United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-94/036 April 1994
Project Summary
Evaluating ACQ as an
Alternative Wood Preservative
System
Abraham S. C. Chen
This evaluation addresses the waste
reduction/pollution prevention and eco-
nomic issues involved in replacing
chromated copper arsenate (CCA) with
ammoniacal copper/quaternary ammo-
nium (ACQ*) as a way to preserve wood.
The evaluation was conducted at
McArthur Lumber & Post Co., Inc., in
McArthur, OH. The most obvious pollu-
tion prevention benefit gained by using
ACQ is eliminating the use of arsenic
and chromium, both of which generate
hazardous wastes and a risk of con-
taminating the environment via chemi-
cal spills. Because most treatment
plants are self-contained in that they
reuse all wastewater produced within
the plant and on the drip pads, no liq-
uid waste problems were addressed for
either the CCA or the ACQ treating pro-
cess.
The ACQ system generates more air
pollution than does the CCA system,
mainly as ammonia (NH3). For a plant
with an annual production of 1
million ft3 (or about 20 million board
feet), 90,000 Ib of NH would be released
per year from the ACQ treatment op-
erations and the ACQ-treated wood. In
contrast, a CCA plant in Virginia annu-
ally producing four times as much
treated wood released < 0.021 Ib of ar-
senic (as As2O5) and only trace amounts
of chromium (as CrO3) and copper (as
CuO). During air monitoring of CCA
treatment, airborne concentrations of
inorganic arsenic were above the Oc-
* Mention of trade names or commercial products does
not constitute endorsement or recommendation for
cupational Safety and Health Adminis-
tration (OSHA) permissible exposure
limit (PEL) of 0.01 mg/m3. Full-shift per-
sonnel .exposures to ammonia during
ACQ treatment were below applicable
exposure limits, but exposures to am-
monia during unloading of the ACQ
treating cylinder were above the short-
term personnel exposure limit of
35 ppm.
The treated wood, after being trans-
ferred from the drip pads to the out-
side storage yard, could become a
major source of contamination. For a
plant with an annual production of
1 million ft3 (or about 20 million board
feet) of CCA-treated wood at 0.4 Ib/ft3
retention, 157lb of As2O6, 1,506lb of
CrO3, and 39 Ib of CuO could be washed
away by stormwater every year. For
the same amount of ACQ-treated wood,
at the same retention, 1,299 Ib of CuO,
3,148 Ib of total organic carbon (TOC)
(inclusive of extractable wood
organics and quat [as didecyldi-
methylammonium ion, or DDA]), and
3,172 Ib of NH4+ could be released into
the stormwater runoff every year. It
must be noted that these releases were
estimated based on exposure of all
treated wood to about 18 in. of rainfall
4 days after treatment.
Converting from CCA to ACQ would
require a capital investment of about
$191,000. The operating costs for ACQ
wood treatment would be higher — a
net expense of up to $1,100,000. More
than 71% of that net expense would be
used to purchase ACQ chemicals.
Therefore, switching from CCA to ACQ
-------
would not produce any immediate quan-
tifiable benefits. Because the economic
analysis did not take into account fac-
tors such as long-term liability, safety,
and the company's public relations, the
real benefit of using ACQ could be more
than what it would appear.
This Project Summary was developed
by the EPA's Risk Reduction Engineer-
Ing Laboratory, Cincinnati, OH, to an-
nounce key findings of the research
project that is fully documented in a
separated report of the same title (see
Project Report ordering information at
back),
Introduction
The objective of the U.S. Environmental
Protection Agency's (U.S. EPA's) Re-
source Conservation and Recovery Act
(RCRA) Problem Wastes Technology
Evaluation Program is to evaluate, in a
typical workplace environment, examples
of innovative technologies that demon-
strate a potential (1) to reduce or, prefer-
ably, eliminate the use of RCRA-banned
metals, including arsenic, in various in-
dustrial and agricultural applications, or
(2) to minimize the RCRA problem wastes
through recycling and recovery. The goal
of this study was to evaluate the use of
ACQ as an alternative to CCA for pre-
serving wood. Specifically, this study evalu-
ated (1) ACQ's waste reduction/pollution
prevention potential and (2) the econom-
ics. The long-term effectiveness of ACQ
or CCA as a preservative was not exam-
ined, because such evaluations require a
lengthy test time (e.g., 1 to 5 years) and
many resources. However, ACQ's ability
to protect wood and the chemical and
physical properties of ACQ-treated wood
have been studied recently by many re-
searchers.
The wood-preserving industry uses pri-
marily waterborne arsenical preservatives
for wood treatment. Because of the solu-
bility of arsenic compounds in water, wood
treaters have been using mixed-salt pre-
servatives for wood treatment since the
early 1910s. The mixed-salt preservatives
usually contain various arsenic compounds
and metal salts from the metals
chromium (Cr), copper (Cu), or zinc (Zn).
Currently, the most predominant arsenical
preservative used in the United States is
CCA-Type C (per the American Wood-
Preservers' Association [AWPA] Standard
P5-92).
Because of its toxicity and carcinoge-
nfc'rty, arsenic poses a serious threat to
the environment and human health. In-
creasingly stringent federal and local regu-
lations concerning arsenic have been
proposed and enacted. Because about
70% of the total arsenic demand is used
to produce industrial chemicals such as
arsenical wood preservatives, the arsenic
consumption would be greatly reduced if
the use of CCA and other arsenical wood
preservatives could be eliminated or re-
duced.
These concerns have prompted a
search for more environmentally friendly
wood preservative systems for wood treat-
ment. The alternatives must be safe ,to
handle during treatment, the treated prod-
ucts must be safe to use, and the alterna-
tives must effectively protect wood against
decay, marine borers, and insects. Fur-
ther, the alternatives must not leach from
the treated wood to the environment. Eco-
nomics also should be considered, al-
though there may exist harder-to-quantify
justifications such as reduced liability,
greater safety, better morale, and improved
company public relations.
This study evaluated ACQ, a relatively
new, commercially available wood preser-
vative system that was developed and
patented in Canada. It is a two-chemical-
component preservative system comprised
of ammoniacal copper and quat. The com-
bined biocidal effect of copper and quat
protects wood from biodeterioration and
exhibits relatively low mammalian toxicity
and environmental impact. ACQ was ap-
proved and commercially used first in
Scandinavian countries in 1988 and, more
recently, in Japan. In the United States,
two ACQ formulations have been accepted
by the AWPA Preservatives Committee
as preservative standards.
Waste Reduction and Pollution
Potential Evaluation
Pollution prevention is achieved prima-
rily by reduction of waste at the source.
Pollution prevention considers all waste
types, such as hazardous waste, solid
waste, wastewater, and air emissions.
Reductions must be true reductions in vol-
ume and/or toxicity of waste and not sim-
ply a transfer of waste from one medium
to another.
The waste reduction potential was mea-
sured in terms of volume reduction and
toxicity reduction. The reductions were
quantified by comparing waste volumes
and types from the CCA treatment pro-
cess with those produced by the ACQ
treatment process. Volume reduction ad-
dressed the gross wastestream, such as
chemical spills, air emissions, and
stormwater runoff. Toxicity reduction con-
sidered concentrations and types of con-
taminants, such as As, Cr(VI), and Cu in
the CCA gross wastestream versus NH3,
total organic carbon (TOC), and total
Kjeldahl nitrogen (TKN) in the ACQ gross
wastestream. The pollution prevention po-
tential also considered hazards that any
toxic emissions might pose to workers. Air
quality was measured in terms of airborne
metal concentrations and NH3 concentra-
tions. The results of these measurements
would determine the proper safety attire
to be worn by the plant operators:
During wood treatment, it is necessary
for a treatment plant to maintain good
housekeeping practices and to avoid any
major chemical spills in and around the
plant. Dirt, dust, and debris on the drip
pads must be collected and disposed of
according to applicable regulations. How-
ever, the characteristics of solid wastes
were not evaluated because little was ac-
cumulated on the drip pad after either
treatment.
Air Emissions and Worker
Exposures
During CCAjnd ACQ wood treatment,
As, Cr(VI), Cu, and NHa could be emitted
to the air as toxic contaminants. There-
fore, air samples were collected and ana-
lyzed to ascertain approximated full-shift
(8-hr) and short-term (15-min) occupational
exposures to these contaminants. National
Institute for Occupational Safety and
Health (NIOSH) sampling devices were
positioned in the employee's breathing
zone or in stationary locations. Exposures
were calculated as the time-weighted av-
erage (TWA) of the full-shift and 15-min
samples. The Drager tube, a semi-quanti-
tative detecting device, also was used to
obtain a rough estimate of ammonia con-
centrations which, in turn, were used to
obtain estimates of NH3 emission quanti-
ties from the stack (vent).
During CCA wood treatment, airborne
concentrations of inorganic arsenic were
above the OSHA PEL of 0.01 mg/m3
among all workers and in all monitoring
locations. The highest concentration of
0.12 mg/m3 was measured at the door to
the CCA treating cylinder. The full-shift
and short-term exposures to Cr(VI) and
Cu, however, were less than OSHA PEL,
NIOSH Recommended Exposure Limits
(RELs), and American Conference of Gov-
ernmental Industrial Hygienists (ACGIH)
Threshold Limit Values (TLVs). No stack
test or isokinetic test was performed; how-
ever, a CCA treatment plant in Virginia
that in 1992 treated four times as much
wood as McArthur Lumber & Post emitted
only 0.021 Ib As2O5 that year.
During ACQ wood treatment, the 8-hr,
TWA concentrations of NH3 ranged from
0.45 ppm to 8.4 ppm, less than 35% of
the NIOSH REL and ACGIH TLV-TWA of
25 ppm. The short-terrn exposure of 38
2
-------
ppm, measured in the breathing zone of
the drip pad ground man during unloading
and stacking of ACQ-treated lumber, ex-
ceeded the short-term exposure limit of
35 ppm recommended by OSHA, NIOSH,
and ACGIH. Using the ammonia concen-
trations measured at the vent and at the
treated wood, an annual ammonia emis-
sion of up to 90,000 Ib would result if the
treatment plant were to treat 1 million ft3
(or about 20 million board feet) of com-
modities per year.
Stormwater Runoff
After the treated wood units had re-
mained on the drip pad for 4 days, two
36 in. x 42 in. x 8 ft wood units (each
consisting of 42 pieces of rough-cut tim-
ber, 6 in. x 6 in. x 8 ft) from each treat-
ment were subjected to artificial rainfall on
the drip pad. One untreated unit served
as a control. The wood units tested were
.stacked crosswise on top of three or four
similar units spaced approximately 4ft
apart (see Figure 1), with a sheet of heavy-
duty polyethylene liner placed underneath
each of the top units. The separating lin-
ers then were arranged as illustrated in
Figure 1 to allow collection of runoff di-
rectly under each of the top units. A gar-
den sprinkler placed about 6 ft above the
floor and about 9ft away from the units
tested was used to produce artificial rain-
fall. The amount of rainfall, as measured
by five rain gauges, ranged from 0.6 to
0.9 in./hr during a 20- to 21-hr period. The
runoff collected within the liner boundary
flowed to a 32-gal plastic container. At
different time intervals, the volume of the
runoff was measured and runoff samples
were taken for testing for heavy metals
(including As, Cr, and Cu), total suspended
solids, total dissolved solids, pH, TKN,
and TOO. After sampling, the water in the
plastic containers was disposed of to the
cylinder door pits.
Significant amounts of As and Cr were
leached from the CCA-treated wood units.
Arsenic concentrations up to 8.84 mg/L
were found in the runoff samples collected
during the first 2 hr; the As concentrations
slowly decreased to between 2.36 and
3.67 mg/L after 17 hr. Chromium concen-
trations ranging from 58.8 to 78.5 mg/L
were detected during the first 2 hr and
remained at 16.1 to 20.5 mg/L after 17 hr.
The amount of Cu leached was less; only
3.05 to 3.84 mg/L was detected during
the first 2 hr.
The mass of each CCA active ingredi-
ent leached in 24 hr was calculated by
adding together the products of the con-
centration of each sampling interval and
the corresponding runoff volume. Some
concentrations were estimated based on
best-fit curves. The percentage loss of
each active ingredient, therefore, could be
estimated by dividing the mass lost by the
amount of that active ingredient absorbed
by a wood unit. The active ingredient ab-
sorbed by wood could be calculated by
multiplying the specific retention of that
ingredient by the wood volume having CCA
penetration. As a result, the percentage
loss would range from 0.16 to 0.27% for
As, from 1.08 to 1.67% for Cr, and from
0.08 to 0.13% for Cu.
Copper concentrations up to 288 mg/L
were found in the ACQ runoff samples
collected during the first 5 hr; the concen-
trations tapered down to 28.7 to 72.2 mg/
L after 20 hr. TKN up to 620 mg/L was
measured initially; its concentrations de-
creased to 154 to 265 mg/L after 15 hr.
TOG as high as 890 mg/L was analyzed
during the first 2 hr; its concentrations were
reduced to 170 to 382 mg/L after 15 hr.
The TKN analyzed was attributed prima-
rily to didecyldimethylammonium (DDA) ion
and ammonium (NH4+) ion and, to a lesser
extent, to nitrogen-containing wood orgari-
ics. The TOC analyzed comprised mainly
the organic carbon of water-soluble wood
organics and DDA ion.
The percentage loss of each ACQ ac-
tive ingredient in 24 hr was estimated us-
ing the method discussed earlier. The
percentage loss was 0.69 to 1.02,% for
Cu, 3.84 to 5.52% for TOC (inclusive of
extractable wood organics and quat [as
DDA]), and 3.23 to 3.82% for NH3. It must
be noted, however, that up to 41% of NH3
had been assumed to have been lost dur-
ing air drying. This assumption was made
according to a laboratory test done by an
ACQ vendor.
The yearly losses of the CCA and ACQ
active ingredients through stormwater run-
off were estimated and are presented in
Table 1. For small-sized plants with an-
nual production of 1 million ft3 (or about
20 million board feet), the plants could
release 157 Ib of As2O5, 1,506 Ib of CrO3,
and 39 Ib of CuO every year. For me-
dium-sized, large-sized, and very large-
sized plants, the annual release would
increase proportionally. Converting from
CCA to ACQ would significantly reduce
the release of toxic metals, but the re-
lease of other less toxic contaminants
would greatly increase. For example, a
small-sized plant could release 1,299 Ib of
CuO, 3,148lb of TOC (inclusive of ex-
tractable wood organics and quat [as
DDA]), and 3,172lb of NH4*, and the re-
lease from medium-sized to very large-
sized plants also would increase
proportionally.
Economic Evaluation
Cost comparisons were made for CCA
versus ACQ. Converting from CCA to ACQ
would require a capital investment of
$191,000. The operating costs for ACQ
were higher; a net expense of up to
$1,100,000 was required, 71.3% of which
would be used to purchase ACQ chemi-
cals. Based on an ACQ vendor, the sell-
ing price for every 1,000 board feet of
ACQ-treated wood would be $55 more
expensive than that for CCA-treated wood
(including $37 for chemicals, $4 for pro-
duction, $9 for lumber stacking and cap-
ping, and $2 for longer shed turnaround).
Conclusions and
Recommendations
The waste reduction and pollution pre-
vention potential for ACQ are summarized
in Table 2. The data presented are based
on a treatment plant with an annual pro-
duction of 1 million ft3 (or about 20 million
board feet). Of course, the most obvious
benefit gained by using the ACQ system
is the complete elimination of As and Cr
use, which eliminates the generation of
hazardous wastes and the risk of con-
taminating the environment via chemical
spills. Because most treatment plants are
self-contained in that they reuse all waste-
water produced within the plant and on
the drip pads, no liquid waste problems
need to be addressed for either CCA or
ACQ.
The ACQ system produces a greater
amount of air emissions, mainly as NH3.
For an annual production of 1 million ft3
(or about 20 million board feet), 90,000 Ib
of NH3 would be released per year. In
contrast, a CCA plant that produced four
times as much commodities released only
< 0.021 Ib of As2O5 and trace amounts of
CrOq and CuO every year. During the air
monitoring of the CCA treatment, how-
ever, airborne concentrations of inorganic
arsenic were above the OSHA PEL of
0.01 mg/m3 among all workers and in all
monitoring locations. Therefore,, appropri-
ate respiratory protection should be used
until engineering controls are in place to
reduce exposures to acceptable levels.
During ACQ treatment, full-shift personnel
exposures to ammonia were below appli-
cable exposure limits. Ceiling exposures
to ammonia during unloading and stack-
ing of ACQ-treated lumber on the drip
pads exceeded the short-term exposure
limit of 35 ppm. Those working in the im-
mediate areas must use appropriate res-
piratory protection. Engineering controls
also should be considered to reduce ex-
posures.
-------
I
Flguro t. ACQ-treatad and control wood units with plastic liners (A) and sprinkler setup (B).
-------
Table 1. Yearly CCA andACQ Losses Due to Leaching
Yearly CCA andACQ Loss (thousand Ibfyr)
Plants with Annual Production (million ft 3)
2 3 4
CCA Ingredients
As (as ASgOg)
Cr(asCrOJ
Cu (as CuO)
0.20
1.92
0.05
0.40
3.84
0.10
0.60
5.76
0.15
0.80
7.68
0.20
1.00
9.60
0.25
ACQ Ingredients
Cu (as CuO)
quat(asDDA)
NHf (as NH3)
2.76
6.69
6.74
5.52
13.38
13.48
8.28
20.07
20.22
11.04
26.76
26.96
13.80
33.45
33.70
(a) DDA = didecyldimethylammonium ion.
Table 2. Summary of Yearly Pollution Prevention Potential for ACQ Wood Preservative Systems "»
Environmental
Media/Concern
Liquid waste
Solid waste
Air emissions
CCA
None
75 to 100 Ib hazardous waste/yr
<0.021 Ib As-OJyrVl
ACQ
None
75 to 100 Ib hazardous waste/yr
90.000 Ib NHJvr
Trace CrO,
Trace CuO
Stormwater runoff
200lbAssO.
1,920 Ib CrO
SOIbCuO
Trace CuO
2,760 Ib CuO
6,690 Ib quat (as DDA)
6,740Ib A/W/ (as NH3)
(a) Assuming 1 million ft3 annual production.
(b) Arsenic emission of a CCA treatment plant that treated four times as much wood as McArthur
Lumber & Post in 1992.
The treated wood, after being trans-
ferred to the uncovered storage yard, could
become a major source of contamination
to the environment. For a CCA treating
plant with 1 million ft3 (or about 20 million
board feet) of annual production, 157 Ib of
As2O 1,506 Ib of CrO3, and 39 Ib of CuO
could be washed away annually by
stormwater. For an ACQ treating plant
with the same amount of annual produc-
tion, 1,299lb of CuO, 3,148lb of TOG
(inclusive of extractable wood organics and
quat [as DDA]), and 3,172 Ib of NH/ could
be released annually. Converting from
CCA to ACQ totally eliminates the release
of As and Cr to the environment.
Although converting to ACQ requires a
capital investment and higher operating
costs, the benefits of reduced long-term
liability, greater safety, increased morale,
and improved public relations for the com-
pany as a result of using ACQ can be
significant.
The full report was submitted in fulfill-
ment of Contract No. 68-CO-0003 by
Batteile Memorial Institute under the spon-
sorship of U.S. Environmental Protection
Agency.
•&U.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-067/80226
-------
-------
-------
A.S.C. Chen Is with Battelle Memorial Institute, Columbus, OH 43201-2693.
Paul Randall is the EPA Project Officer (see below).
The complete report, entitled "Evaluating ACQ as an Alternative Wood Preser-
vative System," (Order No. PB94-159928; Cost: $27.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/036
------- |