Orchard wood recycling offers disposal option


Issue Date: October 19, 2016
By Kevin Hecteman
A rototiller and spreader, were used to recycle wood chips from old orchard trees into the soil at a demonstration in Manteca.
Photo/Kevin Hecteman
Brent Holtz of University of California Cooperative Extension, is studying the benefits of such recycling.
Photo/Kevin Hecteman

Your old almond orchard has given upward of 25 years of faithful service. Time for those trees to retire. But the biomass plant down the road is closed—put out of business as contracts with utility companies expire—and burning the pile will get you in trouble with air regulators. Now what?

That conundrum got San Joaquin County farm advisor Brent Holtz to thinking some years back. What if, he thought, the wood chips from grinding up those trees could be recycled into the soil to enrich the dirt, push up the next generation of trees and eventually benefit the farmers?

University of California Cooperative Extension, where Holtz works, demonstrated another way to recycle wood chips into the soil for an audience of growers and dealers last week at Tallerico Farms in Manteca. The recycling project is being paid for by the Almond Board of California.

In February, UCCE held a demonstration in Chowchilla using an Iron Wolf machine. The most recent demonstration involved multiple machines, but held the promise of less expense and more coverage.

"The Iron Wolf is just one huge machine," Holtz said. "It's a 50-ton rock crusher that basically drives forward and grinds up the tree, and then it drives backward. It reduces its head into the ground. It acts like a big rototiller and incorporates the tree."

Holtz said researchers compared that process to the one demonstrated in Manteca last week.

"The Iron Wolf turned out to be slower than what we hoped," he said. "It could do about two acres a day. The process we demonstrated here can do 15 to 20 acres per day, but there are five different machines involved in the process."

The multi-machine process also appears less expensive, according to UCCE—it runs about $1,000 per acre, compared to about $1,500 an acre when using the Iron Wolf.

The machines include an excavator or backhoe to uproot the old trees; a front-end loader to transport the trees to the Morbark horizontal wood chipper; a spreader to distribute the chips on the orchard floor; and a rototiller to work the chips into the soil.

The demonstration in Manteca involved the spreader and rototiller, operated by Randy Fondse of G&F Agricultural Services of Ripon, which handled the chipping and spreading work for farm owner Louie Tallerico.

"We've been delivering the wood chips to biomass plants for years now, but there's been a shift lately into cheaper renewables like solar and wind," said Kelsey Nilsson of G&F. "We still do work with three, four biomass fuel plants consistently. We're just looking into another option for growers."

Nilsson described G&F as "initially apprehensive" about the multi-machine process, until Holtz described its potential benefits.

"With this, you can see the nice, even spread, which is a really big benefit in comparison with other options," she said.

Brothers Surgit, Kuldip and Sarabjit Atwal traveled to Manteca to see and learn for themselves. They grow almonds, peaches and pistachios in Tracy, Merced, Madera and in Kings County. They've previously sent their wood chips to a cogeneration plant, but that's getting to be a nonviable option.

"We'd like to pull my orchard, so we'd like to see how to broadcast this thing," Kuldip Atwal said. "It's a new thing for us. I said, 'Let's see that, where we save that material on my orchard.' For the nitrogen, all the nutrients, that's a benefit."

The brothers said they liked what they saw and intend to run with it.

We're going to have the benefits coming, I think, for many, many years," Sarabjit Atwal said. "We were grinding the peaches before—long time, last 20 years—(and these were) sent to the plant. Now, we like this new technology."

Holtz started his research in 2008 in Fresno, using an earlier Iron Wolf model to grind a stone-fruit orchard that was later replanted to almonds.

"I looked at the long-term benefits of adding all that organic matter to the soil versus pushing the trees and burning them," he said. "We had some very positive results from that trial. With a lot of cogeneration plants closing, there was interest to bring back this machine and look at how well it did in an almond orchard."

What if a retired orchard is plagued with pests or disease?

"Most of the pests or diseases are probably in the roots—nematodes or fungi living on the roots—and we really probably get very few roots out from the old orchard when we remove an old orchard anyway," Holtz said. "The woody biomass that we're incorporating now is probably the upper part of the tree that doesn't have a lot of fungi or nematodes growing on it."

Holtz added that scientists from UC Riverside and UC Davis are taking part in the trial to check for replant issues.

He said his previous research shows a cornucopia of positives.

"In the previous study where we ground the orchard, we saw a lot of benefits: soil nutrient levels increasing, most notably nitrogen and potassium," Holtz said. "We've also seen yield increases of as much as 200 meat-pounds per acre in the grind treatment versus the control, where we pushed and burned the trees. We think the economics of this process will pencil out."

(Kevin Hecteman is an assistant editor of Ag Alert. He may be contacted at khecteman@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.