Australia – an ancient continent where good soils are in very short supply – is about to discover a new industry: making soil.

The new artificial soils will be made from wastes which other industries and sectors – including manufacturing, farming and urban waste – now throw away.

The key ingredients of a good soil include stable minerals and organic compounds that give it structure, porosity and fertility, says Professor Dick Haynes, who is heading up a major new research effort by CRC CARE to create soils.

“While you can buy bags of ‘soil’ at the garden centre today, they mostly contain composted green waste, which soon breaks down, subsides and eventually disappears,” he explains.

“There is no scientific standard for soil as such – no formula for making it.  Everyone has their own secret ingredients. Worldwide, very little research has been done into how you make a soil. Our aim is to come up with one.”

Furthermore, he says, some of Australia’s biggest waste challenges – 13 million tonnes of fly ash from power generation, an even larger amount of ‘red mud’ left over from bauxite processing, plus millions of tonnes of bio-solids from urban sewage systems – are all potential ingredients in artificial soils.

“At the moment people are paying to get rid of these things.  At CRC CARE we think we can formulate them into something useful which is currently in short supply and becoming quite expensive – new topsoil,” Prof. Haynes says.

Two of Australia’s greatest headaches are its millions of hectares of acid and sodic soils, both of which limit food production.  The ability to improve acid and sodic soils could greatly increase the nation’s capacity to grow food.

“Wastes such as power station or sugar industry fly ash can be highly alkaline and could be used to correct acid soils. Organic wastes such as chicken litter are also highly alkaline and could be used to add nutrients as well as correct acidity. Furthermore we think that – unlike lime – they will leach further into the soil profile, correcting acidity to a greater depth.
“Australia has millions of hectares of sodic soils – rich in sodium. To amend these you need a soil improver high in calcium, such as poultry waste, certain fly ashes or slag from steelmaking.”

Part of the key to successful soil-making is to avoid the high costs of transporting either the raw materials or finished soils around the country – this involves identifying wastes available locally which could go into a soil or soil improver.

Another original twist is CRC CARE’s plan to use certain industrial wastes to clean up other contaminated wastes.

“Many of these substances, like red mud, fly ash and slag have a very high adsorptive capacity.  We can literally use them to mop up heavy metals or organic contaminants from other wastes, rendering these safe to use as soils, building materials or other products.”

Professor Haynes says the growing interest in soil-making is causing people to reappraise what they once regarded as contaminated wastes, fit only to dump. Opportunities to invest in the CRC CARE soils research program are still open.

“You could well be looking at the ingredients for a major new industry.  It’s even conceivable we could re-import wastes from overseas industrial processes which used Australian raw materials such as coal and iron, to turn them into soils to beautify our cities or grow more food.”

Just as natural soils vary greatly, the composition of artificial soils will depend on what is available and cheap locally, from agriculture, food processing, heavy industry, power generation and urban waste disposal systems.

“There are hundreds of uses for these waste products, provided we can standardize the way they are treated, ensure they are completely safe and that their long-term effect in the environment is a beneficial one.  At present many of these questions remain unanswered.” 

Dick Haynes  is Professor of Soil and Environmental Science at the University of Queenland. He has worked as a senior soil scientist for the NZ Ministry of Agriculture and Fisheries and was until recently Chair of Soil Science at the University of Natal in South Africa.