Wood waste recyclers: how to decide which high-volume grinder is right for you.

Arbor Age; 5/1/2006; Peterson, P.D



It has allowed many tree care professionals to complete a cleanup job quickly and efficiently. Still, there are situations in which the wood chipper is not the best tool for the job at hand.

Perhaps you are clearing a large lot, with several large root balls and other woody debris to dispose of when the job is done. Or perhaps there is a large amount of hardwood on the site and it seems a shame to just chip it up and haul it away--and pay a tipping fee for the privilege. Either of these scenarios is a perfect situation for using either a tub grinder or horizontal grinder to reduce the wood debris into useable (and profitable) mulch.

Tub and horizontal grinders use a hammermill to reduce wood (and other products, depending on how you spec the machine) into uniform particles. Some companies even offer a coloring unit so you can produce colored mulch.

Of course, these machines have differing characteristics, which should be taken unto account before you decide on which machine is best for you.

Tub grinders

Tub grinders are loaded from the top into a tub. Tub grinders are generally equipped with a loader, so no other piece of equipment is needed to feed the machine. They are available with hydraulic tub tilt, which makes service and unloading easy. And tub grinders are very productive; once the tub is loaded, it will happily chew away until the material is gone--making it ideal for large sites. Tubs can digest large objects, roots, stumps, etc., very well.

Tubs have changed over the years, with manufacturers offering hydraulic and "soft" couplers between the grinder and the power plant to reduce the likelihood of damage caused by a sudden stoppage, and debris guards to reduce the amount of expelled material.

Horizontal grinders

Horizontal grinders, as the name implies, are parallel to the ground, and are fed by a conveyor onto which the material to be ground is placed.

One advantage of horizontal grinders is portability; many of them are on tracks and can be driven about the job site. They are also easy to set up and take down.

Since they are conveyer fed, horizontal grinders tend to do better with long, stringy material than tubs, and they enjoy less flying debris due to their orientation. If you are working in a neighborhood or urban environment, a horizontal grinder is an excellent choice. But again, manufacturers are making both types for a reason, depending on what you are doing.

Things They Should Both Have

Whether you are looking at a horizontal or tub grinder, you are going to be spending several thousand, in some cases more than one hundred thousand, dollars for a quality grinder. Given the level of money you will be spending, you owe it to yourself to do the research and make sure the purchase is one with which you will be happy.

Make sure that the company you are considering doing business with has the service personnel and resources to keep your machine running once it leaves the factory. Ask about their parts inventories, service turnaround time and warranty information. Ask other contractors who are grinding what they like or don't like about the service they are getting.

Also, try calling the parts department and ask for several parts for the machine you are considering. They should always have common wear parts in stock, and they should have a quick turnaround time on items they don't have.

The type of sales force a company has also says a lot about the way you will be treated later. A good salesperson is interested in making sure you are getting the machine you need. They will take the time to answer all your questions, and ask a few questions of their own so they can properly match you with the right piece of equipment.

Look over the machine closely. Does it have plenty of safety features? Are the controls easy to understand and labeled well? Service is something you will be doing some of in the field, so how easy is it to get to routine wear items? Is the machine equipped with a power train protection device of some kind, and, if so, is it easily repairable if it fails?

Finally, make sure you are buying a large enough machine to do the type of grinding you will be doing this year, next year, and beyond. Grinders are a long-term investment, so make sure you get one that will handle the growth of your business as well as it handles debris.

P.D. Peterson has been associated with the outdoor power industry for more than 15 years, as a technician, service manager and writer. He is an expert in the field of outdoor power equipment. He may be reached at