CODES, CRITERIA AND MORE

Provincial Medium Density Fibreboard (MDF) Emission Guidelines

Last Updated: June 1995

Medium density fibreboard emission guidelines have been developed for total particulates, formaldehyde and opacity.

Medium density fibreboard (MDF) consists of small wood fragments and sawdust, resin (usually urea-formaldehyde) and wax bonded together under high pressure to form a uniform manufactured board with the usual finished dimensions of 4 feet by 8 feet. It is commonly used for furniture, cabinetry, and door and window frames.

The Provincial Health Officer, the Ministry of Health, and the Environmental Quality Branch of the Ministry of Environment have identified particulate matter and formaldehyde emissions from MDF facilities to be of considerable concern. The process of driving off moisture from the resin-wood mixture (drying) is the largest single source of particulates from a typical MDF operation. Formaldehyde is also usually released due to the application of urea-formaldehyde resin before drying. In addition, formaldehyde is released from the presses where the resin is activated and the materials are bonded together.

Options for controlling emissions from MDF plants are classified as process modifications or add-on control technologies. The two primary areas for their application are the press vents and the dryers, the areas that generate most of the emissions. For formaldehyde control, the process modification for the press vents is to route emissions into the plant's energy system because it operates under high temperature, and will effectively eliminate the formaldehyde. Process modifications for dryers include reducing temperatures to prevent formaldehyde from being driven off, injecting formaldehyde scavengers, and applying resin after the dryers using mechanical techniques in place of air injection systems. All these process modification approaches contribute to reduced atmospheric emissions.

Two add-on control technology options that can be effective in reducing both particulate and formaldehyde emissions are biological gas cleaning and thermal oxidation.

Biological gas cleaning involves the use of microorganisms and is in the process of being implemented as a pilot study in the wood products industry. Thermal oxidation is a combustion process which has been installed at one MDF plant, and plans are underway for using it at other plants. Although thermal oxidation reduces particulate and formaldehyde emissions, it requires high temperatures and the use of additional fuel. This technique results in carbon dioxide and nitrogen oxide emissions being increased.

After reviewing the various emission control options and other regulatory requirements for MDF plants, and after consulting with industry, consultants and environmental groups, the Ministry developed the following emission guidelines for new MDF plants:

(a) For combustion sources, reference conditions are 20°C, 101.325 kPa, and dry gas concentration corrected to 8% flue gas oxygen by volume.

(b) Monitoring is to include a breakdown of particulate emissions into size fractions of PM10 and PM2.5

(c) Multiple manual source tests within a one day period until a continuous monitoring procedure acceptable to the ministry has been developed.

These guidelines are to be used as guidance for a regional manager in setting permit limits.

For More Information:

Environmental Quality Branch
Ministry of Environment
Government of British Columbia

PO Box 9341
Stn Prov Govt
Victoria, British Columbia
Canada V8W 9M1
http://www.env.gov.bc.ca/air/