July 2004

Increasing Efficiency in Green Waste Reduction
Selecting the Right Chipper or Grinder for your Operation

Most logging operations face — probably routinely — the same issue: a need to get rid of “slash” and tree tops left behind after usable timber is harvested from a site. Some operations have the means to take care of this material themselves. Others hire contractors to do final cleanup or even complete land-clearing. Either way, someone needs the right equipment for the job, which typically translates into a large brush chipper, or a tub or horizontal grinder.

Chipper or grinder?
Two primary criteria are often crucial for clearing operations when making equipment selection decisions: mobility and productivity (and the first usually has a hand in the latter). But, the usual size of areas being cleared is a key consideration as well.

For example, if the land being cleared is most often limited to one to five acres, a large portable brush chipper is an option. And, assuming that the slash left behind would mostly involve smaller-diameter material (compared to usable timber) in this size range, these machines would be sufficient.

But, if the majority of jobs involve five acres or more, jumping up to a horizontal or tub grinder may be the best bet. One could assume that logging operations are most often harvesting land that falls into this category. In fact, most statistics show that logging involves 40 acres or more, even if it’s a selective harvest.

With respect to mobility, larger chippers are usually towed, which can be a challenge when trekking through narrow trails of a forest. In those cases, grinders equipped with tracks, which do not require a tow vehicle for movement around a jobsite, can be a distinct mobility advantage. Then come productivity considerations. Larger horizontal and tub grinders can range from 300 HP to 1000 HP and up. Obviously, they grind greater volumes of material, and they are faster than smaller machines. In addition, the size capacity of the units requires less handling of the branches, with horizontal models featuring 14 to 20 ft. feed tables.

One final consideration: some land-clearing operations sell the end material as a commodity product, such as mulch for landscaping. Mulch yards (buyers) sometimes require a uniform chip size. Larger grinders give you the ability to size the product while chippers usually do not.

Grinders for larger jobs
For many years, both types (tub grinders and horizontal grinders) have been successful in the market. Both excel in conditions and applications that match up with their capabilities. In short, tub grinders generally perform better with heavy, large-diameter material such as stumps and root balls. Certainly, a logging operation may leave behind unusable stumps. If stumps are the majority of cleanup, tubs are a good option. But, if processing longer raw material is the consistent application, a horizontal model may be the best choice.

There are other considerations though. Smaller loading equipment can be used for horizontal grinders, because they typically have a lower feeding height than a tub grinder. This could be a major factor, depending on the auxiliary equipment an operation has on-site.

These grinder “categories” sometimes come with options that are specific to each. In a situation where a single job site may have several debris piles —such as a land-clearing job, the self-propelled track-mounted option can be highly efficient. So rather than having to tow the machine short distances, it can be moved by the operator, possibly into areas where it could not be towed.

Among the primary advantages of having a grapple loader on your tub grinder is better visibility of the tub; the loader cab provides excellent view of the tub cavity, so operators can load material more efficiently. It also helps the operator identify and clear contaminants mixed in with material. Self-contained loaders may also eliminate the need for extra pieces of equipment, because transporting or renting a loading unit may not be required.

Non-loader machines are common on work sites that include a fleet of multi-purpose loading equipment. Some non-loader tub grinders require multiple auxiliary loaders to meet the production capabilities of the machine.

With so many options to consider, selecting the right equipment for land-clearing can be a challenge. But choice is a very good thing. Brush chippers, for example, have traditionally been used in tree-care applications. Now, larger models have made their way into the land-clearing market. Just a few years ago, tub grinders dominated the market for 400 HP and above. Since then, horizontal options are on the rise, and now tracked models are proving their worth among more and more processors.