once again, this penalizes the already much better with fiscal responsibilities not borne by manufacturers of traditional and much more harmful materials.

A more balanced approach would be to establish broad policies that eventually apply to all construction materials, or to fund future recovery through collective mechanisms such as carbon markets or federal funding, rather than penalizing the very builders who are choosing lower carbon options today.

Global policy is moving in this direction. The EU and UK are embedding whole life carbon assessments in building codes, including end of life. New Zealand and Australia are setting embodied carbon caps that will force consideration of disposal. Canada has not yet formalized rules but has the opportunity to build on its forestry and biomass industries to lead. By supporting pilots in biochar, BECCS, and engineered burial, and by updating codes to encourage design for disassembly, Canada can ensure that its mass timber boom leads to long term carbon benefits.

By 2030, it is realistic to expect that reuse standards, biochar facilities, and perhaps one or two demonstrations of other approaches will be in place in Canada. By 2035, landfill of wood could be nearly eliminated, replaced by a mix of reuse, recycling, carbonization, and capture. If that trajectory is followed, mass timber buildings constructed today will not only cut emissions at the point of construction, they will remain climate assets a century from now. Effective end of life management is what will turn mass timber from a promising low carbon material into a reliable negative emission pathway.