For a detailed profit potential analysis please visit economics section for pallet kilns.

Study on the effects of heat treating a load of pallets. Before and after pictures plus weight loss can seen below.

During a heat treatment process we are not trying to dry the pallet and the vents stay closed throughout the heat treatment period. During the heat treatment cycle a little drying will occur, normally about 3-7%. You will probably find that a pallet will dry more on a flat bed truck during transport than during the heat treatment process.

On recycled pallets, which are generally much drier, do not have the same moisture available in the pallet and a few more defects are likely. Since customers of recycled pallets are not looking for the same visible quality as customers of new pallets, this does not seem to be a problem. If you or your customer find that you would like to reduce the drying defects a high pressure spray system can be installed to help bring up the relative humidity faster.

A direct gas heating system will create a little drier climate than an indirect heat systems, such as hot water coils, steam coils, or tube based indirect gas heating. Indirect heating systems tend to use 15-25% more energy than direct gas heating systems.

Study of effects of heat treating pallets with Direct gas fired heating system.

This test was performed at Granville Pallet Company in North Carolina during the certification run. Timber Products Inspection has certified the kiln and the facility. They also will be performing the monthly inspections.  This test and comparison run was performed in one our our end-loaded High Capacity Standard pallet kilns with a direct gas heating system.

Based on this and earlier certifications we have the following comments:

• - We see very little or no drying signs on the pallets.
• - During treatment the pallets loose 1-7 pounds, which is about a moisture content loss of 2-10%. This is probably less than the drying that occurs during transport on a open flat bed trailer.
• - The most common visible sign of drying is a split at the end of the deck board where the nail is placed. But rarely there is any sign of drying on the stringers.
• - This test run was on pallets with 1 7/8" stringer and the more common 1 1/8" stringer should cut 30-35% off the heat up time.
• - We have seen very little or no cupping or twisting on the top and bottom boards.

Documentation from this test run: temperature readings by TPI during the certification. (146 KB pdf)

For this certification process we took pictures of and weight of eight pallets before and after the heat treatment process to learn more about the actual effects of using direct gas heating. Please view the collected information and pictures in the table below.

Before	After
Weight: 66 lbs	Weight: 59 lbs
Weight: 72 lbs	Weight: 68 lbs
Weight: 53 lbs	Weight: 50 lbs
Weight: 75 lbs	Weight: 72 lbs
Weight: 74 lbs	Weight: 73 lbs
Weight: 72 lbs	Weight: 71 lbs
Weight: 72 lbs	Weight: 72 lbs
Weight: 70 lbs	Weight: 68 lbs

Yes all Kiln-direct pallet kilns are also designed to dry pallets efficiently but there is more to drying pallets efficiently and economically than meets the eye. In most cases it more about what is "good enough" than perfect drying to a certain moisture content. Below we have compiled an estimated / theoretical energy consumption and cost to dry 1 GMA pallet.

The drying process in the table above is probably a 20-24 hour drying time. But it will depend on wood species, type of pallet, incoming MC%. Light drying often takes around 12 hours and will help reduce the chance of mold and will in many cases be sufficient. Thorough drying will often take 20-24 hours and in some cases longer.

Of course saying 5 cents per pallet is easy and only a general rule of thumb. Based on our customer experience we have seen costs as low as 2 cents during the summer using natural gas and up to 15 cents in the winter (in Indiana) using LP gas.

We have also heard claims that some kilns only use 1 cent per pallet, which is possible on pallets that weigh 20-30 lbs, 1" stringers, and with a starting temperature of 90 F; however, this is not your typical run. Basicly, all systems use about the same amount of energy to heat the pallets plus a waste factor. The energy waste factor will depend on the chamber insulation (more is better and no thermal conductors), heat system efficiency (direct heat is higher/better), adequate and even air flow (too little will extend the process), and length of treatment period (shorter is better). So when comparing the hype from different kiln manufactures look at the building and design facts to make an educated choice. We believe it is important for you to realize that the energy cost is only a small portion of the total cost of heat treating pallets.

Let us first warn you that this detailed answer is a little bias to our own system and we will be blowing our own horn a little bit. Since we feel very fortunate that we have designed kilns that help reduce and eliminate this problem from the beginning.

Mold can attack lumber that is above a certain moisture content (most experts believe this critical moisture level to be between 22% to 30%). Although most heat treatment processes (except direct steam heat treating) removes some moisture from the pallets it is not sufficient to get the pallets sufficiently dry to eliminate or minimize the conditions for mold to attack and grow. Actually, based on our current experiences the heat treatment process may push some of the moisture and sugar to the surface. This provides mold with both good conditions to develop and grow and may even make mold a little more likely on heat treated pallets than non-heat treated pallets.

How to solve this problem:

1. Cool down the pallets properly:
This is probably the most common method we see to significantly reduce the potential of mold. Cool down can either happen by leaving the pallets for 4-8 hours in a well ventilated area of fresh air. If you have purchased a Kiln-direct pallet kiln you also have the option of making the cool down part of the heat treatment cycle. All our kilns have high capacity power exhaust that allow for efficient cool down of the pallets and remove surface moisture as part of the HT cycle.
The cooling down has two significant benefits for reducing the potential of mold. First, if a load of hot pallets (not dried) is placed directly into a container or van they will cool down by releasing moisture and creating a water saturated climate, during the warmer weather this makes mold almost certain if the pallets are left in the container/van for several days. Secondly, when you cool down the pallets while still in the kiln for up to 2-3 hours you will be removing a significant amount of surface moisture and latent heat energy. This means they do not "steam" up the container or van in the same way as before. Furthermore, most of Kiln-direct pallet kilns use a direct gas heating system with also creates a drying climate during the whole process = a drier surface = lower chance of mold.

2. Kiln drying pallets
You can kiln dry pallets and crating components in about 15-20 hours in most situations (Some lumber drying experts still claim that it will take 4-7 days, but we have proven otherwise). This drying brings the average moisture content to 15-25%. This should be sufficient to minimize the chance of mold (not eliminate totally, but minimize the chance). Not all kiln systems can accomblish this in the mentioned time frame. But nearly all Kiln-direct pallet kilns have been designed for drying standard stringer (also oak) pallets in the mentioned time frames.

3. Chemical treating
A few of our customers use an anti-fungicide to eliminate or reduce mold on both heat treated and non-heat treated pallets. This can either be done as part of the production line with a spray booth or in a separate dip tank.

First and foremost you do not need to purchase a certified kiln, since it is your facility that needs to be certified. You should however be certain that the kiln components/design or the turn-key kiln either has been certified at other facilities or meet the specifications of the inspection agency. You can actually build your own chamber based on your own design as long as it passes the inspection. Kiln-direct kilns have passed certification by several of the inspection companies and this is usually always accomplished in one day.

We are developing detailed answer, please return soon for the detailed answer.

Steam was initially seen as the solution by many kiln experts and it had many characteristic that made it the obvious choice. It was speculated that dry heat would probably damage the pallets, which would not be an issue with direct steam heated.

The key to efficient and fast heat to 56C or 133F is to have a wet bulb temperature significantly higher than this. You can achieve this high wet bulb temperature either by higher humidity or high dry bulb temperature. We found that raising the dry bulb was the most practical. During many actual test runs on pallets we have found that it is no problem using temperatures as high as 250-300F (120-150C) in the kiln without any significant signs of damage to the pallets. This seems unbelieveable on the surface, but the pallet is only dried by about 3-10%, which is not sufficient to create any damage.

Another significant advantage in raising the dry bulb temperature is that a little more drying occurs, this helps reduce the chance of mold after the heat treating process, which is a big problem with steam heating pallets.

As mentioned above this is a rather difficult question to answer without specific information about the pallet. Even then we have a hard time estimating the actual heat treatment time. Below we have listed the factors that have an influence on the treatment time and the theory behind this.

Major factors that determine the treatment time:

1. Initial starting temperature
This is obvious, but lets examine it a little. We will take water as a standard for this example. It takes one BTU to heat one pound of water one degree The same is true for pallets as well, not taking the energy waste into account. If it takes 2 million BTU's (586kw) to raise the temperature from 85F to 135F in a load of pallets, it will take 4 million BTU's (1172kw) to raise the temperature from 35F to 135F. Why? The temperature differential from 135 to 85 is 50 degrees and the temperature differential from 135 to 35 is 100 degrees; twice as much difference means twice as much energy is needed.

2. Thickness of the largest piece of wood in the pallet
This is obvious and based on our experience it seems like the length of the heat treatment time will increase propotionately with the thickness of the wood. You can compensate some by increasing the chamber temperature. A pallet with thicker wood (such as a block pallet) will not necessarily need more energy. Therefore, it will allow the heating system to achieve a higher chamber temperature faster, since the pallet consumes less energy per hour.

3. Size of the heat source
The heat source is a little like a bottle neck, either it provides enough heat and the process is not slowed or it is not able to provide sufficient heat. However, in the very beginning of the process the size of the heat source is directly related to the speed with which the pallets are heated. The thinner the largest wood piece is on your pallets the more the latter statement is true.

4. Adequate air flow
The air in the kiln acts as the heat transfer agent between the heating source and the pallets. As the air becomes more humid it is able to carry more energy to the pallets per cubic foot/meter of air. This is one of the reasons it is desireable to have a very well sealed chamber (the other is to achieve a high humidity to avoid drying defects). Adequate air flow means not too little and not too much. Too much air flow may actually dry the pallet during the initial heat up period when the air has not become saturated with moisture. As part of the air flow equation one should also consider the lenght of air travel from entering the pallets to existing. Naturally the pallets on the existing side will recieve less heat and reach the required treatment temperature last. Reversing the fans may help reduce this problem. It is our experience that 40-50 feet is maximum when using reversing fans.

Leasing a pallet kiln can often be the best economical choice. Advice about this should be left to professionals, such as your CPA, financial consultant, or in house financial officer. We do have a few pointers in choosing a leasing company. First, we have always believe in shopping around for the best rates, but you must be careful. Having many companies run a credit check on the company can reduce its rating and your future ability to obtain good rates. Although limiting the amount on the application with leasing companies will also limit competition but it is wise to do so.

We have both worked with leasing companies on turn-key kilns and on kilns constructed locally. Often it will be easier to obtain better rates and conditions on the turn-key solution, since it can easily be moved to another locations.

We will provide you with a short and extended list. The extended list will generally apply to older units located in a remote area without easy access to maintain parts. These lists are based on our standard design with direct gas heat system, such as the turn-key pallet kiln.