At one time, you used to be able to burn any wood waste created on a jobsite. When that was no longer acceptable, you buried it in a landfill. But today, landfill space is in short supply. Higher disposal fees and tighter restrictions make it increasingly expensive and difficult to simply haul away tree stumps, logs and branches for burial at the dump.
"The EPA and several state governments are pushing to keep all organic material out of landfills," explains Mike Byram, senior director for the environmental business segment at Vermeer."Limiting the amount of wood waste that can be buried in a landfill is one of the quickest and easiest ways for them to meet their diversion rates."
Because of the changing attitude toward wood waste, contractors are relying more heavily on wood grinders as solutions to their disposal dilemma. Some simply want to reduce the amount of bulk they take to the landfill. Others are turning lemons into lemonade by creating value-added end products such as mulch, fuel and compost.
"More and more, we're seeing that it isn't just about turning big chunks of wood into little chips to send to the landfill," says Byram. "Now contractors are trying to find ways to make something they can sell. We've seen a huge increase in the United States for colored mulch, which can sell for as much as two to two and a half times more than mulch that isn't colored. And it doesn’t cost a contractor that much to add the color."
Match to material size and shape
Whatever your intent, selecting the right grinder for the job is important. The one that’s right for you boils down to personal preference and an evaluation of the application.
Wood grinders fall into one of two categories: tub or horizontal grinders. Both contain some type of hammer mill (fixed, upswing, downswing, etc.) where all the grinding takes place. And both contain screens with grates that determine the size of the end product. But that’s where the similarities end.
"With a horizontal grinder, you feed the material horizontally from the side," he continues. "A hydraulically driven feed system turns and crushes the material and brings it into the mill. You have more control of the feeding of the material, and you can back that material out if you need to."
While each type of grinder can be used on a jobsite to reduce wood and wood products, each has its specialty. Because of its large opening, a tub grinder is most efficient at chewing away at bulky items such as tree stumps and large root balls. Material length is based on the depth of the tub, notes Byram.
"We have one grinder with a 13-ft.-diameter tub," says Brandon."You can put as big a stump as will fit in that opening."
Conversely, most horizontal grinders can only accept material up to about half that diameter. However, when it comes to grinding long lengths of material, such as trees that are 40-, 50-, even 60-ft. tall or more, a horizontal grinder will be more efficient because you won’t have to spend extra time cutting the log into shorter lengths.
"With a horizontal grinder, there are no length restrictions," says Brandon. "Once you get the butt end of the tree started through, it keeps grinding until the log is gone."
Jobsite factors to consider
A horizontal grinder is also better suited to more congested work areas, explains Bill Gehoski, regional sales manager at Bandit."Some tub grinders can throw debris 1,000 ft. or more into the air," he says."There are certain areas, such as the city of Tampa Bay, where you can’t even use a tub grinder. But a horizontal grinder can work in these areas, as well as alongside roads, etc."
It is also important to adhere to the thrown object safety zone when using a tub grinder."Don’t use a tub grinder next to a highway or in a shopping center or subdivision where you can’t control the traffic around it," says Brandon. "Instead, use a horizontal grinder because it contains the debris much better. Once the material is in the grinder, it seldom is ejected."