In a groundbreaking initiative, Macedon Ranges Shire Council partnered with RMIT University to conduct the world's first field trial of coffee biochar concrete in municipal infrastructure. Building on RMIT's laboratory research demonstrating up to 30% strength enhancement in concrete using biochar derived from spent coffee grounds, our council implemented this innovative material in a real-world footpath project in Gisborne, Victoria.
The field trial aimed to evaluate the performance of coffee biochar-enhanced concrete under actual construction and environmental conditions. A key challenge emerged early in the project: due to limitations in commercial pyrolysis equipment, we were unable to produce biochar at the optimal 350°C temperature identified in laboratory studies. Instead, we utilized biochar produced at 450°C as a partial replacement for fine aggregates in a standard N25 grade concrete mix. This deviation from the optimal conditions highlighted the practical challenges of translating laboratory innovations to real-world applications.
Independent testing was conducted on slump, compressive strength, flexural strength, and shrinkage properties. Results showed that the biochar concrete-maintained workability comparable to conventional concrete. While early-age compressive strength was slightly lower, long-term strength development showed promising trends. Notably, the biochar concrete exhibited an 18.9% increase in 28-day flexural strength and improved shrinkage resistance compared to the control mix, despite the suboptimal pyrolysis temperature.
This trial demonstrates the potential of transforming local coffee waste into a valuable construction resource, aligning with our council's sustainability goals. It also underscores the importance of addressing supply chain and equipment limitations to fully realize the benefits observed in laboratory settings. As we continue to monitor the long-term performance of this footpath, this project serves as a model for sustainable and innovative infrastructure solutions in local government, paving the way for wider adoption of waste-derived materials in construction while highlighting areas for further technological development in biochar production.