Spurred by convenience and burning restrictions, brush shredding takes off

By Vicky Boyd


A California-imposed ban on open-field burning of almond and walnut prunings may be five years away, but an increasing number of tree-nut growers are already turning to more environmentally friendly brush-disposal methods.

One that is catching on is shredding, where self-propelled heavy-duty machines pulverize prunings, turning them into matchstick-sized pieces of wood and depositing them on the orchard floor.

Eventually, the pieces decompose. Although shredding costs more, tree-nut growers who have used it say it’s more convenient, ridding an orchard of brush in a few days, rather than waiting weeks or even months for a day when they can legally burn.

“It’s a little more expensive than pushing the brush out, but you get it done all at once so you can get back to your routine,” says Gene Beach, a Merced-area almond grower and president of the Almond Hullers and Processors Association. “With a shredder, it’s so fast that they are essentially done in a very short time.”

Beach belongs to the Northern Merced Hullers Association, which purchased a shredding machine two years ago to service the cooperative’s members.

After the 2003 season, Beach had brush on about one-fourth of his acres shredded. The machine worked so well that Beach had brush on his entire acreage shredded after the 2004 season.

Growers have estimated pushing and burning costs $15 to $25 per acre, while having a custom shredder handle the brush costs $25 to $35 per acre.

Shredding on the rise

How many growers have adopted the practice is unknown, although representatives of the Almond Board of California say they know it’s growing annually.

Mike Flora, an engineer with Flory Industries in Salida, Calif., says he knows more growers have gone to shredding because of the increasing orders for Flory’s Pow’r Trak Shredder over the past two years.

With hammer mills, the 425-horsepower Flory machine pulverizes wood, turning it into toothpicks. Flora is quick to point out that there’s a difference between machines that chip and those that shred, like the Pow’r Trak. Chippers produce a larger product than shredders.

“With shredding, there’s more surface area, and it tends to break down better than a chip,” Flora says. Although the Flory rig weighs 27,000 pounds, the rubber tracks on which it travels allow it to work in wet orchards and minimize soil compaction.

A filled 500-gallon air blast sprayer can exert 12 to 15 pounds of pressure per square inch on its wheels.

The Flory shredder exerts only 7 psi, Flora says. “We have had operators who have run virtually through standing water in the orchard and shredded it,” he says.

If the prunings are stacked correctly, an operator of a Flory rig can shred 8 to 10 acres per hour. Some of the machines have covered as many as 6,000 acres each season. The ability to cover that kind of ground is a benefit of the rig, which has a $280,000 price tag, Flora says.

Where he has seen interest is from people with custom shredding businesses.

Quality is job #1

One concern nut handlers have had with chipping or shredding was with the residue left on the orchard floor and whether it will be picked up with the nuts during the following year’s harvest.

With growers using older chipping machines, Flora says those concerns may be warranted. But he says the new shredders, along with strides made in brush stacking and operator education, have greatly improved the quality of the job.

Timing of shredding also is a factor, Flora says. The sooner after harvest a grower can have it done, the longer the residue is exposed to rain and the environment, which aid decomposition.

In a Kern County trial where Flory representatives shredded brush shortly after the 2004 harvest,they couldn’t find any residue when they returned in February.

Despite the trial results, Flora says industry concerns about residue may be warranted in the southern part of the state. With less winter rainfall, the shredded material may not decompose quickly.

Shredders stand trial

University of California Cooperative Extension farm advisor Brent Holtz found that to be true in a trial he conducted in 2003 and 2004 in Madera County.

Based on initial surveys, Holtz says almond growers remove an average of 1,997 pounds of brush per acre annually from orchards. In the trial orchard, the grower considered it a light year and only removed about 1,247 pounds of brush per acre.

The trial involved four quarter-mile strips where trees received prunings and four quarter-mile strips that didn’t receive prunings. The prunings were then chipped.

Crews shook nuts the following year, allowing them to dry and then windrowed them. From 22-foot-long windrows, crews sorted and weighed the debris. They also sent five 10-pound samples to the U.S. Department of Agriculture for a federal-state inspection certificate.

In-shell samples from the chipped treatments averaged 0.755 percent wood compared to the non-chipped treatments, which averaged 0.0225 percent wood.

Holtz considers the difference “significant.”

Results look ‘promising’

Beach says the foreign material produced during chipping was a definite concern among hullers and shellers initially.

“With some of the early machines, there were a lot of sticks and brush that came in,” Beach says.

“With the newer ones, it’s still too early to tell the results, but it looks promising.”Dave Baker, Blue Diamond Growers director of member relations, agrees. “From what I see, the shredders have really advanced from what they had a half dozen years ago where they left fairly large chips out in the field. The problem really wasn’t at the handler level, it was at the sheller separating out the wood chips from the nuts.

“This stuff gets just shredded into almost nothing, and it breaks down really well, especially in the northern two-thirds of the state be-cause of the rainfall.”

One possible challenge may be with shredding in flood-irrigated orchards, Baker says. If the material isn’t totally decomposed before irrigation, it may float and pile up in areas around the orchard.But at least in walnuts, he hasn’t found that a problem.

Baker, who grows walnuts and flood irrigates, has had his brush shredded with a Flory machine and says it turns the wood to “sawdust.”

And it may not be a problem in almonds, if the shredding job is done correctly.

“In looking at almond shreddings, they are a little bit larger,” Baker says. “But I’ve watched my neighbor [who grows almonds] shred for two years now, and he has absolutely no problem at harvest at all. It’s a clean product coming back in.”