Simple Steps to Reduce Dust at Harvest

By Marni Katz

Special to California Almonds

July/Aug. 2007

Almond growers in the San Joaquin Valley continue to face pressure from air quality regulators and the public to reduce dust emissions from their harvesting operation. The Almond Board of California for the past four years has been supporting research to help better understand and reduce PM10 dust emissions at harvest.

The Valley has been narrowly in compliance with federal PM10 standards in recent years, but growers still need to pay attention to dust and find ways to further reduce their emissions at harvest.

A careful look at the different stages of almond harvest by Flocchini and Cassel at UC-Davis reveals that pick-up at harvesting emits the most dust, followed by sweeping and then shaking. Pickup machines typically emit four times more dust than sweeping, which is about 10 times dustier than shaking. Research efforts, as a result, have focused more on reducing PM10 and other dust emissions from pickup harvesting and sweeping. Downey & Giles at UC-Davis have measured relative amounts of dust from sweepers and pick-up machines with various set ups.

Here are some steps growers can take to reduce harvest dust, particularly in sweeping and harvest pick-up operations:

• Set Sweeper Heads to Optimum Level Per Manufacturers Recommendation. Research shows that sweeper heads set a half-inch below optimum levels substantially increased the dust released by the sweepers through contact with the soil surface. Heads set too low can also nearly double the dust released by the harvester.
• Reduce Blower Passes Where Possible. Making three blower passes doubled the amount of dust released from the orchard during harvest, compared to making a single blower pass.
• Use Wire on Sweeper Heads Instead of Rubber. Sweepers with rubber tines significantly reduce dust emitted compared to those with rubber sweeper head parts.
• Reduce Pickup Machine Speed. Slower pickup speeds of 1.5 mph cut dust emissions by 50 percent compared to speeds of 3 mph.
• Lower Separator Fan Speed. To the extent possible, reduce separator fan speeds to
• Maintain a clean orchard floor. In almost all these cases, a well prepared orchard floor prior to harvest will reduce dust produced and provide an orchard more conducive to each of the previous mentioned steps.

Gabriele Ludwig, Senior Manager, Global Technical & Regulatory Affairs with the Almond Board of California, pointed out that orchard canopies often act as filters for dust and emissions are more likely at the ends of rows during turnarounds and near the edges of orchards.  Thus, special care should be taken in those areas – similar to spray-drift. Research is continuing on other possible measures including understanding all the options for the edges of the orchards.

She also notes that paying attention to dust emissions in harvest not only helps promote good air quality but can also impact food safety.

“If you can reduce your dust you reduce the chances if there is a pathogen in your orchard, of moving it around as much. So we need to be paying attention to do not only to help keep the San Joaquin Valley in compliance but also to help promote good food safety strategies.”

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