Compostable Sensors Could Help Grow Impact of Digital Agriculture

Screen-printed, biodegradable soil sensors that can be composted at the end of their lifecycle could enable farmers to improve crop yields while reducing electronic waste, researchers say.

The sensors, developed by engineers from the University of Glasgow in collaboration with colleagues from the Łukasiewicz Institute of Microelectronics and Photonic (IMiF) are made from electronic materials that degrade into plant nutrients, acting as fertilizer to help crops grow.

The research is a key development in a wider international project called TESLA, which stands for Transient Electronics for Sustainable ICT in DigitaL Agriculture. TESLA is led by the University of Glasgow and brings together partners from McGill University in Canada; Tampere University and VTT Technical Research Center of Finland Ltd in Finland; Łukasiewicz Research Network Institute of Microelectronics and Photonics in Poland and the CSEM Center Suisse d'Electronique et de Microtechnique SA in Switzerland.

The project aims to develop a complete system where the biodegradable sensors are powered by solar cells and supercapacitors also made from sustainable materials, enabling a fully environmentally friendly solution for precision agriculture monitoring.

The new technology aims to support global efforts to make food production more efficient and sustainable as populations grow and climate change presents new challenges for large-scale farming.

The biodegradable front-end sensors are paired with conventional electronics to monitor crop health. The team say their modular approach enhances the reusability of the overall existing electronic systems and significantly reduces electronic waste, resulting in a much lower overall environmental impact. Detailed environmental impact assessments conducted by the researchers show that operating the electronics in this way improves sustainability.

Their modular, hybrid electronics architecture has been applied to "digital agriculture," a new approach to farming that uses networked sensors directly applied to crops to monitor their environment and their growth. Digital agriculture could help meet the 70% increase in global demand for food that experts believe will be needed by 2050.

However, the current generation of sensors used in digital agriculture are made from non-recyclable materials. That means an expansion in the use of digital agriculture would also create an increase in environmentally harmful electronic waste when the devices reach the end of their lifecycles.

In their paper published in the journal ACS Applied Electronic Materials, the team describes how they made a digital agriculture sensor from sustainable materials, combining a biodegradable patch with a matchbook-sized reusable electronic module. The sensor patches are manufactured using a screen printing process, similar to that used in t-shirt printing. This low-cost, low-energy method of manufacturing could help enable the large-scale deployment necessary for the wider adoption of digital agriculture around the world.

In this work, conductive tracks are printed onto a biodegradable polymer substrate using graphene-carbon ink. Then, a sensing layer made from molybdenum disulfide is printed on top so all materials used naturally break down into plant nutrients.

Data from the sensors, which are sensitive to the changes in pH and temperature that can be caused by infections in crops, are collected by the electronic module. The data can be sent wirelessly to computers, which could in the future help farmers build up a detailed picture of the health of their crops.

Lab tests showed the sensors can reliably monitor soil pH levels, with consistent performance demonstrated in solutions ranging from pH 3 to pH 8 over the course of two weeks. The team also demonstrated that the sensors can detect traces of ethephon, a widely used plant growth regulator that can be toxic to humans and wildlife if it contaminates groundwater. At the end of their useful lifecycle, the sensors degrade into key primary and secondary nutrients to support future plant growth.

Dr. Joseph Cameron, of the University of Glasgow's James Watt School of Engineering, is a co-author of the paper. He said, "Reliable food production is one of the world's most pressing problems, with more than 800 million people around the world suffering from malnutrition today. Digital agriculture could be the key to maximizing our ability to produce enough food for a growing population."

Co-author Andrew Rollo, also of the James Watt School of Engineering, said, "The system we've developed could go a long way toward cutting down the carbon footprint of digital agriculture. The sensors themselves can be plowed back into the fields to help nurture crops, and the electronic modules with less environmentally friendly printed circuit materials can be reused for several years.