A sunflower seed falls, four cameras scan it, and a jet of air shoots it out of the stream. In Tiefenmühle’s colour sorter, it all takes milliseconds.
Marc Nyffenegger stands beside the three-storey dehulling plant. As the sunflower seeds pass down through it, they are first brushed to loosen the black hull from the creamy-white kernel. Then they are sieved. Finally, high-speed cameras inspect each kernel as it falls.
“If the system detects a variation in colour, a compressed-air nozzle shoots that particular piece out of the product stream within milliseconds,” says Marc Nyffenegger. Dark fragments of hull, mould-affected kernels, small stones, soil and plant debris are all removed.
Growing, processing and selling – on their own farm and in their own mill
Marlene Nyffenegger runs the 13-hectare farm that has been part of Tiefenmühle for generations.
Her husband Marc Nyffenegger processes their own harvest as well as crops from farmers across Switzerland. The couple sell some of the produce under the Alpenpionier brand.
This keeps the value added by processing Swiss organic cereals, pulses and oilseeds in the country – and in the business.
Bio Suisse has awarded its 2026 Grand Prix Bio Suisse to Marlene and Marc Nyffenegger’s Tiefenmühle in Herdern, in the canton of Thurgau, near Lake Constance.
The prize, worth 10,000 Swiss francs, is being awarded for the 20th time. It recognises innovative and sustainable projects in Switzerland’s organic sector. Previous winners are listed here.
“Tiefenmühle is an outstanding example of how gaps in agricultural processing can be filled, so that the value added from Swiss organic raw materials remains in Switzerland,” jury chair Madeleine Kaufmann said at a press conference.
The jury praised the couple’s courage and commitment. Tiefenmühle, it said, is far more than a farm mill: it is a processing platform for the entire organic sector, rooted in its region but with a reach across Switzerland.
A mill processing small batches for other farms
The plant dehulls and cleans crops and reduces microbial contamination. Harvests are delivered from across Switzerland, including:
Oilseeds: pumpkin seeds, linseed, hemp seeds and sunflower seeds
Pulses: lentils, lupins and field beans, also known as fava beans
Cereals: barley and millet
Only peanuts, cashews and hazelnuts are kept out of Tiefenmühle because of the allergens they contain.
For small farms, access to a mill that processes crops on their behalf can determine whether they can sell their harvest for human consumption at all. With such small quantities, a processing plant of their own would be underused. For Tiefenmühle, these orders provide work and income.