Waste that could help mitigate climate change

Biochar can increase crop yields in poor soils and help halt the effects of climate change, study finds. So why don’t we use it more?

A product made from urban, agricultural and forestry waste has the added benefit of reducing the carbon footprint of modern agriculture, according to an international study involving UNSW.

Visiting professor at the School of Materials Science and Engineering at UNSW Science, Stephen Joseph, says the study published in GCB Bioenergy provides strong evidence that biochar can help mitigate climate change.

“Biochar can draw carbon from the atmosphere into the soil and store it for hundreds or even thousands of years,” says the lead author.

“This study also found that biochar helps build organic carbon in soil by up to 20 percent (on average 3.8 percent) and can reduce nitrous oxide emissions from soil by 12 to 50 percent. , which increases the climate change mitigation benefits of biochar. “

The findings are supported by the recent special report of the Intergovernmental Panel on Climate Change on Climate Change and Land, which found that there was significant climate change mitigation potential available through biochar. .

“The intergovernmental panel found that globally, biochar could attenuate between 300 million and 660 million tonnes of carbon dioxide per year by 2050,” said Professor Joseph.

“Compare that to Australia’s emissions last year – around 499 million tonnes of carbon dioxide – and you can see that biochar can absorb a lot of emissions. We just need a will to develop it and use it. “

Stable charcoal

Biochar is the product of heating biomass residues such as wood chips, animal droppings, sludge, compost, and green waste, in an oxygen-poor environment – a process called pyrolysis.

The result is a stable charcoal that can reduce greenhouse gas emissions, while increasing soil fertility.

the GCB Bioenergy The study looked at around 300 articles, including 33 meta-analyzes that looked at many of the 14,000 biochar studies that have been published over the past 20 years.

“He found that average crop yields increased by 10 to 42 percent, heavy metal concentrations in plant tissues were reduced by 17 to 39 percent, and the availability of phosphorus to plants also increased,” said Professor Joseph.

“Biochar helps plants resist environmental stresses, such as disease, and helps plants tolerate toxic metals, water stress, and organic compounds such as the herbicide atrazine.”

Benefits for plants

The study details for the first time how biochar improves the root zone of a plant.

In the first three weeks, when biochar reacts with the soil, it can stimulate seed germination and seedling growth.

Over the next six months, reactive surfaces are created on the biochar particles, improving the supply of nutrients to plants.

After three to six months, the biochar begins to “age” in the soil and forms microaggregates that protect organic matter from decomposition.

Professor Joseph says the study found that the greatest responses to biochar were in acidic, sandy soils where biochar had been applied with fertilizers.

“We found that the positive effects of biochar were dose dependent and also depended on how well the properties of the biochar match the soil constraints and the nutrient requirements of the plants,” explains Prof. Joseph.

“Plants, especially in low-nutrient acidic soils common in humid tropics and subtropics, such as the north coast of New South Wales and Queensland, could benefit greatly from biochar.

“The sandy soils of Western Australia, Victoria and South Australia, especially in arid regions increasingly affected by drought due to climate change, would also benefit greatly.”

Professor Joseph AM is an expert in the production of stable biochar from agricultural, urban and forestry residues.

He has been researching the benefits of biochar in promoting healthy soils and fighting climate change since it was initiated by native Australians in the 1970s.

He says biochar has been used for crop production and for maintaining healthy soils by indigenous peoples in Australia, Latin America (especially in the Amazon Basin) and Africa for hundreds of years.

Biochar was also registered in the 17th century as a food supplement for animals.

But while Australian researchers have been studying biochar since 2005, it has been relatively slow to take off as a commercial product, with Australia producing around 5,000 tonnes per year.

“This is in part due to the small number of large-scale demonstration programs that have been funded, as well as the lack of knowledge of farmers and government advisers on biochar, regulatory barriers and the lack of venture capital and young entrepreneurs to finance and create biochar companies, ”explains Professor Joseph.

In comparison, the United States produces about 50,000 tonnes per year, while China produces over 500,000 tonnes per year.

Must be economically viable

Professor Joseph, who has received an order from Australia for his work in renewable energy and biochar, says that to enable widespread adoption of biochar, it must be easily integrated into agricultural operations and demonstrated to be economically viable.

“We did the science, what we don’t have are sufficient resources to educate and train people, to organize demonstrations so that farmers can see the benefits of using biochar, to develop this new industry, ”he says.

However, that is slowly changing as large companies buy Carbon Dioxide Reduction Certificates (CORCs) to offset their emissions, which is boosting the profile of biochar in Australia.

Biochar has potential in a range of applications.

Professor Joseph co-authored a recent study in International Materials Reviews which detailed lesser-known uses of biochar, as a building material, to reduce toxins in soil, grow microorganisms, in animal feed and soil remediation.

UNSW has a collaborative grant with a company and a university in Norway to develop a biochar-based antimicrobial coating to kill pathogens in water and find use in air filtration systems, says he.