By Johan Coetsee
Cleaning canola seed – removing husks, stalks and other debris – can be a slow, labour-intensive task. That’s why farmer Attie du Toit from Nooitgedacht near Bredasdorp built his own device that allows one person to clean up to a tonne of canola seed per day.
Attie saves canola seed from his harvest mainly to sow as grazing for his livestock. The challenge is that freshly harvested seed is mixed with things like husks and stalks, and needs to be cleaned before planting, or it risks clogging the planter and affecting seed flow.
“Cleaning it by hand is incredibly time-consuming,” Attie says.
Small-scale mechanical seed cleaners are not available on the local market. Attie, who is a problem-solver, knew there had to be an easier way than to sort the canola seed by hand. “Like everyone these days, I turned to Google and YouTube. That’s where I found the idea of using air movement – specifically suction – to separate the heavier canola seeds from the lighter husks and other debris. The key component is an ordinary household vacuum cleaner.”
Using this idea, he designed and built his own “seed-vac”, a simple, clever invention that uses airflow to make seed cleaning faster, easier and more efficient.
The first step was to build a simple wooden frame out of plain pine, measuring 44 cm wide by 58 cm high. He fitted a sheet of transparent Perspex to the front, and a solid pine board to the back.
At the top left of the box is an inlet hole, into which a large plastic funnel is inserted. This is where the uncleaned canola seed is poured in. Inside the box, directly beneath the funnel, are two internal channels: one runs straight down, while the other branches off to the right.
The vertical channel contains several small triangular wooden pieces fixed along the sides – almost like barbs – designed to deflect and slow the seed as it drops through. The side channel, which connects to the vertical one, is formed by two longer planks and leads to the bottom right of the box, where debris is collected.
Here’s how it works
Attie explains that the unclean canola seed is poured into the funnel at the top of the box. On the opposite side, near the top, there’s another hole that fits the nozzle of the vacuum cleaner snugly. When the vacuum cleaner is switched on, it creates a strong suction that creates a vacuum inside the box. As the seeds enter through the funnel, they bounce around in the airflow.
The heavier, healthy canola seeds are less affected by the suction. They drop straight down through the vertical channel, passing between the triangular wooden “barbs”, and fall into a plastic bucket placed beneath an opening at the bottom.
The lighter material – such as seed hulls, small sticks, dust and other impurities – is far more responsive to the airflow. These bits swirl around inside the vacuum chamber and are quickly drawn towards the side channel, where the vacuum hose creates the strongest suction. From there, the waste is carried downward and collected for disposal.
Some of the husks and things that initially escape suction may swirl partway down the vertical shaft. Because they’re so light, the airflow pulls them back upwards, causing them to bounce off the wooden “barbs” and eventually exit through the debris outlet.
“It’s a simple but highly effective concept for quickly cleaning dirty canola seed,” Attie says. “I’ve found that the seed collected in the bucket is about 98% clean. Another big advantage is that one person can clean up to 1 tonne of seed per day, just by feeding it into the funnel and emptying the bucket of clean seed.”
The cost to build it was minimal. “I spent about R185 on the Perspex and thin-sawn pine, and we used an old household vacuum cleaner we already had.”
Attie notes that no small-scale seed-cleaning device like this is currently sold locally – and for his needs, it’s ideal. Large commercial seed-cleaning machines are available, but they are prohibitively expensive.
In 2024, Attie’s seed-vac earned him a prize in the Farmers’ Plans Competition, run by Landbouweekblad, Omnia and Grain SA at Nampo Cape, in the Machinery, Implements and Agricultural Equipment category.
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