A practical approach to the burning of beetle infested trees

The burning of trees affected by the Asian Longhorned Beetle in a confined residential area
by means of S-Series air curtain burners

by N. Fuhrmann

Literature and guidelines from government agencies, schools and industry organizations on the subject of the management of trees and other vegetation infested with the Asian longhorned beetle and, for that matter, other tree destroying beetles, pests or fungi, are plentiful. Once affected or suspected trees have been identified, it is generally accepted that the optimal method of containing and eradicating the pest, that is, preventing the colonization of the beetles in areas of healthy trees, is to fell and burn the beetle infested trees.

But how can burning be accomplished in a confined area, possibly a quarantined residential district, without causing a menace or endangering the well-being of the public, as transporting the affected wood waste to other more suitable location is ruled out?

Many experts suggest to chip the trees and then burn the chips, without any advice where and how to burn them. Grinding or chipping may make the wood waste more manageable for transport to remote locations for disposal or incineration by whatever means, but it is only one step towards the goal of complete destruction of the trees.

 It is also sometimes suggested that chipping is all that is needed to eradicate the beetles, because it will result in the total elimination of them, as the mechanical trauma inflicted will kill the beetles and none will survive. No conclusive scientific evaluation of this premise can be readily obtained, and common sense may dictate that many, if not most adult beetles could well be killed by the mechanical chipping procedure, but eggs or larvae and some mature beetles may quite certainly survive the ordeal and result in re-populating of the pest in the same or other locations, if the produced chips were transported off site and then stored or disposed.

The optimal and most cost effective solution to the apparent dilemma is to incinerate the infested trees on site in sections as large as practical in an S-Series air curtain burner without any costly prior grinding or chipping. An S-Series machine is a portable refractory walled incineration system or mechanized burner with a fire box that is usually 21 or 27 feet long, capable of accommodating large sections of tree trunks. After felling a tree, it only needs be cut into suitable chunks which are immediately introduced into the burning chamber of the S-Series machine on site or nearby by means of a front loader or excavator. At a loading rate of approximately 8-15 tons or more per hour (throughput depending on type of system used and factors, such as make-up and moisture content of waste stream, etc.) this process is efficient and economical.

Air Burners, LLC Model S-127: Shown in full operation - No visible smoke!

The system controls smoke quite effectively, and its emissions are regulated by EPA provisions for air curtain incinerators. High velocity air is introduced into the burning chamber in such a way that over-oxygenation of the fire is achieved, resulting in temperatures of about 2,000 to 2,500 degrees Fahrenheit (!) and particulates are trapped under the air curtain and effectively combusted.

The patented S-Series is being manufactured by Air Burners, LLC. of Palm City, Florida and can be procured directly from the manufacturer. The largest portable machine costs slightly more than $100,000 FOB factory. S-Series machines are also available for contract work or lease from a number of environmental or recycling companies, and for larger projects, also from the manufacturer.

What makes the S-Series machines the only practical machines for burning trees in quarantined or otherwise confines areas, especially close to occupied dwellings, is the fact that they are totally portable for quick and easy deployment to trouble spots. They arrive fully assembled and, with the right kind of trailer, require no crane, but only a winch, for loading and unloading. An S-Series System machine is powered by a Diesel engine, and it needs no external electric power or natural gas to achieve combustion, as it feeds on the very waste that is introduced into it. Operation as near as 100 yards to occupied dwellings is usually permitted, as the menace from smoke and emissions is very controlled. It is again the extremely high temperature that causes most particulates to be rapidly combusted within the chamber.

But it is this very high temperature that also assures complete sterilization of the beetle affected wood waste (or for this matter, any other combustible waste, such as pathogen-ridden diseased animal carcasses), leaving absolutely no chance for re-colonization, re-infestation or spreading. The residual ash is actually a beneficial soil amendment for certain clay-like soils and can be safely and with confidence applied to the land.

That is not true for any other remedy, especially affected tree management by means of grinding, mulching or chipping. That method should be avoided altogether in favor of S-Series incineration.

Other considerations along the same line:

Municipalities that opt to acquire an S-Series machine will find applications for it at operations, such as municipal landfills, for the economical reduction of wood waste consisting of yard waste or certain demolition debris, including hard to manage stumps, reserving the scarce and costly landfill space for other waste deposits. S-Series units are being employed for such purpose at landfills where they are operating day after day for many years.

This incineration option has gained significance, as the chipping of wood waste has often not been as desirable a solution as it was suggested to be. This has been recently shown again with respect to storm clean-up measures in the Florida Keys, Alabama and other locations that suffered from hurricane storm damage in recent years.

If stored in the open, wood chips will start to decompose and leachates from them may adversely affect the water table. In addition, the chipping itself is quite expensive, because the grinding equipment may cost several times that of an S-Series unit, and related transportation and possible disposal cost of the resultant chip piles are high as well. The chips frequently cannot be marketed for beneficial re-use and must be taken to an appropriate landfill at significant cost. Subsequent burning in an S-Series machine, as is often requested, is not very practical. Only chunks of wood waste without any prior grinding or chipping can be efficiently handled by the S-Series incinerator.

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