Wood packing is used in importing bulk goods into the United States to prevent shifting during ocean travel. Under regulation 7 CFR 319.40--Importation of Logs, Lumber, and Other Unmanufactured Wood Articles--the Port Operations Unit of USDA's Animal and Plant Health Inspection Service quarantines solid-wood packing materials that could potentially harbor plant pests. The wood packing is either fumigated with methyl bromide or heat treated at 71.1 °C for 75 minutes.

"Fiber Fuel International is developing a steam sterilization process as a methyl bromide alternative to fumigation of quarantined wood waste from shipment packing," says Glenn White, project manager with Fiber Fuel International, Inc. (FFI) in Savannah, GA. "We have several goals for this project. Not only will this be one alternative to methyl bromide fumigation, but it will also save landfill space by recovering imported wood waste. This recovered wood will be a clean, low-cost feedstock for biofuel and renewable energy products."

Sometimes, during the process of unloading the imported articles, the wood is broken or damaged and is not reusable. The ships store the broken wood on board, until they can dump it into the ocean. However, MARPOL V, a U.S. and world maritime regulation, charges penalties for dumping wood waste within 25 nautical miles of shore. Offenders could receive a fine of up to $500,000 and 6 years' imprisonment.

"Dumping the wood into the ocean is not an alternative. This dumped wood has washed up on our shores, littering beaches and ecologically fragile barrier islands. Floating wood waste causes safety problems for fishing boats off the coast of Savannah, GA," says White.

This project to use steam to sterilize quarantined waste wood is a partnership between FFI and two Swedish firms, Winbergs and NYPRO. A prototype of the Swedish steam sterilization vessel, tested and approved by USDA, was found effective in destroying plant pests. During the sterilization process, the wood goes through a grinder and is then conveyed to an enclosed bin where the chips are metered by volume into the steam sterilizer and treated at 105 °C at 0.5 bar pressure for 5 minutes. This process successfully kills pests in the wood. (For more information, see David Dwinell's technical report, "Alternatives to Methyl Bromide for Eradicating Pests in Exported Softwood Chips, Lumber, and Logs," in the October 1996 issue of this newsletter.)

The steam sterilization vessel is about 10 meters long and 2 meters in diameter, and has butterfly valves with stuffing glands at each end to ensure atmospheric integrity. A chain-plate conveyor acts as a treatment table and as a chip carrier inside the vessel. Steam is directly injected into the vessel through a multiport manifold directly onto the wood chips, resulting in sterilization with reduced moisture content.

"The sterilized wood chips can be used in our patented fuel process for cofiring wood with pulverized coal in utility boilers or in smaller boilers that need to use a cleaner fuel than is presently being used. Cofiring wood with coal reduces the pollution produced from the burning of coal," says White.

If USDA certifies development and testing of the equipment and sterilization process, FFI will market the licensed process to shipping ports and waste recovery companies throughout the United States. Of about 79 ports monitored by USDA, about half are now using methyl bromide on quarantined wood waste.

"The fumigated wood is placed in landfills or can be used as mulch. In the future, our steam sterilization process can make quarantined wood waste into a clean, renewable fuel," says White.

USDA's Oxford Plant Protection Center in North Carolina is examining a compliance agreement for this alternative to methyl bromide. This project is supported by the Southeastern Regional Biomass Energy Program, which is administered by the Tennessee Valley Authority for the U.S. Department of Energy.