Drying with warm air - Patrick Müller shows how it's done.
A Swiss dairy farmer has been drying his hay with a mobile biomass hot-air oven for three years.
Organic farmer Patrick Müller can use his grassland in the pre-Alpine hills in Switzerland five times a year. In the past, the hay on the farm was dried exclusively using cold ventilation. The farmer says: “Fans are power guzzlers. We had poorer quality dried fodder. Especially during the first cut in the second half of May, we always have a lot of mass and the weather is not yet ideal for cold ventilation.” In addition, the hay fans were mounted on the north side and the cold air sucked in only dried the hay slowly in spring and fall.
In spring 2016, the farmer opted for a warm air oven. He explains: “We drove to Pöndorf in Upper Austria with the trailer, looked at the system directly at LASCO and took it with us straight away.” The stove remained on the trailer, which the farmer had purchased especially for this purpose. He bolted the 1,850 kg burner to the trailer using angle irons, allowing him to move it at any time. The compact system only needs a 380 volt power connection.
He paid 42,000 Swiss francs (around 37,000 euros) net for the plug-in, fully automatic wood chip system with hot air hose and stove pipe. He was also offered alternative pellet stoves. He waves them away: “For me as a forest owner, wood chips are an ingenious solution.” Compared to the less expensive wood chip stoves, the farmer saves himself the trouble of having to frequently reload the logs with his system.
Müller prefers to mow in the afternoon with the conditioner and ted the same day. The next day, the farmer brings in the hay with 35 to 45 % residual moisture after tedding again. In spring, he lets the hay wilt for two days.
Depending on the weather, Müller needs 50 to 70 m3 of wood chips per year to dry up to 3,000 m3 of hay. The wood comes from his own forest. Depending on the quality of the wood, the kiln runs for up to 17 hours with one load. After each milking time, the farmer uses the telescopic loader to trickle two shovels of wood chips into the 2.5 m3 storage container of his 150 kWh system. The combustion chamber is continuously fed with fuel from below via an auger. This releases energy evenly.
From the burner, an insulated heating hose guides the 60°C warm air via three discharge pipes into the suction area, where the 15 kW fans are located. The fans push the warm air mixed with outside air from below into the two 500 m3 hay boxes, in which the hay is piled up to six meters high on a steel grid. To avoid losing too much heat, the farmer has insulated the floor from below. Since he has had the new system, he has ventilated it continuously until the hay only has a residual moisture content of less than 14%. “You can tell if the hay is dry when it no longer sticks to the hay tongs,” he explains. Müller’s hay now dries one to two days faster than with the fans alone. He saves electricity and is less dependent on the outside air. “We used to wait until the fodder under the roof was dry. Now I know that the drying is right,” he says with relief. Patrick Müller summarizes: “Our hay is now green, no longer brown. This has improved the cows’ appetite and there is also a little more milk.”
Text and photos: Karin CH. Taferner, Farmer Editor for customer magazine Heuwelt