Environment
Are cheap plastics the new tobacco?
Degradable bioplastics offer a smart solution to nitrogen pollution
Wrapping fertilisers in degradable plastics is showing promise for increasing food production while reducing pollution
Published 18 March 2025
By 2050, we will need to feed almost 1.8 billion more people, when our global population reaches around 10 billion.
We have less land available for agriculture due to urban sprawl (and other competing needs), but we also need to avoid clearing more forested land for farms, while boosting crop production at the same time.
But we can’t afford the current environmental and health costs of using large amounts of synthetic (nitrogen-based) fertilisers.
Environmental cost of food production
As well as contributing to greenhouse gas emissions, soil acidification and biodiversity loss, inefficient use of nitrogen-based fertilisers leaves excess nutrients that leach into waterways, leading to algal blooms that suffocate aquatic lifeforms.
In the sugarcane growing region of Far North Queensland, this poses a major threat to the already fragile Great Barrier Reef ecosystem.
Nitrogen pollution of air and water also causes multiple human health problems, including respiratory diseases and some cancers. Despite all these issues, reducing fertiliser application is not always practical or acceptable for crop farmers.
The risk of not using fertilisers in a changing global environment is often not worth the loss in crop yields or prospective revenue for farmers.
Plastic coatings provide a solution (and pose another problem)
One solution is to coat fertilisers in a thin layer of plastic that slows release to better align with the needs and timing of plant growth, thereby reducing nitrogen waste and pollution.
However, these coatings degrade into long-lasting microplastics that run off into our waterways or are absorbed by crops, entering our food chain and our bodies.
Recent research has shown that microplastics can even cross the blood-brain barrier, and their accumulation in organs is implicated in a range of diseases.
There is no legislation in Australia that polices the use of plastic-coated fertilisers – which are readily available and sold at many garden and hardware stores.
The United Nations Environment Assembly is wisely seeking a global treaty to end plastic pollution. So, we urgently need alternative solutions to reduce nitrogen pollution while boosting crop production.
Since 2021, researchers in the multidisciplinary ARC Research Hub for Innovative Nitrogen Fertilisers and Inhibitors (Smart Fertilisers) have been developing next-generation ‘smart’ fertilisers for this purpose.
Native Australian soil microbes can safely break down some plastics
One focus we're exploring is the use of biodegradable plastic coatings (or bioplastics) to slow the release of fertiliser while minimising the environmental impact of the coating.
Environment
Smart fertilisers for food security
In a recently published study – a collaboration with industry partners, Incitec Pivot and Elders – with researchers from the Faculty of Science and the Faculty of Engineering and Information Technology tested several bioplastic candidates in a natural agricultural soil.
We studied the bioplastics under typical growing conditions to learn whether soil microbes could break them down into safe substances.
Previous research in this area has focused on other ecosystems (e.g. marine) or used purified laboratory microbe cultures or elevated conditions, like high temperature or boosted ultraviolet light.
Encouragingly, four of the seven plastic coatings we tested were degraded and ultimately converted to carbon dioxide and water under typical growing conditions by bacteria and fungi native to Australian agricultural soils.
There also appeared to be no negative effects of this degradation on the microbe populations.
Additionally, we identified the microbe species involved in the degradation to inform our design of bioplastic-coated fertilisers.
Some of the plastic-eating microbes provide the extra benefit of producing key plant nutrients, like phosphorus.
Other microbe species we found could also help tackle our burgeoning plastic waste crisis through the production of specific enzymes that can break down common plastics like PET – which could then be used in landfills.
Food from a healthy planet, for healthy people
Our next step is to test whether the four biodegradable plastics we found will enable efficient fertiliser delivery in glasshouse and field trials and assess their commercial viability.
A key challenge is to keep the cost of bioplastic-coated fertilisers competitive with market alternatives, to encourage their use by farmers.
Our research highlighted the importance of testing the ability of plastic degradation of the whole soil ecosystem, rather than focusing on individual microbe species.
The types and functions of microbes vary between different soils and can depend on each other or external factors like water availability.
So we need more research to determine how bioplastic fertiliser coatings degrade in diverse agricultural settings.
Another area for future research is the ability to tailor the thickness of the bioplastic coating to match the rate of fertiliser release to the growth pattern of key agricultural crops which would optimise their effectiveness.
By meeting these challenges, we aim to increase sustainable food production and ensure the health of our soils, plants, people and planet well into the future.
The research team was comprised of researchers from the Faculty of Science (Dr Zahra Islam, Dr Helen Hayden [formerly], Dr Elena Colombi [formerly], Associate Professor Hangwei Hu, Professor Deli Chen) and the Faculty of Engineering and Information Technology (Dr Pavel Cherepanov [formerly], Dr Wanjun Xu, Dr Omid Mazaheri, Dr Zhixing Lin and Professor Frank Caruso).