Waste cooking oil from food establishments has been used to make a controlled-release fertiliser which results in less wasted nutrients and better plant health, reports The Lead South Australia.

The fertiliser uses waste canola oil and sulphur which is being used to form a degradable polymer coating to encase each fertiliser pellet.

Dr Justin Chalker and his team at Flinders University of South Australia developed the fertiliser at the Institute for NanoScale Science and Technology.

“You can use it [canola oil] for frying food and then you can use it again for something that’s used to grow more food,” said Dr Chalker.

“What’s unique about our material compared to other slow release fertilisers is the material that holds in the nutrients is made entirely from waste and we show in this paper that it can degrade, which is important for the long-term persistence of this material whether it’s in potted plants or the environment.”

Testing was carried out on tomato plants and showed the nutrients were released in a controlled fashion, resulting in less wasted fertiliser and better health for growing plants.

“What we’ve shown is these materials are excellent for preventing nutrient burn at the beginning of the growing cycle and you can control the release rate to match the plant’s needs, which is quite unusual, resulting in taller, greener and healthier plants,” said Dr Chalker.

Another benefit of the slow release was that it prevented fertiliser runoff, which protected is bad for the environment. An estimated 50% of fertilisers currently applied to crops were not used by the intended plants because of runoff and leaching, the report said.

Dr Chalker announced that larger scale trials would now go ahead to see if other similar fertilisers could be produced for other crops. He said that the polymer could be made from other plant-based oils such as sunflower oil or olive oil as long as they were unsaturated.