On-farm production increased from biochar boost

THE benefits of biochar in agriculture are increasing, as more trials are undertaken.

Climate Agricultural Support consultant Melissa Rebbeck, Goolwa, SA, who has worked with the "charcoal-like substance" since 2014, outlined a number of these benefits during a recent agtech bus tour across the Fleurieu Peninsula.

"Biochar production and its effect on soil and animal health is some of the most exciting work that I have done," she said.

"There is about 10 million tonnes of biomass that is burnt or goes into landfill every year producing 15mt of CO2.

"Much of this biomass could be turned into biochar via a process called pyrolysis.

"When processed correctly, pyrolysis captures everything, including energy emissions, and we can reuse everything, from bio-oil, bio-gas, bio-diesel, wood vinegar.

"The heat energy that you can capture can be used for power generation.

Biochar is up to 90 per cent carbon, but the heating process in the absence of oxygen means that it is very special because it activates it.

"Then everything else that remains is carbon. Depending on the length of the burn and heat, will determine the quality of the biochar.

"Biochar is up to 90 per cent carbon, but the heating process in the absence of oxygen means that it is very special because it activates it."

Ms Rebbeck said one gram of biochar was the equivalent of the surface area of a house.

"It is highly porous and has a large cation and anion exchange capacity across its large surface area," she said.

"When used in soils, plants or animals, those anions and cations act like a battery, waking up minerals and nutrients becoming more absorbable.

"Feed becomes more actively absorbed, resulting in better feed conversion. Soil health is improved, as is pasture minerals and productivity."

Ms Rebbeck, who is also a director of the Australia and New Zealand Biochar Industry Group, said a roadmap was being produced that outlined a pathway to work toward pyrolysis of that 10mt to make biochar. It will also contain an agricultural component.

"Australia's soil carbon is at an all time low, with some scientists saying we only have 10 years left of growth out of the topsoil," she said.

"However for every 1pc we increase soil carbon, we increase water holding capacity by 10-30pc and production by 10-30pc," she said.

"We need to get carbon back into the soil.

"Biochar is carbon and the making of biochar recycles carbon back to the soil rather than losing it to the atmosphere and increasing climate change impacts."}

MORE RESEARCH UNDER WAY

A South Australian trial on the property of dairy farmer Barry Clark, Myponga, SA, has had Climate Agricultural Support feed biochar to dairy cows for a year at 150 grams per head a day.

Melissa Rebbeck said there were positive results.

"Starting in January, we noticed an immediate increase in milk yield," she said.

"Starting at 14-16 litres per cow per day, by the end of the trial some animals were up to 20.5L/cow/day.

"Milk solids also improved by 0.01kg/hd/day.

"We also noticed a decrease in the need for feed, up to two round bales per week.

"Taking away the biochar cost (about $1000/t), we saw an increase in profit of $30,000 just by feeding that 150g of biochar a day."

Ms Rebbeck said they planned to undertake more research on both soil health benefits and whether biochar could even help reduce cow methane emissions.

"Biochar does not get digested by the animals, it remains in the manure, and is highly bioactive," she said.

"Fifty cows produce about 1t of dung a day, so for someone with 250 cows, that's 5t of dung a day or 1825t a year.

"Across 200ha, that's a spread rate of 9.1t/ha of activated manure."

Ms Rebbeck said the Fleurieu had a good population of dung beetles, which had been reburying the activated biochar manure.

"We have tested some of that soil and found some extraordinary results, in increased mycorrhizal fungi, increased soil carbon and unlocked phosphorus," she said.

"So not only is there a potential carbon credit payback for the farmer, they're also increasing soil carbon, their water holding capacity by 10-30pc, and production by 10-30pc.

"We have also found increases in pasture biomass, and have also conducted trials containing biochar and superphosphate, which resulted in greater yields than using just super alone or biochar on its own."

Ms Rebbeck said they were also looking into mixing biochar with lime or gypsum.

"Lime may be our first port of call as SA has lots of acid soils," she said.

"By using biochar, it keeps lime in the soil for longer, potentially expanding its worth to up to 15 years, while biochar itself can last up to 1000 years and also has a pH neutralising effect.

"Mixing it with gypsum could also prove beneficial to local calcareous soils."

Source: Alisha Fodgen, Farmonline National, 20 September 2022