End of the Line – Approaches and insights to Timber Waste Management

Effective end-of-life strategies are crucial to ensure that the carbon sequestered in timber remains stored and does not contribute to atmospheric greenhouse gases. This article delves into the various end-of-life scenarios for timber and explores preferred outcomes in timber waste management, highlighting innovative approaches and sustainable practices that can help create a greener future.

Embodied Energy in Building Production

Embodied energy refers to the total energy consumed by all processes associated with the production of a building. This includes everything from the mining and processing of natural resources to manufacturing, transport, and product delivery. Notably, embodied energy typically excludes the energy used during the building's operational phase and the disposal of building materials at the end of their life. Existing wood products that are being demolished and disposed of when older buildings are redeveloped are usually also not included in the embodied energy assessment.

Different countries have varying points at which they assess the carbon lifecycle and embodied carbon of a building, but a comprehensive approach involves looking at the Life Cycle Assessment (LCA). LCA evaluates the environmental impacts of a product throughout its entire life cycle, from raw material extraction to disposal. This holistic view is crucial for understanding the sustainability of buildings and materials, such as mass timber and timber in general, especially when considering their end-of-life disposal.

A more linear graphic presentation above shows that embodied carbon can be calculated at the back end of the process, but this is a forecast at best, with the final outputs being more variable. The timeline spans 50 to 100 years away, making it challenging to forecast accurately due to many unknowns, especially as methods, technologies and government approaches for recycling evolve significantly over this period.

The percentage of embodied carbon varies significantly depending on the resources of the country. Generally, 50-80% of a building's life cycle carbon footprint can occur within the first production and construction stage. The final end-of-life phase accounts only for a smaller portion of the carbon emissions.

Most energy savings are made during the product phase. However, with advances in technology and more efficient production, energy savings are expected to reduce even further during the front end. With most of the focus on the front end, without ongoing proper management of the back end of timber disposal, the same level of reduction or drive for improvement may not be realised, which is a wasted opportunity.

When performing a Lifecycle Assessment (LCA) on wood products, it is essential to consider all stages of the wood's life—from extraction through to disposal. This approach includes carbon sequestration during the growth phase of trees, emissions from harvesting, processing, and transportation, as well as the use phase and end-of-life processes.

Appropriate Timber Sourcing

Timber from new growth plantations, which are managed appropriately, is recommended over timber from old growth forests where established ecosystems are destroyed. Old growth forests have accumulated significant vegetation layers and act as massive carbon sinks, so removing these trees will lead to detrimental environmental issues.

Certification systems like the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC) ensure that wood products come from responsibly managed forests, whether from old growth or plantations. These certifications ensure the timbers sourced are carbon neutral or environmentally beneficial.

When installing a mass timber structure and/or demolishing a derelict 50-year-old building, the sustainability around timber management is approached in vastly different ways and at different stages in the works. The mass timber might be sustainably sourced, but it is probable that a LCA was not completed on the removed timber. Sustainability consultants and architects were likely not involved in making the demolition carbon neutral. Instead, a quantity surveyor likely calculated the cost of waste disposal to landfills or recycling yards.

If the timber is not appropriately disposed of, this can offset the initial carbon sequestration from timbers used 50 years ago in the original build, negating the benefits gained during the new build from sustainable sourcing etc.

End of Life Scenarios

Complete reuse of timber

To truly sequester carbon, it is essential to focus on the complete reuse of timber products. For instance, maintaining a wooden beam as a wooden beam preserves its carbon storage capacity. When timber is repurposed into products like particleboard or paper, there is a loss of energy and carbon, making the process more of an energy cascade rather than a closed-loop cycle. This approach highlights the need for a circular economy where materials are reused and recycled in ways that maintain their integrity and carbon storage potential.

To facilitate this recycling and with most recycling approaches, proper segregation of building materials is key to the end-of-life stages for enabling beneficial reuse, recycling, and appropriate landfilling.

Recycling timber

In Australia, the recycling of industrial timber mainly involves converting it into woodchips or mulch. While this does recycle the material, it also reintroduces carbon back into the atmosphere as the wood decomposes, a factor often overlooked by builders who consider wood use as carbon neutral. Green Star Ratings System incentivises sending timber to recyclers, diverting waste from landfills. But woodchipping of timber products still results in carbon emissions released from decomposition.

The current waste legislation in Australia adds challenges, as timber contaminated with hazardous substances like asbestos, copper chrome arsenate (CCA), or creosote must be landfilled. In these environments, timber breaks down into CO₂ and methane – which is 28 times more potent as a greenhouse gas compared to CO₂. This highlights the need for better waste management practices.

Landfill

Landfill methane emissions can persist for over 60 years, peaking around the 30-year mark, making landfills the third highest contributor to methane emissions. Sending timber to landfills is particularly harmful as it produces both carbon dioxide and methane, while also filling up landfill space.

This underscores the importance of diverting timber waste from landfills as a crucial aspect in timber waste management. Doing so not only saves significant costs but also reduces environmental impact. Even a small reduction in timber waste going to landfills can have a substantial positive effect on the environment. Therefore, landfilling should be the last option.

Strategies for End-of-life (EOL)

• Energy recovery: Timber waste can be used as a biofuel to generate energy, replacing fossil fuels. This process is particularly useful for treated timber that is difficult to recycle due to chemical treatments. By converting timber waste into energy, it not only reduces waste but also contributes to renewable energy sources.
• Circular economy: Embracing a circular economy approach involves designing timber products with their end-of-life in mind, ensuring materials can be reused or recycled efficiently. The circular economy aims to keep materials in use for as long as possible, extracting maximum value and minimising waste.
• Research and development: Ongoing exploration of new technologies and methods for recycling and reusing treated timber. This includes developing processes to safely remove or neutralise chemicals used in timber treatments, making it easier to recycle treated timber.
• Material design: Ensure the use of appropriately sourced timber and design materials from the start to be beneficially reused at the end of their lifecycle.

Effective waste management policies and regulations are essential for supporting sustainable practices, including setting waste reduction targets and providing guidelines for safe disposal and recycling of treated timber. Regulatory support fosters innovation and ensures adherence to sustainable practices, aiming to enhance the timber industry's sustainability, reduce environmental impact, and create new economic opportunities.

Beyond an enabling regulatory framework, effective end-of–life management does require a collaborative effort across the ecosystem. A holistic approach is needed. From setting the right financial incentives to encourage or discourage certain behaviours, to having the awareness and willingness from project and asset owners, to combining technical expertise in sustainability, engineering, and technology to develop cost-effective, sustainable solutions that meet regulatory requirements and protect health and the environment, all stakeholders have a key role to play.

At Ramboll, we are dedicated to sustainable timber waste management and advancing the circular economy, with our innovative approaches and research demonstrating the potential of recycled timber to significantly reduce carbon emissions. Our work addresses challenges in waste legislation and contaminants, advocating for better waste management to prevent timber from decomposing into harmful gases in landfills. Please reach out to our experts to discuss how we can support you with your projects.