Australia has a food waste (FW) problem of staggering proportions. Each year, the nation generates approximately 31.2 million tonnes (Mt) of food waste across the entire supply chain. This isn’t just a missed meal; it’s a massive economic and environmental drain, costing the Australian economy $36.6 billion (AUD) annually. This waste also consumes 2,600 gigalitres of water and is responsible for 3% of the country’s total greenhouse gas (GHG) emissions. A comprehensive review by Piyal Chowdhury and colleagues, published in the journal Carbon Research, examines how Australia could turn this costly problem into a sustainable solution for its economy and environment: converting food waste into biochar. Currently, much of this waste ends up in landfills, where it’s expensive to manage and releases methane, a greenhouse gas far more potent than carbon dioxide. Other options, like composting or anaerobic digestion, have limitations, such as requiring substantial space or high setup costs.

The authors argue that a thermochemical process called pyrolysis offers a more effective path forward. Pyrolysis involves heating organic materials like food waste to high temperatures (typically 300−800∘C) in a controlled setting with little to no oxygen. This process chemically transforms the waste rather than just burning it. It breaks the material down into three useful products: bio-oil (a potential fuel), syngasSyngas, or synthesis gas, is a fuel gas mixture consisting primarily of hydrogen and carbon monoxide. It is produced during gasification and can be used as a fuel source or as a feedstock for producing other chemicals and fuels.   More (an energy-rich gas), and, most importantly biochar. This technology offers a way to not only manage waste but to create a valuable product that directly addresses two of Australia’s other significant challenges: poor soil quality and climate change.

Biochar’s first major benefit is its power as a soil conditioner, a critical need for a continent known for its low-fertility soils. When biochar is added to farmland, it acts like a high-end apartment complex for soil microbes and nutrients. Its highly porous structure helps the soil retain significantly more water and nutrients, like nitrogen and phosphorus, preventing them from washing away. It also increases soil organic carbon (SOC), which is vital for soil health and texture. This is particularly urgent as climate change threatens to degrade soils further; projections for New South Wales, for example, show a potential loss of 2.5-5.1 tonnes of SOC per hectare by 2070. The review points to studies where biochar from fruit and vegetable waste has increased SOC by 88-90%, directly combating this degradation.

Perhaps its most exciting application is in the fight against climate change. The pyrolysis process effectively locks carbon—which would have otherwise been released into the atmosphere as CO2​ or methane—into the stable, solid form of biochar, where it can remain sequestered in the soil for long periods. This turns a carbon source (rotting food) into a carbon sink (stable biochar). Furthermore, agriculture is a major source of Australia’s GHG emissions, particularly methane and nitrous oxide (N2​O). The review highlights research showing that applying FW-derived biochar to fields can dramatically reduce these emissions. One study found that biochar from banana peels cut CO2​ emissions by up to 42.2% and N2​O emissions by an impressive 35.48-54.54% compared to adding the raw waste to the soil.

Of course, the process is not without its challenges. The authors note that the high water content of food waste means it must be dried before pyrolysis, an energy-intensive step. The quality of the final biochar also depends heavily on the process parameters; a lower temperature, for instance, generally produces a higher yield of biochar. The review also cautions that some FW-biochars can have high concentrations of soluble sodium or ammonium, which could potentially inhibit soil organisms, indicating a need for further research to optimize the final product. Ultimately, this review presents a compelling case for biochar as a cornerstone of a circular economy. It transforms a 31.2 million-tonne waste stream from a multi-billion-dollar liability into a valuable asset that can heal soil, sequester carbon, and help Australia meet its ambitious goal of halving food waste by 2030.

Source: Chowdhury, P., Chowdhury, T., Chowdhury, H., & Bontempi, E. (2025). Food waste to biochar; a potential sustainable solution for Australia: a comprehensive review. Carbon Research, 4(41).