Wood Pellets and Storage Safety

By Anna Simet | February 05, 2013

This morning, I came across a story about how the U.K. Health and Safety Executive (HSE) issued a warning to raise awareness of certain issues involved in using wood pellets as fuel.

The HSE is advising people to take precautions regarding the storage of wood pellets, because apparently carbon monoxide released from their storage has been responsible for nine deaths in Europe since 2002, most recently a pregnant 28-year-old Swiss woman.

I looked up the notice, which was issued in November. It said:

Wood pellets for boilers are normally stored in a large sealed hopper/tank or a storage room that has a screw feeder (auger) connected to the boiler. Alternatively, the hopper/tank can be mounted over the boiler for gravity feeding. Due to the enclosed nature of these hoppers/tanks/rooms, the atmosphere inside can become oxygen depleted and a toxic atmosphere containing carbon monoxide can accumulate. The chemical reactions responsible for carbon monoxide production from wood pellets are assumed to be an auto-oxidation process, especially oxidation of the fatty acids to be found in wood.

The HSE points out that even small quantities of wood pellets can produce life-threatening quantities of carbon monoxide in a confined space, and that various factors affect the amount produced. These including the age of the pellet, the temperature in the room, the wood type, and the amount of oxygen present.

The HSE is advising all those who use, install, maintain or distribute wood pellet boilers and/or manufacture, store, and distribute wood pellets to consider a detailed list of check points. Here are a few of them:

-Wood pellet hoppers/tanks/storage rooms and boilers should always be installed and commissioned by a competent person, normally approved by the manufacturer/supplier. This is particularly important if the installation involves the replacement of a coal-fired boiler, where existing boiler room and storerooms are often utilized.

 -Do not enter the pellet storage area or place your head into a wood pellet hopper as they can contain toxic gases. No personnel should enter the hopper/tank unless fully trained and competent in confined space entry procedures. It is recommended that the store room is ventilated at all times, either mechanically or by being designed to have a through draft.

 -Ensure that the boiler and pellet feed mechanism etc. is cleaned and serviced by a competent person as specified by the manufacturers' instructions.

-If any problems are encountered with the unit, such as the system not heating correctly or flue gas is flowing into the boiler room, turn the unit off and contact the supplier and/or manufacturer and request assistance.

 - Warning signs should be placed on the pellet storage area access door, ideally on both sides so it can be seen when the door is open. The warning sign should include the following information:

DANGER - RISK OF CARBON MONOXIDE POISONING - There is a danger to life from odorless carbon monoxide and lack of oxygen. Check atmosphere before entry with an appropriate device. No entry for unauthorized persons. Keep children away from the storeroom.

While most of the time safety seems to be common sense, the truth is that it’s not. Something that seems so trivial, such as the manner in which one is storing wood pellets, could result in tragedy. As wood pellet heat continues to expand in the U.S. and elsewhere, it's important to create awareness of such issues.

I thought the timing of this blog was appropriate, as we here at Biomass Magazine/Pellet Mill Magazine are in the middle of putting together the March issue, which is themed plant safety and regulatory compliance. I’m confident we’ll be able to provide you with some valuable insight  from industry experts regarding these issues.