Innovative biochar research program explores application for carbon sequestration

In a bid to bolster innovative and circular approaches to broad-scale carbon sequestration, one leading Australian water-energy research team is exploring the design and application of customised biochar to enable soils to retain more water and store more carbon.

Deakin University’s Water-Energy Nexus Research Group has been focusing on various studies and assessments of the application of biochar to soil, including the best waste materials to use to create biochar products that are highly absorbent and resilient.

While biochar application has many benefits, including the reuse of organic waste streams and regeneration of soil health, Deakin University’s Professor Wendy Timms said there is big potential for the approach to help lower carbon levels in the atmosphere.

“From a carbon point of view, we know we need to avoid emissions, reduce emissions and remove emissions. We have gotten to the point with accumulated carbon in the atmosphere that we need to not just reduce it, but also remove it,” she said.

“We need to get a lot of carbon back down into the geosphere – the soil, rocks and deep geological traps. There are several ways to do that. We’ve got a number of engineering student projects going on involving the optimising and scaling-up of carbon removal or sequestration methods.

“We know from recent IPCC reports that this work needs to scale up very rapidly. It’s important to lean now towards methods that are relatively low-cost and ready to go, and that are stable and permanent.

“One of our avenues for doing this is via soil carbon and pyrolysis biochar. And it’s a method that has really positive implications for water.”

Water increases the ability for soil to sequester carbon, Timms said, which is why focusing on improving moisture retention is key.

“We know that to boost the natural soil carbon, we also need the soil to be moist. If it dries out, we can lose carbon too,” she said.

“With farming, we risk loss of soil carbon. We end up with a dry landscape with lower carbon storage. If we can bring good structure and health back to the soil, we’ll have better carbon and water storage, which leads to all sorts of benefits for farming and the environment.”

Designing biochar

Included in Deakin University’s biochar research portfolio is the output of PhD candidate Sirjana Adhikari, whose project focused on designing biochar production to maximise water availability and carbon sequestration potential, and also improve soil properties.

“Biochar is made by heating the waste biomass from 300 to 900 degrees celsius, in a limited oxygen or no-oxygen environment. The process is called pyrolysis,” Adhikari said.

“Biochar has a charcoal like structure, which is what plays a very significant role in water and carbon storage.”

Adhikari’s project evaluated different commercial biochars, comparing how different types of biochar made from different types of biomass perform. She measured water and nutrient availability and also ability for carbon sequestration in in biochar mixes with sandy or clay loam soils.

“Not all biochar is the same. How it performs depends on what it's made from. My research has been about optimising biochar according to its intended end use. We can design different biochars for different applications to get the best outcome,” she said.

“Using woody biomass, like a fallen tree, creates a biochar with a very porous structure. This provides opportunities for water storage and for beneficial microbial growth encouraging soil porosity and aggregates, improving the soil quality, thereby improving the soil’s ability to store carbon.

“We found that this type of biochar can hold water more than 10 times its weight. It also releases the water very slowly, all because of the structure it has maintained from the original woody biomass.”

Adhikari said some forms of biochar produced from certain types of biomass are incredibly stable, and resistant to microbial and thermal degradation.

“If we apply it to soil, it will remain there for hundreds of years or more. It’s pretty amazing. We’re putting carbon back into the soil by pyrolysing biomass that would otherwise decompose and release more carbon into the atmosphere,” she said.

What’s next

While using biosolids alone to make biochar doesn’t produce the same level of water retention as using woody biomass, there are still benefits of further exploring this waste-stream option, Timms said.

“We have quite a few projects around how we can benefit the water industry, organic waste processors and agriculture, and we are really focused on the potential for bigger applications across the country,” she said.

“We are working with UNSW, Griffith University, biochar producers and end users of biochar.

Whether it’s our own Deakin University solar farm, or on degraded land or farming areas, we want to look at large-scale applications because that's where we can have a significant impact.

“It’s estimated that every 1% increase in soil organic carbon creates 10 to 30 tonnes per hectare of water storage. But we think we can do better than that using biochar and demonstrate how much water can be stored in various Australian soils.”

Timms said soil moisture retention is not only important for supporting the landscape during drought, it’s important for adapting to climate change.

“We know we will end up with drier landscapes, and that rainfall will come in bigger and more intense events. We want the landscape to be capable of storing as much of that rainfall, when and where it falls,” she said.

While demonstration is in the early stages, the research team are currently seeking industry partners and have seen some benefits of biochar application on Deakin University’s solar farm, even if only for the resident herd of sheep.

“Our 14-hectare solar farm also farms merino, and our sheep are very happy to sit in the shade of solar panels, and eat the greener grass,” Timms said.

“We are in the early stages of a demonstration at the Deakin solar farm, on our path to carbon-neutral. We are already seeing massive increases in soil moisture within our biochar trenches on our farm, but also spreading out around them.”

International leader in biochar research Professor Stephen Joseph said this is all about farmer-friendly solar.

“Biochar can improve solar renewable projects in lots of ways, and at the same time, benefit agriculture. All together, we can have carbon removal and water positive ways of making the food, fibre and energy that we need,” he said.