Andrew Fisher, Mark White and Zelmari Coetzee*

The Agriculture Victoria team at the Mildura SmartFarm, in collaboration with Harveston Aeration Solutions and under the guidance of Dr Zelmari Coetzee, have successfully demonstrated the drying of wet almonds using ambient aeration.

In late 2023, the University of South Australia's Professor John Fielke suggested to the team at Harveston Aeration Solutions that the almond industry had a drying and storage problem that could be solved with ambient aeration.

Professor Fielke pointed to previous industry levee-sponsored research (AL12003 Advanced processing of almonds) that concluded aeration was a valid method for reducing moisture in harvested almonds.

Figure 1: Ambient air-drying curve for the whole fruit, hull and shell from Day 0 to Day 23.

The Harveston team devised a solution by combining their product storage and aeration knowledge with this almond-specific research. The completed product is a hybrid solution between a silo and current stockpile bunkers, coupled with an integrated aeration system and a smart controller. The entire solution is dedicated to the drying, storage and fumigation of almonds on-farm until delivery for processing.

"The system had to be easy to erect and be capable of meeting industry needs for controlling moisture, mould, insects, and vermin. I am very proud of our team's work and the solution they devised,” Harveston’s founder, Andrew Fisher said.

Dr Coetzee from the Agriculture Victoria Mildura Smart Farm was approached to assist in evaluating the solution. The collaboration with Harveston began, and the project was funded by the AgTech Regional Innovation Network (AgRIN) and Agriculture Victoria Research (AVR).

This type of demonstration is part of the primary purpose for the SmartFarm as the Mildura SmartFarm experimental almond orchard is a platform for research and innovation into the management of current and the design of next generation planting systems and the evaluation of novel agtech.

Figure 2: Ambient air conditions during the drying phase from Day 0 to Day 23. 

Three aerated storage rings were constructed at the Mildura SmartFarm – the ring sizes were determined to accommodate for the yield of the 11ha of plantings. Sourcing suitable harvested fruit for the demonstration proved problematic as weather conditions had significantly delayed the SmartFarm harvest.

Fortunately, a local producer diverted 20 tonnes of wet field weight of shake-and-catch harvested 'Wood Colony' with a high percentage of leaf trash, and the demonstration commenced. The product was at the upper end of moisture expectations, and despite being very late in the season, the desired results were achieved.

To ensure rigour in the demonstration, Dr Coetzee deployed a sensor array from Incyt to map the conditions inside the stockpile in detail. Scientific methods for sampling and measuring moisture levels across the fruit, hull, shell and kernel were implemented for the project. The results are shown in figure one.

When analysing the results, we can see a steady decline in moisture levels within the stack. We can also see where an evaluation of fan run speed was undertaken post-day 17, where the drying rate slowed.

"We had the best of the worst conditions for this demonstration," Harveston engineer and PhD candidate Mark White said.

"We had three rain days, six frost days and many days where the relative humidity fell into the upper levels of the range required.

“This drastically reduced the number of fan run hours on those days. Yet we still achieved the desired result."

Figure two shows the ambient conditions during the drying phase demonstration.

At the end of the drying phase, the industry-standard moisture requirements (AlmondCo 2023 crop delivery information) of six per cent kernel, 12 per cent hull and nine per cent fruit were achieved without loss of quality. The total energy cost for the drying phase was $69 or 1.3 cents per kernel kilogram.

Further evaluations were conducted in the maintenance phase of the project, including airflow modification and fumigation effectiveness. The results of these evaluations will be published when available.

In all, the team was very happy to demonstrate the effectiveness of ambient aeration and to add to the success of the Mildura SmartFarm.

*Andrew Fisher is director of Harveston Aeration Solutions, Mark White is a PhD candidate at the University of South Australia and engineer at Harveston, and Zelmari Coetzee is a researcher at Agriculture Victoria’s Mildura SmartFarm.