Southern Exposure: Long-Term Field Testing of Wood Protectants

When researchers are looking to evaluate the performance of wood protectants, the harsher the environment the better. Which is why Forest Products Laboratory (FPL) researchers put specimens to the test in the Harrison Experimental Forest (HEF) in Saucier, Mississippi, and have been doing so for 80 years.

Generations of FPL researchers have used the HEF field site for sub-tropical field testing. Here Oscar Blew is rating posts at the HEF (1950’s).

Located about 35 miles north of the Gulf of Mexico, this sub-tropical field site receives about 60 inches of rainfall a year and has a mean temperature of 68 degrees Fahrenheit. The wood decay hazard in this area is rated “severe” according to the American Wood Protection Association Use Class Rating System and there is significant subterranean termite activity. When in ground contact, untreated wood rarely lasts 12 months in the HEF, to which researchers respond “challenge accepted.” Continue reading

Meet the Researchers: FPL Scientists Featured in Crossties Magazine

The Railway Tie Association publishes a magazine, Crossties, for producers and users of treated wood crossties and related products. The May/June 2017 issue introduces a new regular feature called “Meet the Researchers,” and it kicks off by showcasing researchers from the Forest Products Laboratory (FPL).

This makes perfect sense, as one of the original goals for early FPL scientists was developing preservatives for railroad ties. More durable rail ties lengthened the service life of ties in use, and helped ease the demand for lumber, as trees were being cut at alarming rates across many northern and western forests.

Over time, lumber treatment and preservation research focused on environmental concerns as well as durability. Today, FPL researchers in the Durability and Wood Protection group continue to work on improving the treatment of wood.

You can read the full issue of Crossties here. See page 13 for the Meet the Researchers feature.

Time in a Bottle: Finding New Life for an Old (Yet Reliable) Test Method

The simple soil bottle presents an extremely useful tool for predicting performance of preservative treated, modified or naturally durable woods. The methodology was developed in the 1940s exclusively for evaluating wood preservatives against wood decay fungi. It has been adapted over several decades to include naturally durable woods, wood plastic composites, and engineered wood products, and we use it constantly here at the Forest Products Laboratory (FPL).

The basic premise of the soil bottle is a material is presented to an actively growing fungus in an otherwise sterile environment. The resistance of the material to fungal degradation is determined by comparison to reference materials (non-durable species or treated reference material). The soil bottle also presents an excellent tool for studying basic fungal biology whereby cellular changes in wood during the decomposition process can be analyzed.  The soil presents a refuge for the decay fungus as well as a source for moisture and transported ions relevant to the decay process.

Past, present and future research at FPL is looking at ways of modifying the standard soil bottle setup to be even more useful for the evaluation of wood and wood protectants. Here are just a few examples of where FPL researchers are pushing the boundaries of the standard soil bottle: Continue reading

Patience is a Virtue: Impressive Decades-Long Research Results

It takes patience to be a scientist. Research can be time consuming, especially when you’re working in the Forest Products Laboratory’s (FPL) Durability and Wood Protection research work unit. Part of the unit’s mission is to treat wood with preservatives and track how long the treated wood can fend off decay. Success can mean decades-long studies.

FPL's Valley View field test site.

FPL’s Valley View field test site.

Recently, several members of the unit made the trek to FPL’s Valley View test site, an unassuming field west of Madison, Wisconsin, where wood in various forms is left to endure the elements, often for years. Their mission: to inspect treated wood stakes that have been buried in the ground for 40 years.

Ground-level view of intact 2 x 4 field stake showing no visible deterioration after more than 40 years of soil contact.

Ground-level view of intact 2 x 4 field stake showing no visible deterioration after more than 40 years of soil contact.

The stakes, both solid wood and plywood, are made of southern pine or western wood species, such as Engelmann spruce and Douglas fir. They were treated with either chromated copper arsenate (CCA) or ammoniacal copper arsenate (ACA).

The results are astounding. There were stakes, both solid wood and plywood, that achieved a rating of 10 (sound) after 40 years of soil contact.  For comparison, untreated southern pine stakes in contact with soil typically last one-and-a-half to two years before failure (rating of zero) due to decay fungi.

Field tests are critical for establishing the durability of treated wood products that are used for construction of decks, bridges, and utility poles. The test site at Valley View has been maintained by FPL since the early 1950’s. Matched sets of many of the studies at Valley View site are also installed in the Harrison Experimental Forest in southern Mississippi, which represents a more severe decay environment due to increased average temperature and rainfall.

Examples of sound (rating of 10) 2 x 4 (top) and plywood field stakes after 40 years of soil contact in southern Wisconsin.

Examples of sound (rating of 10) 2 x 4 (top) and plywood field stakes after 40 years of soil contact in southern Wisconsin.

Blog contributed by Grant Kirker, Amy Bishell, and Stan Lebow.

Wood Preservatives: New Report Explores Directions and Possibilities

A new report has just been published: Wood Protection Research Council, Research Priorities 2013

In this report, authors Carol A. Clausen, Frederick Green III, Grant T. Kirker, and Stan T. Lebow report on findings and recommendations from the Wood Protection Research Council.

Why wouldn’t a homeowner want to build with wood? Sometimes homeowners do not select wood as a building material because of its vulnerability to biodeterioration by fungi and insects under certain conditions of storage and use. These limitations are also a prime cause of user dissatisfaction. Therefore, efforts to protect wood from biological degradation are among the earliest research at the Forest Products Laboratory. This research has successfully reduced the demand for lumber from our National Forests by reducing the need to repeatedly replace existing wood products.

WPRC-cover-art

The cycle of wood harvest, research, and use protects our natural resources.

Wood protection has undergone dynamic changes since the industry voluntarily withdrew chromated copper arsenate (CCA) from most residential uses and new products were introduced to the marketplace. According to the Environmental Protection Agency (EPA), “CCA is a chemical wood preservative containing chromium, copper and arsenic. CCA is used in pressure treated wood to protect wood from rotting due to insects and microbial agents. EPA has classified CCA as a restricted use product, for use only by certified pesticide applicators.”

Obviously, alternatives for wood protection are needed. However, to bring a new preservative to the marketplace, a considerable amount of performance data needs to be obtained. Current laboratory methodologies to determine the durability of test specimens are insufficient, and long-term field testing is required to ensure that a treatment is effective.

Improved accelerated test methods to predict performance would reduce the time needed for the development and acceptance of new preservatives. Potential improvements for accelerated testing may include selection of test fungi, techniques to detect incipient stages of fungal decay, methods to properly assess durability of wood plastic composites use of rapid laboratory bioassays for screening, and field tests that could measure loss in mechanical properties and statistical analysis.

Possibilities and research opportunities abound. For instance, protection systems could be targeted to specific problems. With nanotechnology at the forefront, novel advances in wood protection could replace the broad spectrum biocides traditionally used to inhibit decay fungi. The most logical approach to develop targeted biocides is to take advantage of unique physiological attributes of decay fungi, such as their ability to sequester metals through production of oxalic acid or natural tolerance to preservatives. Discerning and describing these mechanisms may enable us to design specific, targeted inhibitors to control decay and circumvent preservative tolerances that are common in brown-rot basidiomycetes.

This report summarizes presentations and comments from the inaugural Wood Protection Research Council meeting. Research needs for the wood protection industry were iden­tified and prioritized. Methods for successfully addressing research needs were discussed by industry, academia, and association representatives.