Drying innovation provides increased energy independence for South Africa’s macadamia nut farmers as the country struggles to provide a reliable and affordable power supply.

Rising power costs and inconsistent supply brings a new set of challenges to the industry, requiring innovations in drying equipment. With this in mind, Adrian Padt, owner of the Durban-based engineering company Rocketworks, has designed a dryer that results in a 65% reduction in electricity.

With an ever expanding macadamia industry comes an increased burden on the national electricity grid to power up drying facilities to get the nuts to the optimum moisture level. With a doubling of production over the next 10 years, the demand for electricity is also expected to double.

Adrian Padt

Adrian Padt

And while the onus has traditionally been on processors to dry the nuts and erect the facilities required, farmers are increasingly being asked to deliver their nuts at least partially dried. “Burgeoning macadamia plantings around the globe has meant that processors and farmers have had to invest in expanded drying and storage capabilities on site, at significant infrastructure investment, and ongoing operating expenditure cost. Traditional solutions are expensive to build and run and are typically unaffordable for growers on the small to medium end of the spectrum,” Padt explained.

This led him to design a system that is not only cheaper, but also results in significant financial savings, increased quality and throughput, and which has an environmentally sustainable approach to the drying process of macadamias.

“DryMac is portable and can be stacked if there is limited space. It is notably more cost and time efficient than building a traditional bricks and mortar drying facility and by adding more units, it is designed to scale to a larger facility if required. An existing global network of spare parts is already available for most of the components of the container refrigeration units.”

The pilot test results demonstrate the potential to dry nuts at an average temperature of 28°C; between 4°C – 10°C° lower than traditional methods, which typically use electrical elements and large fans that are heavily reliant on electricity. Because the nut is exposed to lower temperatures during drying, the positive spin-off is a better quality of nut, which could be adversely affected when dried at temperatures that are too high.

The DryMac offers remote monitoring, alarming functions and control ability.

“We are really excited by the results of our on-farm trial of the DryMac,” said Padt. “It is a modern solution that for the first time combines refrigeration technology with heat pump drying, to create a unit that can both dry and store macadamias. This technology delivers superior output, including a more than 65% cost saving on electricity, depending on your current energy usage baseline.”

DryMac relies on the refrigeration aspect of its design to physically condense water removed from the nut, while simultaneously adding heat to promote the drying process. It is controlled automatically to an exact equilibrium to ensure all nuts are dried to the optimum level; as well as protecting them from over-drying.

Made from reefer containers, the DryMac is mobile and can be stacked

Using existing reefer containers, a globally adopted intermodal product (typically used to transport goods requiring temperature-controlled conditions), the DryMac is specifically manufactured to accommodate macadamias in bins.

“It is a simple ‘plug and play’ solution, with a straightforward installation process. Because it’s mobile, a farmer can transport the DryMac from farm to farm as required. When equipped, the DryMac offers remote monitoring, alarming functions and control ability. We have a database that will monitor and be able to offer drying and maintenance advice on each of our units,” Padt added.

The DryMac has a further benefit for farmers requiring longer term storage of their nuts as it combines refrigeration technology with heat pump drying, to create a unit that can both dry and store macadamias. The unit can switch to refrigerated storage for fruit and vegetables, or be configured to dry produce like mangoes. It could function in one way in the macadamia season, and another in the avocado season, for example.