Answer Man: Stump dump grinding machines cost how much? Duke Energy ‘rider adjustments’ bill confusion?

Today’s round of questions, my smart-aleck replies and the real answers:

Question: I was recently driving down Riverside Drive where there is a very large mulch yard. The machine that grinds up the piles of brush, timber, and large stumps was running at full capacity. It’s a pretty amazing process to watch. What does a machine like that cost? And what are its specifications? How long before a unit like that has to be replaced because of the incredible demand on its working parts? Where are these machines made?

My answer: What is it about stump grinding, log splitting, and tree felling that is so daggone mesmerizing? I once watched a video for at least 10 minutes of some kind of mammoth grinding machine obliterating a large pine tree from the top down. As a guy who generally really likes trees, I’m not proud of this.

Real answer: This is the Riverside Stump Dump operation, and when I stopped by last week, Martin Barnwell gave me a fascinating tour of the place. And yes, one of the grinding machines was chewing up wood and spitting it into a huge pile.

The company has five grinders of varying sizes, and the one in operation on this day was a smaller model. When grinding wood waste, it can spit out 250 cubic yards of material an hour, said Barnwell, the operations scheduling coordinator.

To put that in perspective, the biggest dump truck Riverside operates can handle about 30 yards of material. Riverside also utilizes some tractor-trailers built for hauling wood grindings, and they haul about 75 to 80 cubic yards each.

When Riverside gets good logs in, they’ll go to a sawmill, Barnwell said. But a lot of material is what they call wood waste, which can include tree tops, limbs, hedges, and other material.

That primarily goes to a biomass plant in Georgia that burns it to produce power, or to a company in Kingsport, Tennessee, called Domtar that makes recycled containerboard. Barnwell said Domtar burns the wood waste the stump dump sells to generate power.

Riverside Stump Dump also used to sell the same material to the now-closed Pactiv Evergreen paper plant in Canton, which also used it for power generation, Barnwell said. In the industry, this material is known as “hog fuel” or “boiler fuel.”

This material is ground up just once through the machinery, but Riverside is known for its huge piles of mulch, which typically come from hardwood trees that are ground up twice.

“The double-ground mulch is like what you’d get at Lowe’s or Home Depot,” Barnwell said. “We also have a black mulch that ages naturally and turns black. We don’t use any dyes or chemicals.”

The company does sell single grind mulch for $22 a cubic yard. It’s the same material that goes to mills for boiler fuel, but when it’s used as mulch the most common uses are for dog lots, walking trails, or areas where ground cover is needed.

Riverside sells double-ground mulch for $25 per cubic yard and the aged, dark stuff for $28. IT also sells hardwood bark, screened topsoil and a pine bark product, which are more expensive.

The stump dump also makes money by charging folks to dump stumps and other materials. It does not accept treated or painted wood, plywood, particle board, or creosote-treated wood. Riverside does grind up pallets, and it had a huge pile of them awaiting the grinder on my visit.

You may wonder about the nails in pallets, as I did. The grinding machines have a powerful magnet on the end of the conveyor belt to snatch out the nails, which are then sold to Biltmore Iron & Metal Co. recyclers as scrap metal.

The pallet grinding material goes strictly to the mills, Barnwell said. They actually pay more for that, as it’s drier and burns better.

Now, about those grinders. While they do have a lot of parts, they’re pretty simple machines. They have a trough and a conveyor belt to accept the material, which hits a spiked drum first and then proceeds to the internal grinding drum, which is driven by a diesel engine that can generate from 900 to 1,100 horsepower, depending on the machine. Then another conveyor spits the ground material onto the pile.

The metal teeth that do the grinding are hardened steel with embedded carbide. They’re shaped like a small brick and about the size of your hand. The company’s smaller grinder, which weighs about 80,000 pounds, has 28 of these teeth.

Three of the machines Riverside cost more than $1 million each, with a couple hitting the $1.2-$1.3 million range. The other two are older, from the late 1990s, so pricing them in today’s market is tough.

Riverside buys its machinery, instead of leasing, and Barnwell says the grinders typically last about 10 years. Riverside also has the ability to laser cut steel to make some parts on site, and it’s constantly maintaining its equipment.

Besides the grinders, Riverside has five trackhoes, five over-the-road semis, two dump trucks and two front loaders. Those front loaders are huge, too, and run about $500,000 apiece.

Here’s a cool little factoid: The grinders are remote-control operated, so the trackhoe operator who’s loading them actually controls the grinder as well. The biggest grinder they have could chew up a 24-inch diameter log.

Riverside can transport its grinders for on-site grinding.

The business dates to the early 1980s, and the owners are Ronnie and Clara Ray. It’s open to the public, but as you can probably guess by those huge mountains of mulch, the company also serves landscapers, and it sells to the large plants.

Barnwell said spring and fall are the busiest seasons, and Riverside can see 50 trucks a day coming in to drop off or load up. Riverside, located at 620 Riverside Drive, also has a location in Mills River.

While some people have complained about the business, as it covers about four acres and generates a lot of truck activity, not to mention wood dust, Barnwell points out its main benefit.

“If it goes to the landfill, it gets buried,” Barnwell said. “We call ourselves a wood waste recycler.”

Riverside Stump Dump has 17 employees between its two locations.

Question: I noticed a new item on my Duke Energy bill, “summary of rider adjustments.” In my case, it was an increase of $7 over previous bills, but a call to Duke suggests it will be higher in the future. What is this? Is it just another “junk fee” that is becoming ubiquitous? The bill states my rate is about 12 cents per kilowatt hour, but after fees, riders and taxes, it’s actually over 16 cents.

My answer: If I were paying this fee to watch stump grinding videos, I’d be OK with that.

Real answer: Duke Energy spokesperson Keith Richardson said the “summary of rider adjustments” on the bills now covers additional costs Duke Energy is allowed to recoup. Also, they’re not new.

“Prior bills showed these costs, which customers have always paid, as part of the base rate on the bill,” Richardson said via email. “The new bills list these costs separately from the base rate.”

Richardson also noted some “fluidity” exists in the rider amounts “because of necessary and frequent adjustments due to circumstances like an increase in fuel costs.”

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