When corn kernels (i.e. grain) are harvested, the corn cobs (the inner woody pith of the corn ears) are frequently discarded in the field. A Slovenian Operational Group investigated the potential of this valuable by-product as a renewable energy source on the farm. Working with farmers throughout the project, they developed a machine for harvesting both corn kernels and corn cobs, and tested various corn hybrids to identify the most suitable options for further use, such as energy production.

“Corn cobs are usually left on the field, mainly because people are not aware of their value. However, corn cobs have a lot of potential, so we wanted to find innovative, circular ways to add value to this by-product” says Mitja Krajnc from ŽIPO Lenart, the agricultural company which led the project. This project, which concluded in 2021, showcased practical solutions that farmers can implement to enhance energy self-sufficiency while reducing the cost of fuel for energy. By applying circular economy principles, this initiative opens pathways to environmental and financial sustainability for farms. The project also explored additional uses of the corn cob, including fuel, building insulation, animal bedding and feed, and as a raw material for the chemical industry.

The limited awareness of the potential uses of corn cobs has resulted in a scarcity of devices for the harvesting of this woody residue after corn grain harvesting. To address this gap, the project developed a technical solution for harvesting corn cobs and corn grain simultaneously. Computer models were made of two prototypes: a machine to collect the corn cobs as a single combine harvester (a combine harvester upgrade), and a machine similar to a tractor or harvester attachment. Because of the assessed efficiency, an upgraded harvester prototype was developed and tested during experimental harvests with different maize hybrids on five farms. Modifications were made to the harvester, including adding a storage tank for corn cobs to the outside of the machine. These changes made it possible to harvest the corn cobs without obstructing the harvesting of the kernels.

To optimise production, the project partners tested the cultivation of different corn hybrids. Twelve different maize hybrids were selected and sown on five experimental farms participating in the project. Cultivation methods were tested and adjusted, and post-harvest data was analysed, including yield per hectare, residue purity, hybrid-specific yields, and yield variations across farms. For each hybrid, the thermal characteristics, ash content, energy value, and other properties of the corn cobs were assessed. The partners also investigated other potential possible uses of these residues.

For participating farms which could not transform the corn residues on-site, a theoretical logistics plan was developed to transport the material from field to consumer. This ensured a steady supply of renewable energy sources, by-products, waste, residues, and other non-food raw materials for the purposes of the bioeconomy.

The project transferred the knowledge about harvesting corn cobs and their potential use to over eighty farms which were interested in testing the new method and boosting their incomes through greater energy self-sufficiency. This could also contribute to reducing the use of fossil fuels and reducing the negative impacts of greenhouse gas emissions. “Our project demonstrated the economic and environmental benefits of adopting renewable energy solutions. The agricultural businesses were empowered to thrive and be more resilient in a changing world” says Mitja Krajnc.