Radiofrequency (RF) heating was evaluated as an alternative to methyl bromide fumigation and conventional heat treatments for wood packaging material. RF heating was found to meet the ISPM-15 requirement of achieving 60°C within 30 minutes and could treat wood dimensions greater than 20cm. RF heating also resulted in more uniform and consistent heating compared to microwave heating, and faster heating times for dimensions over 6x6 inches. RF heating is a viable alternative for treating wood packaging material according to international standards.

1. Background
• “Pallets move the world” with several billions pallets
(>90% wooden) in service worldwide
• More than $400 billion worth of US trade exported
annually on wood pallets
• Untreated wood packaging material (WPM) a major
pathway by which pests that infest wood spread
among countries e.g. Asian longhorned beetle
(ALB, Anoplophora glabripennis) and the emerald
ash borer (EAB, Agrilus planipennis)
• Estimated urban impact of ALB in the US is the
loss of 35% of total tree canopy cover and a value
loss of $669 billion , while EAB threatens to
eliminate most ash species from North America.
ISPM-15 and its limitations
• ISPM-15 (International Standards for Phytosanitary
Measure No. 15) adopted by the International Plant
Protection Convention aims to significantly reduce
the risk of pests moving in WPM used in
international trade by the following treatments:
– Fumigation with Methyl Bromide-MB
– Heat treatment
• Conventional Heat treatment-HT (56˚C for 30min)
• Dielectric heating- DH (60˚C through wood profile
for 1min)
• MB phasing out in line with Montreal Protocol while
conventional heat-treatment is costly & time
consuming (Fig.1)
• Dielectric heating (DH) includes microwave (MW)
and radiofrequency (RF) heating. The major
difference between them is frequency range: RF
uses much lower frequencies (10 to 300 MHz) than
MW (300 to 30,000 MHz)
• DH is a viable alternative for MB treatment but
current ISPM-15 includes restrictions over its
application on size of treatment load (< 20cm) and
treatment time (within 30 min)
• A footnote in the annex to ISPM-15 also states that
only MW has been proven to comply with the
schedule of 60˚C for 1 min within the 30 min
treatment time, which excludes RF as an approved
treatment.
Acknowledgments
USDA-NIFA Methyl Bromide Transitions Grant
Program (Grant 2012-51102-20208)
Results Conclusions
• RF heating meets ISPM requirement of
achieving 60˚C within 30 min and can be
used as an approved treatment
(Table1, Fig 3)
• RF heating can penetrate beyond the 20 cm
dimensional limit (Table1, Fig 3)
• RF heating is more uniform, consistent and
faster than MW heating, especially for
dimensions greater than 6”x6” (Fig 4 & 5)
1Manoj K Dubey, 1John Janowiak, 2Kelli Hoover, 3Ron Mack and 3Peggy Elder
1Dept. of Agricultural & Biological Engineering, 2Dept. of Entomology, Penn State University, 3USDA-APHIS
Work in Progress
• Commercial scale RF trials in Forestville, NY
• Measurement of dielectric properties of
various species of wood
• Comparative economic analysis of RF heating
vs. conventional heating
• Extension activities to educate & promote
adoption of RF technology
12
Objectives
Comparisons of RF and MW heating at similar
power settings to demonstrate:
• Ability of RF to treat beyond 20 cm dimension
• RF can meet requirement of achieving 60˚C
through the wood profile within 30 min
• Superior heating uniformity and less time to
achieve 60˚C (t60) through the profile of test
specimens of varying dimensions using RF
Experimental approach
• Cants of dimensions ranging from 4”x4” to
10”x10” prepared from white oak (Quercus
alba)- most commonly used species for pallet
construction in US
• Specimens drilled at mid-length and pre-fixed
depth from wood surface for probes to monitor
core temperatures (Fig 2-a, 2-b)
• Specimens heated in 19 MHz RF (Fig 2-c) and
2.45 GHz MW (Fig 2-d) lab ovens with similar
power (3.4kW) till all probes recorded target
temperature of 60˚C.
• Specimens processed for moisture content
determination & thermal imaging analysis
Further Information
Dr John Janowiak, +1-814-865-3916, jjj2@psu.edu
Cant size
(inch)
Heatin
g
Depth
t60
(min)
Moisture
Content %
Moisture loss
%
(cm) RF MW RF MW RF MW
4x4 9 4 4 61 65 0.5 1.6
5x5 11 11 7 59 66 0.7 1.1
6x6 14 10 11 69 61 0.8 1.5
8x8 19 20 34 67 54 0.5 6.4
10x10 24 30 54 62 58 N/A N/A
0
20
40
60
80
100
120
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
ΔT(°C)
Distance from Top surface (inch)
ΔT (Final temp - Start temp) with heating
depth in 8”x8” cant
RF MW
0
10
20
30
40
50
60
9 11 14 19 24
t60(min)
Heating Depth (cm)
Time to achieve 60˚C at varying heating depth
RF MW
ISPM-15 DH Treatment Time Limit
Fig.1
Fig.2-a
Fig.2-dFig.2-c
Fig.2-b Fig.3
Fig.4
Fig.5
Table 1
Key references
FAO (2013). ISPM-15: Regulation of wood packaging material in international trade.
Rome, International Plant Protection Convention-IPPC, Food and Agriculture
Organization of the United Nations
Strutt, A., J. A. Turner, L. Garrett, R. A. Haack, and L. Olson (2013). Evaluating the
impacts of an international phytosanitory standard for wood packaging material: Global
and United States implications. Forest Policy and Economics 27:54–64.