Down With Dust!
Canadian Forest Industries
Reprinted from August 2000
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That dust is bound to settle somewhere. In
some cases, you may have to do something about it, and there are now a
variety of options.
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Alternatives to salt product are available, if and when they are needed.
By Craig Pulsifer
You know the scene. The hero tips his hat to the ladies, spurs his horse and gallops off toward
the setting sun in a cloud of dust. What the audience doesn't see is that the rescued damsels are
left choking into their hankies with grit in their eyes.
Today's cowboys mount a different kind of steed - truckers haul on forest roads long past sunset
-- but if the road superintendent hasn't applied an effective dust suppressant in certain areas,
those rigs can still kick up enough fines to deteriorate the road surface and hurt offsite resources.
Airborne dust affects all things roadside - animal, vegetable and mineral. Road dust reportedly
triggers allergic reactions and asthma attacks in some people, making dust-control a health issue
in residential and commercial areas. Safety is also a priority on high-traffic forest roads because
dust creates a visibility hazard. Settling dust also reduces plant vigor and degrades crop value in
agricultural operations. And dust is certainly no friend to engine parts and filters.
For residential and commercial zones, some agricultural areas and hazardous high-traffic areas,
something must he done to keep fines stuck to the road surface.
Dust suppressants work by binding fine particles to larger particles that cannot be swept up in the
back-draft of passing vehicles. In days gone by, oil products were used for this purpose, however,
under various provincial laws and the Federal Fisheries Act, mineral oils are deemed to hurt
fish and fish habitat. The use of oil is now outlawed.
Water Drawing
One group of products, commonly used today is salts like calcium chloride (CaCI2) and
magnesium chloride (MgCI9. Salts are hygroscopic, meaning they absorb ambient humidity to
keep the road surface moist and hold fine particles together. These salts are readily available,
easily stored and can be applied on the company's own schedule, rather than that of a supplier.
Because salts are water-soluble and water dependent, they are effective in a moderate climate
regime; hut if the weather gets too wet, the product tends to leach out and if it gets too dry, there
is not enough ambient humidity.
Every year across Canada, over 100 000 metric tonnes of calcium and magnesium chlorides are
sprayed on dust-sensitive sections of forest haul roads. This is a small fraction of salt compared
to the total amount of road salts, especially sodium chloride (NaC1), used for de-icing the
nation's roads. Nonetheless, it is significant enough for Environment Canada and Health Canada
to include it among 25 substances on their "second Priority Substances List" (PSL2) now being
assessed for the potential risk to the environment and human health. Results from these
assessments will he used to determine whether the substance should be declared toxic under the
Canadian Environmental Protection Act (CEPA).
Results will be released for public comment in August 2000 and may later be posted on the
government web site:
www.ec.gc.ca/ccehl/eng/substances/road.htm.
If, as a result of this study,
road salts are classified as a toxic substance under the CEPA, it is possible that provinces,
municipalities, and other interested parties will he required to establish measures to limit
environmental risks while maintaining roadway safety.
Pulp By-product
Alternatives to road salts are being applied to public and industry roadways these days as costs,
availability and environmental impact factors are weighed together. Several commercial products
are available where the substance itself is the binding agent. One such product is
lignosulphonate, a co-product of the pulping process.
Lignosulphonates are derived from lignin, a naturally occurring polymer found in wood that acts
like glue holding the cellulose fibres of pulp together. During the pulping process, lignin is
separated from the wood and becomes part of the cooking liquor. The liquor undergoes a process
of further evaporation and fermentation to remove volatile compounds like methanol, furfural
and ethanol. The remaining heavy liquor is finally evaporated to about 50% solids and sold as a
liquid or powder ammonium or sodium-based lignosulphonate.
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Completing the cycle - the pulping
of wood products creates lignosulphonates, which in turn can be used as
a dust suppressant on wood haul roads. Tembec's mill in Temiscaming, QC
is one producer marketing that by-product through its Chemical Products
Group under the trade name TDS.
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In preparation for applying the liquefied form of this dust suppressant, roads are first re-crowned
with a grader. The suppressant is then sprayed with a tank truck using application rates of 1.0 to
1.5 liters/m2. The product dries in 20 to 30 minutes to form a hard, durable surface that binds
fines to the larger aggregate particles in the road surface. Because the product does not depend on
ambient humidity for the binding agent, the road surface is maintained in dry weather.
Studies and Standards
In 1998, FERIC released results of a comparison of calcium chloride with a lignosulphonate
product called Tembind, manufactured by Tembec Inc - the product name has since been
changed to TDS. The report concludes that the product is an effective dust control agent in that it
reduced dust production by more than 30% during the first 37 days of the test and by 20% for an
additional 20 days. Economic comparisons were not made during the test. However, Hugh
Hambly, veteran road maintenance supervisor at St. Anne-Nackawic Pulp Company where tests
were conducted, suggests that in that area, costs are similar to those associated with using liquid
calcium chloride.
Not all products are created equal. The name change from Tembind to TDS is largely because of
Tembec's need to distinguish its product from a competing product that was found to contain
high levels of dioxins. As an ISO 9002 registered company, Tembec has developed quality
control procedures geared to meet stringent standards. The environmental integrity of TDS
carefully addresses the issues of phyto-toxicity (i.e. potential to harm plant life), dioxin levels, and
toxicity to livestock and humans.
Classified as non-hazardous by WHMIS, TDS claims to be biodegradable and non-toxic to
plants, animals and humans. It is non-corrosive and will not attack metals or promote rusting. In
fact, TDS is approved for use as an animal feed binder and in liquid animal feed by the Canadian
Department of Agriculture and the U.S. Food and Drug Administration. The product is also used
as a component for concrete admixtures, mineral pelletizers, emulsifiers, dispersants and carbon
black pelletizers.
Care must still be taken when applying any dust suppressant to a roadway, particularly around
water crossings. Provincial guidelines for using suppressants at water crossings might vary as to
the distance it can be mechanically applied from the actual stream perimeter. In some cases, the
application of a suppressant within five to 10 meters of a watercourse must be done by hand
sprayer. Interestingly, the concern for some lignosulphonates is not chemical toxicity, but
biological toxicity.
Mike Kent is the chief environmental officer with the B.C. Ministry of Transportation and
Highways' Engineering Branch. He says, "The concern comes from occasions where
lignosulphonates have been dumped in excessive quantities into streams and there have been fish
kills as a result. This happened on Quadra Island off Vancouver several years ago." In that case,
the product was not TDS, but involved the breakdown of the material's organic components,
which created an unnatural demand on dissolved oxygen in the water that led to the suffocation
of fish.
You might want a home where the buffaloes roam but things are seldom that simple - even dust
can he a complicated matter. So the next time you're about to ride off into the sun set, best tip
your hat to the road supervisor before giving your mount the spurs. Because whether it's fish,
water, crops or family - by the time the dust finally settles, it is bound to land on something dear
to your heart.
Craig Pulsifer is a forest engineer and freelance writer living in BC. In the course of his life, he
has already eaten at least one bucket of dirt.
Canadian Forest Industries
Reprinted from August 2000
