Recycled organics a growing prospect for healthy soil

Recycled organic material is an emerging industry with benefits on both sides of the fence, promising a productivity to farmers and a commercial use for the mountains of urban waste going to landfill.

“This stuff is called waste, organic waste, which creates a mindset the we need to get rid of it,” said Martin Towers, executive director of the Australian Organic Recycling Association.

“But if you start looking at it as an organic resource that is being wasted your attitude changes and you look for a beneficial reuse.”

State governments are developing programs to increase collection of organic material, but it is early days.

For farmers, recycled organic matter (collected by local councils in household bins, comprising green garden material and discarded food) can be used to help address soil-induced productivity problems such as low organic matter and nutrients, poor moisture infiltration and retention, hardsetting, erosion and compaction.

Mr Towers’ organisation promotes commercial processing of organic material. 

There are a range of different grades of recycled organic material, from nutrient-rich poultry manure to cheaper offerings that are best used to add only organic matter.

Many European countries have high rates of recycled organics usage. In the US, Californian farmers can’t get enough of it, with demand outstripping supply.

Down Under each state has their own regulations.

NSW has some of the most stringent standards. It requires green organic waste to be pasteurised with heat treatment, heated to 55 degrees Celsius for at least three days. Biosolids (treated sewage) and food must be held at the same temperature, but for a minimum of 15 days. Processing facilities must meet screening standards to achieve minimum levels of problematic material, such as glass and plastics.

Local processors compost what sounds like a whopping amount, six million tonnes a year, of regulated organic material. But that is less than one third of the current organic output.

Australia-wide, about 20mt of organic material is collected, meaning 13mt of organic material is wasted in landfill.

But even if farmers did cotton-on to recycled organics and tapped the full supply, 20mt would not spread far.

Mr Towers used broad averages to give an indicative example of the national demand.

He said an average 1ha of land needs an extra 50t of composted garden organic material to hit the healthy soil benchmark of 5pc organic matter.

As the top 10 centimetres of benchmark healthy soil in 1ha weighs 1200t, each hectare carries 60t of organic matter.

But most Australian soils fall short of optimum levels, with just 3pc or less organic matter, due to naturally low levels or historical practices. That means they are at least 25t underdone.

Recycled organic household material composts into organic matter at 2:1 ratio. 1t of household organic material delivers 500kg of organic matter (50t of material is required for 25t). 

Therefore the 20mt national harvest of organic material, reduced by half into organic matter, would not go far spread over the 384 million hectares of farmland recorded by the Australian Bureau of Statistics.

Mr Tower said education was key to increasing demand, and in turn expanding the supply pool. Currently, organic material is not collected from commercial premises, nor most high-rise residential developments.

“Raising demand will create a shortage, push the price up and attract new suppliers to the market to fill the demand,” he said.

Australian Soil Management is a Canberra-based recycled organics consultancy which conducts trials for farmers and works with the state regulator, the Environmental Protection Authority, developing standards and guidelines for the emerging recycled organics industry.

Chief executive Greg Bender has overseen trials on 10 farms, including grazing, cropping, almonds and viticulture.

He said initial usage of recycled organic material falls over time, and the biggest benefit came in rainfall retention.

“We are trying out farming different systems to see where and how to best fit recycled organics.”

“Generally speaking, it will take somewhere between three to five years to get organic matter in the soil to a good level.

“When it is at a reasonable level, it is just a matter of topping up. It’s not like fertiliser, you don’t need ot keep putting the same rate of fertiliser.

“The big driver is soil moisture. An extra 2pc organic matter in the top 30cm of soil is worth 15-20 millimetres of rainfall storage. Rain runs in, it doesn’t run off.”

With trials over the past two years, Mr Bender said the best results in terms of yield came from grazing, where dry matter in pasture increased 48pc. In a canola trial, where both recycled organics and fertiliser were used in tandem, oil content rose 20pc. In a wheat trial, also with fertiliser, protein went up on grade.

The fertiliser industry is a major challenge to the recycled organics market. 

“We are up against a very well established which is represented widely in retail stores. We need to prove that these things work. If the agronomist doesn’t understand it, and says it’s rubbish, we’ve got little hope.

Regulations vary from state to state, with a variety of certifications on offer. Experts agree users should require their supplier to a demonstrate their certification, and to seek independent advice to ensure products suit their needs.