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Where do the emissions come from?
- The wood chip or bark boiler heats the timber kilns and emits dust, NOx and CO. At 1–50 MW it is a medium combustion plant under the Swedish Ordinance on Medium Combustion Plants (SFS 2018:471).
- The timber kilns dry almost all sawn timber in compartment or progressive kilns. The exhaust air contains terpenes and other volatile organic compounds from the wood, measured as TVOC.
- The sawdust or pellet dryer dries the raw material from 50–55 % moisture content to 8–12 %. The exhaust from the dryer contains dust, TVOC and formaldehyde, and combustion gases if the dryer is heated directly by flue gases.
- Mills, presses, coolers and extraction systems from the saw line and the planer give wood dust, which is separated in cyclones and filters. The requirements are set case by case in the permit or in the decision on the notification.
Which rules apply?
| Plant | Regulation | What it means for the measurement |
|---|---|---|
| Boiler of 1–50 MW for wood chips, bark or sawdust | The Swedish Ordinance on Medium Combustion Plants (SFS 2018:471) | Registration. Periodic measurement of dust, NOx and CO at least every three years up to 20 MW and every year above 20 MW, the first time within four months of registration |
| Boiler whose flue gases dry the sawdust directly | Exempt from SFS 2018:471, section 15, point 4 | No measurement requirements from the ordinance; the requirements are in the permit or the decision on the notification, and the measurement is made at the dryer outlet |
| Sawmill with more than 70,000 m3 of sawn timber per year | Permit required (category B), chapter 8, section 3 of the Swedish Environmental Permitting Ordinance (SFS 2013:251) | Conditions for the boiler, dryers and extraction with parameters and intervals. Annual environmental report by 31 March |
| Sawmill with more than 6,000 m3 per year | Notification required (category C), chapter 8, section 4 | The municipality can order precautionary measures, for example a dust condition with a measurement interval. Self-monitoring, but no annual environmental report |
| Pellet or briquette plant, more than 5,000 m3 of raw material per year | Notification required (category C), chapter 8, section 5 | As above. The boiler is assessed separately: notification above 500 kW, permit above 20 MW (chapter 21, sections 10–11) |
| Boiler with at least 25 GWh of useful energy per year | The Swedish NOx charge, NFS 2016:13 | Continuous NOx measurement with your own equipment, which an accredited laboratory checks every year with a comparison measurement. Declaration by 25 January |
The permit or the decision on the notification can set stricter requirements, and the ordinance applies on top of the conditions (section 17). The statutory text is what applies.
What is measured – and what is typical?
The boiler's values are the ordinance's limit values. Dryers have no limit values in Swedish law; for comparison: the BAT-associated emission levels (BAT-AELs) for particle dryers in the wood-based panels industry, the levels the EU's BAT conclusions give for well-run plants.
| Parameter | Why in this industry | Typical level or requirement | Method |
|---|---|---|---|
| Dust, the boiler | Ash and unburnt material; the cyclone or filter decides the level | Boiler in operation by 2018: 50 mg/Nm3 up to 20 MW, 30 above 20 MW; sawmills 150 (above 5 to 20 MW) and 50 (above 20 MW) up to and including 2029. New boiler: 50, 30 or 20 by size | EN 13284-1 |
| NOx, the boiler | From the fuel's nitrogen and at high temperature | 300 mg/Nm3 for solid forest biomass, all sizes | EN 14792 |
| CO, the boiler | A measure of the combustion; always measured (section 43) | No limit value in the ordinance; the permit can set one | EN 15058 |
| Dust, the sawdust or pellet dryer | Fine particles follow the drying air | Condition in the permit. Comparison: BAT-AEL 3–30 mg/Nm3 for a directly heated dryer (18 % O2), 3–10 for an indirectly heated one | EN 13284-1 |
| TVOC, dryers and timber kilns | Terpenes from the wood are released as it dries | Condition in the permit. Comparison: BAT-AEL < 20–200 mg/Nm3 for particle dryers, not applicable when pine is the main raw material | EN 12619 (FID) |
| Formaldehyde, the dryer | Formed when wood is heated | Condition in the permit. Comparison: BAT-AEL < 5–10 mg/Nm3 for particle dryers | CEN/TS 17638, 2–60 mg/m3 |
mg/Nm3 means dry gas at 0 °C and 101.3 kPa, for the boiler at 6 % O2 (section 38); that is why O2, moisture, gas flow and temperature are always measured. SO2 has no limit value for solid forest biomass. The BAT-AELs for the panels industry, (EU) 2015/2119, bind only panel plants and are given as the average of three measurements of at least 30 minutes. The boiler's level depends on fuel, load and flue gas cleaning.
What the measurement year looks like
Establish what applies
Read the permit or the decision on the notification, and the monitoring programme. A boiler of at least 1 MW must be registered under SFS 2018:471, unless its flue gases dry the sawdust directly.
Periodic measurement of the boiler
We measure dust, NOx and CO, plus O2, moisture and gas flow, while the boiler runs stably at representative load (section 46), at the ordinance's intervals.
Dryers and extraction as the conditions say
Dust, TVOC and formaldehyde from the dryer, and dust after cyclones and filters, are measured as often as the conditions say, preferably in the same visit as the boiler. A performance test on a new boiler or dryer can be included.
The NOx charge where it applies
At 25 GWh or more of useful energy per calendar year, NOx is measured continuously and the equipment is checked every year with a comparison measurement according to NFS 2016:13.
Report, environmental report and records
You receive an accredited report with the concentrations in mg/Nm3 dry gas at 6 % O2. Sawmills with a permit submit the annual environmental report by 31 March; measurement results and the registration certificate are kept for at least six years (section 56).
Dates that apply up to 2030
The limit values in SFS 2018:471 have applied since 1 January 2025 to boilers above 5 MW that were put into operation by 19 December 2018. Boilers of 5 MW or less must be registered by 1 January 2029 and meet the values from 1 January 2030. The sawmills' higher dust value applies to combustion up to and including 2029, and not in zones where the environmental quality standard for particulate matter is exceeded. From 2030, 50 and 30 mg/Nm3 respectively apply to sawmill boilers too.
What does a measurement cost at a sawmill or pellet plant?
The price depends on how many sources are to be measured (boiler, dryers, extraction) and which parameters the conditions require. The dryer exhaust is moist and cool, so the sampling takes longer than in a hot flue gas. The accessibility of the measurement site and the travel distance also play a part. Request a quote – we reply within two working days. Approximate prices for the most common measurements are in the price guide.
Frequently asked questions
What emission requirements apply to a sawmill with an 8 MW wood chip boiler?
The boiler is registered, and dust, NOx and CO are measured at least every three years under SFS 2018:471. Limit values at 6 % O2: 300 mg/Nm3 NOx and 50 mg/Nm3 dust for a boiler in operation by 19 December 2018 (30 for a newer one), for sawmills 150 mg/Nm3 dust up to and including 2029.
The boiler's flue gases pass through the sawdust dryer. Does the ordinance still apply?
No. Boilers whose flue gases are used for direct drying of material are exempt (section 15, point 4). The Swedish Environmental Protection Agency's explanation of the exemption is that the stack emission then does not reflect the combustion alone. The requirements are in the permit or the decision on the notification.
Must we measure the emissions from the timber kilns?
No ordinance requires it. The permit may have a condition on TVOC, and then we measure with an FID according to EN 12619. The emission consists mostly of terpenes from the wood.
Do we need to measure SO2 and CO?
CO must always be measured in the periodic measurement (section 43), although the ordinance has no limit value for it. SO2 has no limit value for solid forest biomass and need not be measured. Straw and peat have other values.
Are we covered by the NOx charge?
Only if a boiler delivers at least 25 GWh of useful energy in a calendar year; 10 MW of heat reaches that in about 2,500 hours. NOx is then measured continuously, and the equipment is checked every year with a comparison measurement.