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The low-dust E8000 self-propelled harvester from Exact Corp. of Modesto uses a water mist and brushes to scrub dust from the air, depositing it on the orchard floor. Photo by Vicky Boyd.

By Vicky Boyd

As the acres of almonds have grown in the state, so, too, have the number of dust complaints lodged by the general public.  "Just yesterday, I got a call from someone in Modesto who was basically griping about the air quality and the dust," said Gabriele Ludwig, Almond Board of California's director for sustainability and environmental affairs. "She said she couldn't breathe. 

"As the industry has grown, the dust that's always been there has become more noticeable to the residents of the Central Valley."

In response, the Modesto-based Almond Board has already developed a set of best practices growers can follow to minimize dust during harvest. Among those are starting with a clean orchard, properly adjusting equipment, using slower ground speeds and slower fan speeds with older harvesters, and planning your route so you don't blow into roads.

The Almond Board also recently held two side-by-side demonstrations of four low-dust harvesters so growers in different parts of the state could gauge for themselves the different technologies. 

The Van Duyns, who hosted a similar event last year in one of their Escalon orchards, did so again this year for Northern California producers.

But instead of the three machines put to the test in 2016, four manufacturers brought equipment this year. They were Exact Corp. of Modesto, Flory Industries of Salida, Jackrabbit Equipment of Ripon and Weiss McNair Nut Harvesting Equipment of Chico.

The Exact E7000 and Flory's 8700 were self-propelled harvesters whereas Jackrabbit's Harvester and Weiss McNair's 9800 California Special were tractor-drawn PTO units.

Each machine reduces dust using slightly different technology.

Getting a first-hand look

Lucas Van Duyn said his family hosted the event both years so they could get a closer look at how the machines performed under their own conditions. At the same time, they wanted to allow fellow growers to see.

Nick Gatzman, a pest control adviser with Travaille & Phippen Inc. in Manteca, was one of about 100 people who came out for the demonstration.

"I just wanted to see all of the differences between all of the low-dust machines," Gatzman said. "If there's a low-dust machine that works well, that's something we may want to move to to help with the dust issues. We have to do what we can do."

The Van Duyns already pay close attention to dust during harvest, trying to minimize it if possible. 

"It's tough," Lucas said. "You can set your head the best you can, but there's still a lot of sand that gets collected."

Reducing dust is easier in orchards with heavier soils than in ones with a lot of sand, such as the one where the demonstration was held, said Lucas' father, Steve Van Duyn.

"We got to see how good they are at taking the dust out," Steve said. "What they also need to do is build speed into the machines for when there are rain clouds in the sky and you need to get done."

On the heavier ground with naturally less dust, Steve said harvesters can run 4 to 4.5 mph without creating big plumes. But conventional machines may have to slow by up to 50 percent on the dustiest ground, which in turn slows the entire operation.

A scientific examination

Studies conducted by Texas A&M in 2010 and 2011 compared PTO-driven low-dust machines from Exact, Flory and Weiss McNair to a conventional harvester. Because each harvester was tested on a separate day when weather conditions could be different, the study's author, Texas A&M agricultural engineer William Faulkner, warned about making comparisons among machines.

The Exact E4000 produced 76 percent fewer total suspended particulate emissions and 72 percent fewer PM 10 emissions than the conventional harvester.

Flory's 8550 reduced total dust by 41 percent and reduced PM 10 emissions by 35 percent compared to the conventional harvester. And the Weiss McNair 9800 California Special reduced total particulate emissions by 26 percent and PM 10 emissions by 45 percent compared to the conventional machine.

Jackrabbit's harvester was not included because it had not yet been introduced to the market. Ludwig said she hoped a similar study will be conducted on that machine in the near future.

How many of the low-dust harvesters are being used commercially by California almond growers and custom harvesters is unknown, Ludwig said. The Almond Board currently is drafting a survey to try to get a handle on the numbers.

Stuart Layman of Flory Industries said he's seen a small uptick in interest in low-dust machines. A low-dust version of a PTO harvester will cost about $15,000 to $30,000 more than a comparable conventional machine, Layman said. Flory only sells self-propelled units with the low-dust technology. 

What potential buyers are typically more interested is a machine's efficiency and how many acres it can handle in a day, he said. "It's more about the capacity of the machine – that's what people are going after and is it faster than older machines?" Layman said. Flory first introduced a low-dust harvester in 2002.

Jason Bayer, a salesman for Exact, said he's seen growing interest in the company's self-propelled and PTO low-dust harvesters. "It's increasing – absolutely," he said.

The company introduced its first low-dust PTO model in 2006 and a self-propelled version about two years ago. 

For growers interested in buying or using low-dust harvesters, the Natural Resources Conservation Service has cost-share through its Environmental Quality Incentive Program, or EQIP, said Grace Gomez, a NRCS soil conservation technician in Modesto.

Participants are required to sign a four-year contract. During each of the first three years, they will receive $36 per acre of almonds on which one of the three university-tested low-dust harvesting technologies is used. Growers who have orchards custom harvested using a low-dust machine also could qualify.

During the contract's fourth year, the signer will not receive cost-share. In addition, participants must have had their orchards harvested using older, conventional machines for at least one year.

Why the dustup?

The almond industry has cause for concern since it is the largest producer of PM 10s – dust particles 10 microns diameter or smaller – of any agricultural commodity in the state. By comparison, a human hair is about 100 microns.

Almond harvest, which involves picking up windrowed almonds from the orchard floor, produces about 41 pounds of PM 10s per acre per pass, according to Air Resources Board figures. That compares to the next closest crops with 5.8 pounds of PM 10s per acre for wheat harvest and 3.4 pounds per acre for cotton harvest.

Broken down for almond harvest, nut harvest or pick-up accounts for about 90 percent of dust production, and the remaining 10 percent comes from shaking and sweeping, according to Texas A&M University studies.

PM 10s have come under scrutiny by regulatory agencies because they can be inhaled deep into the lungs, causing respiratory problems. In addition to agriculture, PM 10s are produced by a number of other sources, including motor vehicles, wood-burning stoves and fireplaces, wildfires and waste burning, and industrial sources.