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“With pentachlorophenol (penta) manufacturing ending in 2021, utilities are now looking for a replacement preservative for poles. Although a number of preservatives are available in the marketplace, most of them do not fit all the requirements and criteria of utilities,” according to Ken Laughlin, Divisional Vice President of Wood Preservation, Nisus Corporation.

Nisus Corporation is a service provider at the marcus evans Transmission & Distribution Summit 2020.

What is happening with penta and how will it impact the utilities?

Pentachlorophenol is used in the pressure treatment of utility poles, primarily in the western US because it is an oil-borne preservative which is needed for hard refractory species like Douglas fir that are difficult to treat. Unfortunately, it also contains dioxins which are a Persistent Organic Pollutant (POP) that has been problematic for some utilities that must monitor nearby water supplies for decades to come.

Now the supply of penta is in jeopardy. Penta was produced at a plant in Mexico that is being forced to close after Mexico signed on to the Stockholm Convention. The 152 signatory countries have pledged not to manufacture chemicals that are or contain POPs. Attempts to build a penta plant in the US have met strong resistance from the communities where they planned to locate, and the plans have been dropped.

With penta manufacturing ending in 2021, utilities are now looking for a replacement preservative.

What preservatives will be available for utility pole treatment in the future?

There are six preservatives available for use in poles: chromated copper arsenate (CCA), creosote, copper naphthenate (CuN, brand name QNAP), ammoniacal copper zinc arsenate (ACZA), dichloro octyl isothiazolinone (DCOI) and alkaline copper quaternary (ACQ).

CCA is the most popular preservative for poles and works well on soft wood like pine, but it is not as effective on hardwoods. DCOI has label issues that prevent it from being used at a concentration needed to meet AWPA standards. ACZA and ACQ are both corrosive and require stainless steel or similar bolts and fittings. Creosote (which is a probable human carcinogen) and QNAP are the remaining preservatives. With railroads shifting away from creosote, QNAP has become the fastest growing preservative for both railroads and utilities.

Douglas fir is a common species used for poles in the West. Can all available preservatives be used on Douglas fir?

Oil-borne preservatives like penta, creosote and QNAP are most effective at treating hard refractory species. With the demise of penta and a choice between QNAP or creosote, more utilities are choosing copper naphthenate due to longer service life and the fact that it contains no carcinogens, no dioxins and no POP.

How does Nisus add value for utilities?

Nisus provides a depth of knowledge to utilities in several important areas including access to PhD-level scientists in the areas of wood preservation, mycology, microbiology and entomology. All are leading experts in their fields who continually research and publish in their respective fields. Much of this research is conducted in cooperation with major universities around the country and the world. We also provide expertise in the area of treatment plants, as our VP of the Wood Preservation Division was previously president of a USD 60 million/year treatment plant. Finally, our regulatory department works closely with federal, state and local agencies and can help keep utilities stay abreast of pending regulations that may impact them.