Black gold: Farmers adopting ancient technique to help with modern environmental issues

On the cusp of gardening season, there is a soil additive alternative to poop and compost that stores nutrients and helps with droughts – and what’s more, it’s already in the backyard.

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The alternative soil additive is carbon that's been specially burnt and, like a sponge, it holds onto water, oxygen and nutrients. Source: Seven Sharp

Biochar is carbon that's been specially burnt to add to soil and, like a sponge, it holds onto water, oxygen and nutrients.

“It also provides a habitat for micro-organisms and that's fundamental for a soil,” said Biochar Network New Zealand's Dennis Enright.

His mountain of black gold is all waste from a nearby sawmill that would otherwise end up in landfill.

The key part of the burning equation is limiting oxygen.

“So, it's not no oxygen, but it's hungry for oxygen,” said Stardust Earth's Simon Day.

“If you had air coming from the bottom you’d be burning that carbon just as quick as you are making it.”

By itself, biochar has little nutrient value. It needs to be charged like a battery.

Mixing it with water and fertilisers makes it become a storage system for soil.

“It's really light. When we put the nutrients with it, they just do their thing," said Soil Conditioner Products’ Miles Pope.

“It turns it into slow-released fertiliser so it's not going down the drain.”

Down the drain is an accurate phrase, because biochar means the soil needs less water.

Jason Thomas of ST Growers has been adding biochar to his potato crop for five years.

“We're seeing a 40 to 50 per cent reduction in our commercial fertiliser bills,” Thomas said.

“All the biological activity that's going on in the ground is creating really healthy food.”

None of this is new. Biochar gardening is an ancient tool that's been lost to modern agricultural practices.

“Around the world 30 per cent of our productive soils are degraded. They’re not producing as much, they’re not able to produce as much and we have an increase in population,” Enright said.

These men are committed to spreading the word.

“Because not many people know about biochar and it happens to be one of the most important things in terms of the environment, economy, creating jobs, the whole nine yards. It can do it,” Enright said.

The big hope is that every bit of carbon that's sent back into the soil is saved from the atmosphere.