Biochar as a Sustainable Material in Remediation and Construction: Opportunities and Considerations

Introduction: why biochar is gaining attention in Australia

Across Australia’s development, infrastructure and remediation sectors, there is growing pressure to deliver projects that are not only compliant, but demonstrably sustainable. Developers, government agencies and industrial operators are increasingly looking for materials that reduce emissions, reuse waste streams and improve long-term environmental outcomes.

Biochar has emerged as one such material. Produced through the thermal processing of organic biomass in low-oxygen conditions, biochar is a carbon-rich, stable material that can be incorporated into soils and, in some cases, construction materials. Its appeal lies in the potential to combine biochar carbon sequestration, biochar soil improvement, waste reuse and emerging biochar construction applications.

From our perspective as environmental and contaminated land consultants, biochar represents an opportunity, not a shortcut. Its use must be informed by site conditions, material quality, contamination pathways, regulatory frameworks and engineering performance requirements. Understanding both its benefits and limitations is essential before adoption on any project.

Carbon sequestration potential at a project level

One of the most frequently cited benefits of biochar is its ability to lock carbon into a stable form for decades or centuries. Unlike untreated organic matter, which decomposes and releases carbon dioxide, biochar resists breakdown and can act as a long-term carbon sink.

At a project level, this has several practical implications.

What carbon sequestration means in practice

When biochar is incorporated into soil or construction materials, a proportion of the carbon originally captured by vegetation is effectively stored long term. This can contribute to lower life-cycle emissions for developments, particularly when biochar is derived from waste biomass that would otherwise decompose or be landfilled.

However, carbon sequestration benefits are not automatic. They depend on:

• Feedstock type and sourcing
• Production temperature and process control
• Intended end use and exposure conditions
• Transport distances and overall life-cycle assessment

In Australia, claims around carbon benefits increasingly require defensible evidence. While biochar may support emissions reduction narratives, it does not replace the need for robust carbon accounting or offset frameworks where required.

Limitations to consider

Biochar is not currently a regulated carbon offset in many project approval pathways. Overstating its sequestration value can create reputational and compliance risks. We advise treating carbon storage as a secondary benefit, not the sole justification for use.

Biochar soil improvement and land rehabilitation

The most established use of biochar globally is in soil systems. In Australia, interest in biochar soil improvement is growing across land rehabilitation, mine closure, brownfield redevelopment and some agricultural settings.

Where biochar can enhance performance

When appropriately specified, biochar can improve certain soil properties, including:

• Increased water holding capacity in sandy or degraded soils
• Improved soil structure and reduced compaction
• Enhanced nutrient retention, particularly when blended with compost or organic amendments
• Potential immobilisation of some contaminants, reducing bioavailability rather than total concentration

These characteristics can be valuable on disturbed sites where soil quality limits revegetation or post-remediation land use.

Where biochar may not be suitable

Biochar is not universally beneficial. In some contexts, it can introduce challenges, such as:

• Elevated pH levels that are unsuitable for certain vegetation
• Variable nutrient behaviour depending on feedstock and production method
• Inconsistent contaminant binding performance across different soil types
• Potential introduction of polycyclic aromatic hydrocarbons or metals if poorly produced

From a contaminated land perspective, biochar should never be assumed to “treat” contamination without site-specific validation. Laboratory testing, pilot trials and risk assessments are essential before use on sensitive sites.

Waste management and circular economy applications

Biochar is often promoted as a circular economy solution because it can be produced from organic waste streams, including forestry residues, green waste and some industrial by-products.

Reuse pathways and opportunities

From a waste management standpoint, biochar can:

• Divert biomass from landfill
• Reduce methane emissions associated with organic waste decomposition
• Create a secondary product for reuse in soils, landscaping or construction blends

For landfill operators and industrial facilities, this presents an opportunity to transform a disposal liability into a usable material, provided quality and compliance requirements are met.

Material quality considerations

Not all biochar is suitable for environmental or construction use. Key quality factors include:

• Consistency of feedstock
• Production temperature and residence time
• Residual contaminants or ash content
• Particle size distribution and structural integrity

Without clear specifications and testing regimes, biochar can introduce new risks rather than reduce existing ones. Quality assurance frameworks are critical, particularly where biochar is proposed for reuse on regulated or sensitive sites.

Biochar in pavement materials and construction

Interest in biochar construction applications, including biochar in pavement materials, is emerging within Australia and internationally. Research and pilot projects have explored its use as a partial replacement or additive in asphalt, concrete and unbound pavement layers.

Emerging applications

Potential construction uses include:

• Additive in asphalt mixes to reduce binder demand
• Filler material in pavement subgrades
• Lightweight aggregate replacement in low-load applications
• Soil stabilisation in selected earthworks

These applications are still developing and are typically limited to trials or non-critical infrastructure elements.

Engineering and durability constraints

From an engineering perspective, biochar introduces challenges that must be addressed before widespread adoption:

• Lower strength and stiffness compared to conventional aggregates
• Sensitivity to moisture and compaction methods
• Long-term durability and ageing performance
• Lack of standardised Australian specifications

Until performance is demonstrated under Australian conditions, biochar should be treated cautiously in structural or high-load applications. Any proposed use in pavements or construction must be supported by laboratory testing, design verification and asset owner acceptance.

Key environmental and technical considerations before adoption

Before biochar is incorporated into remediation or construction projects, a number of critical assessments are required.

Environmental risk and compliance

Biochar use must align with:

• Contaminated land regulations and guidelines
• Waste classification and reuse requirements
• Human health and ecological risk assessments
• Planning approval and conditions of consent

In some jurisdictions, biochar may be classified as a waste or fill material, triggering additional approvals.

Site-specific performance testing

No two sites are the same. Biochar performance is highly context dependent. We recommend:

• Site-specific soil and material testing
• Pilot trials where biochar is proposed at scale
• Monitoring plans to assess long-term behaviour

Supply chain and scalability

Reliable sourcing is often overlooked. Biochar supply can be inconsistent in volume and quality, particularly for large infrastructure or remediation projects. Early engagement with suppliers and contingency planning is essential.

Conclusion: opportunity with informed application

Biochar presents genuine opportunities across remediation, land rehabilitation and selected construction contexts in Australia. Its potential benefits in carbon sequestration, soil improvement and circular economy outcomes are well recognised. However, it is not a universal solution.

Successful use of biochar depends on rigorous assessment, material quality control and alignment with environmental, engineering and regulatory requirements. When approached strategically, it can form part of a broader sustainability and risk management framework rather than a standalone fix.

At Nova Group Pacific, we work with developers, councils and industrial operators to assess emerging materials like biochar in the context of contaminated land, environmental compliance and development risk. If you are considering biochar for a remediation or construction project, we recommend engaging early to ensure its use is technically sound, compliant and aligned with your project objectives.

Book a consultation with our team to discuss whether biochar is suitable for your site and how it can be responsibly integrated into your project strategy.