A workshop where Thabiso Mashaba shows Uawa residents how to create biochar. Photo: Supplied
Innovators across New Zealand are working on solutions for the huge amount of silt and woody debris that is clogging beaches and riverbanks on the East Coast.
Research into how silt can add nutrients back into the land is underway, and a project to turn slash into cash has being trialled with a community north of Gisborne.
When Thabiso Mashaba arrived in the northern Tai Rāwhiti town of Uawa in early March, cyclones Hale and Gabrielle had blown through in quick succession, leaving the region strewn with slash and silt.
As an Edmund Hillary Fellow, he was interested in helping the Tolaga Bay residents find their own solutions to local problems - as well as making sure they could be compensated for their work.
Slash to Cash was born.
According to Mashaba, the project involved taking some of the abundance of slash scattered across the region, and burning it in a sealed environment, which turned it into bio-char.
"It's controlled burning that's done in an enclosed container, and this keeps all the gases that could be going up, going back into the drum and burning, and then eventually they become part of the carbon, and form the charcoal that remains in the drum."
The charcoal could then be activated with something like animal urine, which made it a nutrient-rich fertiliser for soil.
"With the heavy flooding there's been a loss of nutrients [from] the soil, with that clear felling [of forestry plots] there's also been a lot of erosion of the soil itself, so what you then apply back as activated biochar will allow the land to heal."
The charcoal could also be turned into briquettes, which burned without smoke, making them perfect for indoor heating and cooking. Mashaba said they were popular back home for heating chicken houses in winter.
Slash to cash lead instructor Thabiso Mashaba (right) with design facilitator Matene Maraki. Photo: Supplied
The best part about the solution was that locals could do it themselves, with no more technical equipment than a metal bucket. Tutorial sessions were underway, and locals had expressed enthusiasm for a project that put the power back in their hands.
Ideally, it would provide a long-term solution and income stream. When - or indeed, if - the slash ran out, any dead organic matter could be used, Mashaba said.
Through the Wairoa District Council, he said they would soon be applying their bio char as fertiliser to a private orchard to test its effectiveness.
Back in Gisborne, Jacopo Orazi, an Italian agro-ecologist, had been analysing silt under a microscope.
"What I found was organic matter was missing, and organic matter is what allows plants to exist most of the time - those nutrients and those micro-nutirents - and at the same we found slash, which is organic matter, right? So I said, what if we combine the two?"
By composting them together, they created fertiliser, improving the quality of the soil and encouraging more tiny microbes to live in it.
These microbes tunnelled through the soil, aerating it and creating drainage. Orazi said he thought of them as "tiny engineers".
"They do all this work for us, creating stable structures in the soil to allow water infiltration, and also water retention."
This meant that when the next storm arrived, the ground would absorb a lot more water, rather than it sitting on top causing erosion and flooding.
At the moment, it was only an idea, presented to the Gisborne District Council in a recent report.
Kathy Liu is a masters student at Canterbury University and has been studying the effect of improving soil aeration with wood chips on plant growth. Photo: Supplied
But a similar project was underway at Canterbury University, by masters student Kathy Liu.
Using soil samples from Gisborne, she had been studying the effect of chipped pine slash on soil quality.
"What I'm doing now is to mix crushed pine waste and fertiliser with problem soil to improve the soil," she said.
It was using one challenging waste problem, pine slash, to fix another - that of poor soil quality, and worked by increasing aeration.
"The reason why this soil is horrible is that there were almost no pores in it, which means water can't flow out and air cannot enter the soil. So when you sow the seeds in, they will just suffocate and perish."
Tests on oats grown in a campus greenhouse had shown an increase in soil fertility, she said.
According to their creators, the next step for all of these projects was to get out there and test them in the field.
