22 September 2025 Luna's mission to understand biochar, the "superhero" material

Luna Nguyen wants to help change that. She’s a PhD student at Lincoln studying how we can make biochar from waste grape products more efficiently. She successfully presented her work at Lincoln’s Three Minute Thesis finals, which won her second place.

Biochar is an incredibly carbon-rich material made from organic matter. It’s made by heating biomass while depriving it of oxygen, a process called pyrolysis. Without oxygen the material can’t catch fire, leaving you with dense pure carbon instead.

But we’re lacking research on the best way to make it. Temperatures for pyrolysis can vary from 300°C to 900°C. Luna’s on a mission to find out which exact method results in the most effective biochar.

She’s focusing on grape marc, the solid remains leftover from grapes after pressing. It contains the skin, seeds, pulp and stems. New Zealand’s winemaking industry makes about 50,000 tonnes of grape marc every year.

“People have tried to turn grape marc into compost, but it takes time, labour and a huge amount of space,” Luna says. “It also produces greenhouse gas emissions, and it can leach into and contaminate soil and water.

“Most winemakers are paying to landfill it, but it costs a lot of money.”

Biochar is remarkably versatile. When added to soil it acts as a slow-release fertiliser, increases water retention and helps maintain a healthy pH level. It can help purify water from heavy metals, and it can be burnt as a fuel source. In the long run, biochar could play a vital role in climate change mitigation with its carbon sequestration capacity.

“It’s kind of a superhero.”

Converting grape marc to biochar reduces the total mass to one third, which means wineries would save significant space on storage as well.

Luna believes there is big potential for winemakers to profit from biochar, but at the moment production costs are too high. By studying the best conditions for pyrolysing grape marc Luna could help make it more accessible and normalise it within the industry.

She’s producing five different types of biochar, then adding it to soil around native plants. In time she’ll discover which grade of biochar worked best as a soil amendment and what impacts it had on the surrounding soil.

“It’s about the long-term story. I’m looking at a dream material that can fix a lot of things, but there’s a lot that goes into the financial side of things. I think we’ll have to wait and see.”