Nordic sawmills release tonnes of volatile organic compounds while drying timber. Finnish researchers believe some of these gases could be captured and sold as chemical raw materials, but converting a promising laboratory result into a profitable industrial process will require far more than placing a filter over a chimney.
The smell surrounding a Nordic sawmill is usually treated as part of the landscape. It is produced by volatile organic compounds released as heat drives moisture, terpenes and other extractives from freshly sawn timber. To most people, it is simply the familiar scent of pine or spruce. To atmospheric scientists it is an emission. To chemical engineers it may also be a dispersed stream of industrial raw materials.
A Finnish research project has attempted to put a value on that stream. Researchers at the University of Oulu report that a sawmill producing 400,000 cubic metres of sawn timber annually could release compounds with an estimated commercial value of at least €279,000 if the mill processes pine and €420,000 if it processes spruce. Those estimates cover the seven compounds that the researchers considered most commercially relevant, rather than every substance detected in the exhaust. More than 100 volatile compounds were identified during the project.
The figures are striking, but they require careful interpretation. They do not demonstrate that a sawmill can earn €279,000 or €420,000 a year by installing recovery equipment. They describe the estimated value of selected compounds theoretically present in the emission stream. The cost of capturing, separating, purifying, testing, storing and selling them has not been deducted. Nor do the figures, as publicly presented, establish the amount of product that an industrial recovery system would deliver continuously at an agreed specification.
That distinction separates a potentially important Nordic bioeconomy innovation from an easy story about money disappearing up a chimney.
From odour to chemical feedstock
The research was conducted through PUUKU, a project examining the recovery and utilisation of volatile compounds released during wood drying. Running from 1 January 2024 until 31 May 2026, it was coordinated by the University of Oulu and had a budget of approximately €400,000. The European Regional Development Fund supplied 80 per cent of the financing, the university contributed about 13 per cent, and the remainder came from the participating sawmill companies Kuhmo Oy, Keitele Timber Oy and Junnikala Oy. The project’s stated objectives included emission control, the recovery of valuable components and optimisation of the drying process from the perspectives of energy efficiency and volatile organic compound management.
The project combined measurements from laboratory ovens with sampling at industrial timber dryers. By scaling the measurements, the researchers estimated total annual flows of volatile substances from commercial sawmills. According to the university, an individual plant can release tens or even hundreds of thousands of kilograms of organic compounds in a year.
The dominant compound was α-pinene, a monoterpene responsible for much of the characteristic scent of coniferous wood. It is already used by the chemical industry in products including adhesives, coatings, disinfectants, fragrances, flavourings and natural-product formulations.
In pine drying, α-pinene represented 66 per cent of the volatile compounds measured and 77 per cent of their calculated value. In spruce, it accounted for 26 per cent of the measured compounds and 33 per cent of the estimated value. The lower share in spruce does not mean that spruce exhaust was economically uninteresting. On the contrary, the project calculated a higher combined value for the seven selected compounds from a spruce sawmill than from a pine mill, apparently because spruce emitted a broader mixture that included smaller quantities of more valuable substances.
The average concentration of α-pinene in the dryer exhaust was reported to be about 80 milligrams per cubic metre of air. This helps explain both the opportunity and the engineering challenge. Large industrial airflows can collectively carry a substantial mass of material, but the commercially useful molecules are highly diluted. A recovery system must therefore process enormous volumes of warm, moisture-laden air to obtain a relatively small flow of product.
This is fundamentally different from collecting a concentrated liquid by-product. The compounds are embedded in a variable gas stream containing water vapour and a complex mixture of organic molecules. The volume and composition can change as a drying cycle progresses and as temperature, moisture content, timber species, age, storage history, heartwood content and resin content change.
A Nordic scientific foundation
The principle that wood drying releases commercially and environmentally significant quantities of terpenes is not new. A 2005 doctoral thesis by Karin Granström at Karlstad University examined volatile organic compound emissions from wood and developed a method for measuring emissions from moist dryer gases.
The method used water vapour to determine the exhaust flow and a dry-ice trap to concentrate volatile compounds and establish the moisture content of the drying medium. The reported uncertainty was 13 per cent at a 95 per cent confidence level. This work addressed an important measurement problem: emissions from industrial drying can be diffuse, wet and difficult to quantify reliably.
Granström also found that drying conditions exerted a strong influence on emission levels. In experiments involving Norway spruce sawdust, emissions of terpenes and total volatile organic compounds rose rapidly when the final moisture content fell below approximately 10 per cent on a wet basis. Higher inlet temperatures also increased monoterpene emissions once the material was below the fibre saturation point.
These findings matter when evaluating the Finnish estimates. There is unlikely to be a single emissions factor that applies uniformly to every Nordic sawmill. A kiln’s operating schedule, target moisture level and energy system may be as important as its total production volume. Two mills processing the same annual quantity of nominally similar timber could generate different recoverable streams.
It also means that recovery cannot be considered separately from drying. If compounds are released most intensely during particular phases, a unit designed to treat a constant average concentration may be inefficient. An effective system may instead need to follow the drying cycle, responding to peaks in flow, humidity and chemical concentration.
The PUUKU programme reflects this connection. Its final webinar in May 2026 included work on compounds from pine and spruce, economic value and markets, vapour-permeation membrane separation, possible further refining, and simulation of dryer energy consumption. In other words, the project did not treat recovery as a stand-alone filter. It considered the wider process in which the emissions are produced.
The difference between capturing and selling
The Finnish researchers tested activated carbon as a means of capturing volatile compounds. According to the University of Oulu, the gases could be trapped effectively and subsequently transferred into a liquid phase. The recovered α-pinene fraction from pine drying had a reported purity of 70 to 88 per cent. The university compared this with a target of approximately 95 per cent for industrial quality.
Reaching 70 to 88 per cent is scientifically encouraging. It suggests that activated carbon can do more than reduce odour or destroy a mixed emission stream. It can concentrate at least one target compound into a fraction that may be suitable for further purification.
It is not, however, the same as producing a market-ready chemical.
A mixed terpene fraction may have value in applications that tolerate variable composition, but buyers of industrial chemicals normally require specifications covering purity, contaminants, water content, oxidation products, consistency and traceability. Depending on the intended use, the material might also require toxicological, environmental or product-safety documentation.
The impurities in the recovered fraction are commercially important. Moving from 70 or 88 per cent purity to 95 per cent is not simply a matter of removing a little more contamination. The remaining compounds may have similar boiling points, molecular sizes and chemical behaviour. Separation can consequently demand heat, pressure changes, solvents, membranes, distillation or combinations of these methods.
PUUKU investigated a semi-permeable membrane and a vapour-permeation approach as part of this challenge. The closing seminar also included a study of further processing routes for the captured volatile compounds. Publicly available project material nevertheless makes clear that separation still requires development.
Activated carbon introduces its own industrial questions. The sorbent has a finite capacity and must be regenerated or replaced. Regeneration requires energy and must release the adsorbed compounds in a controlled way. The process must cope with water vapour, temperature changes, particulates and numerous competing organic substances. Performance measured during sampling or pilot-scale operation cannot automatically be extrapolated to years of continuous industrial duty.
The economic calculation must therefore include more than the market price of α-pinene. It must also cover blowers and pressure losses, vessels and ductwork, carbon consumption and regeneration, thermal energy, condensation, membrane replacement, distillation, instrumentation, maintenance, fire and explosion protection, laboratory analysis and product logistics.
If capture equipment increases the resistance in a dryer’s exhaust system, electricity use may rise. If regeneration relies on steam or heat, that demand must be included in both the financial and environmental balance. If a mill already uses biomass heat and can integrate recovery with surplus thermal energy, the economics may be favourable. If additional fossil energy or expensive electricity is required, part of the environmental benefit could disappear.
A thesis that complicates the optimistic narrative
A master’s thesis at Aalto University provides a useful comparison. In Industrial Potential of Monoterpenes of Scots Pine, submitted in December 2024, Ali Rashid studied monoterpene emissions during the steam drying of Scots pine and investigated the recovery of turpentine from drying condensate.
Six drying experiments were performed at 100°C, 130°C and 150°C, each under relative humidity levels of 50 and 80 per cent. At 130°C and 150°C with 80 per cent relative humidity, only 0.3 to 0.4 grams of turpentine per kilogram of dry wood were recovered from the collected condensates. Under the other tested conditions, no distinct turpentine layer was observed above the water.
When wood chips were subjected to steam distillation instead, the recovery was consistently higher, at three to five grams of turpentine per kilogram of dry wood. Steam-dried chips generally produced between one and four grams per kilogram during subsequent distillation. The dominant compounds included α-pinene and 3-carene, while the concentration and composition varied between individual batches of wood.
These results do not invalidate the PUUKU findings. The experiments involved different processes and recovery routes. Condensation, activated-carbon adsorption and steam distillation are not directly interchangeable. Nevertheless, the thesis illustrates a critical point: the presence of valuable molecules in wood does not ensure that a particular industrial process will concentrate them efficiently.
A commercial recovery system must intercept the compounds where they actually travel. Some may condense with water. Others may remain in the gas phase. Some may adhere to ducts or kiln surfaces, react with oxygen or be transformed by heat. The most appropriate capture technology may therefore depend on the chemical species and the precise conditions under which it is released.
The difference between 0.3–0.4 grams per kilogram in condensate and 3–5 grams per kilogram by steam distillation is also a warning against comparing theoretical wood content with recoverable industrial yield. A value calculation based on the total quantity present in the raw material risks overstating the commercial opportunity if only a small proportion reaches the chosen recovery unit in usable form.
Conversely, the PUUKU measurements were taken directly from drying emissions and industrial exhaust, making them relevant to the actual stream that a recovery system would treat. The next task is to connect those measurements to a complete mass balance. For every tonne of timber entering a kiln, researchers and mill operators need to know how much of each compound remains in the wood, how much enters the exhaust, how much is lost elsewhere and how much becomes saleable product.
Why the spruce number is not necessarily a jackpot
The reported minimum value of €420,000 for seven compounds from a large spruce sawmill exceeds the €279,000 attributed to pine. That result is initially surprising because α-pinene was less dominant in the spruce measurements. It reflects the distinction between concentration and unit value.
Some compounds have extremely high catalogue prices when sold as purified laboratory chemicals in milligram or gram quantities. The university gives the example of germacrene D recovered from spruce-drying exhaust. As a pure laboratory chemical, it can command a quoted price of more than €580 per milligram. Multiplying that figure to obtain a notional price per kilogram produces an extraordinary number, but the project itself acknowledges that the compound occurs in tiny quantities and is difficult to isolate. Its annual value is consequently low.
This is an important safeguard against inflated bioeconomy claims. A catalogue price for a tiny package of an analytical standard is not the price an industrial producer would receive for kilograms or tonnes. At larger volumes, the pool of specialised buyers may be limited, the market price may fall sharply and the recovered substance may not initially satisfy the purity requirements of the catalogue product.
The most credible business case is therefore likely to involve compounds that combine three features: substantial emitted volume, an established industrial market and a separation route that does not consume most of the product’s value. The PUUKU team reached a similar conclusion, identifying the best prospects among chemicals emitted in relatively large quantities and used widely as industrial feedstocks, even when their price per kilogram is comparatively modest.
This makes α-pinene a more persuasive initial target than a rare molecule with a spectacular laboratory price. Pine mills may offer the simplest starting point because α-pinene dominates both the emitted mixture and its estimated value. A relatively concentrated target is easier to capture and upgrade than a complex stream whose value is distributed across numerous minor compounds.
The environmental case could be broader than the product revenue
For sawmills, the commercial incentive is only part of the calculation. Volatile organic compounds contribute to industrial emissions and can participate in atmospheric chemistry. Recovery may help a plant reduce its environmental load, control odour and prepare for tighter emission requirements.
PUUKU was explicitly framed in the context of developing environmental regulation and the need to prevent, clean and recover gaseous emissions. The project also examined drying optimisation, connecting emission control with energy efficiency.
This creates the possibility of a combined business case. A system that is only marginally profitable from chemical sales could still be attractive if it also lowers the cost of emission control, reduces regulatory risk or improves community relations. In areas where sawmill odour affects nearby residents, a recovery system might have social value even if its recovered product does not independently repay the investment.
The strongest environmental claim would require a life-cycle assessment. Capturing α-pinene from a sawmill might displace material produced through another industrial route, but the benefit would have to be weighed against the energy, sorbents and equipment used for recovery. The fate of spent activated carbon, membrane materials and low-value residues would also need to be included.
The analysis should define the alternative as well. If the exhaust would otherwise be discharged untreated, recovery could reduce emissions directly. If a mill would otherwise use thermal oxidation, a capture process might avoid destroying useful carbon but could require a more elaborate separation system. If the recovered mixture is eventually burned because it fails to meet product specifications, the environmental advantage may be smaller than initially claimed.
A potential Nordic platform, not yet a proven industry
The wider Nordic forest sector provides favourable conditions for developing the concept. Finland and Sweden have large, technically sophisticated sawmilling industries, established forest-industry research networks and significant experience in pulp-mill side streams, tall oil, turpentine and bio-based chemicals. Norway and Denmark add expertise in process engineering, membranes, energy systems and specialised chemical markets.
The region also has a practical reason to collaborate. No single sawmill may produce enough of every minor compound to support independent refining. Several plants could instead supply mixed concentrates to a central facility, where the material would be separated and upgraded. Such a structure would resemble other industrial ecosystems in which dispersed by-products are aggregated before refining.
This model would introduce transport and stability questions. Monoterpenes can oxidise and change composition during storage. A crude recovered stream may contain water or reactive impurities. Storage tanks, tankers and handling systems may require controls for flammability and vapour emissions. Centralised refining becomes viable only if the recovered material remains sufficiently stable and valuable after these costs.
An alternative would be to focus on one abundant fraction, such as α-pinene, and use it locally or sell it into an existing chemical value chain. This could reduce the need to isolate every trace compound. The optimal model will depend on whether buyers accept a technical-grade mixture or demand highly purified individual substances.
The three sawmill companies involved in PUUKU gave the project direct industrial relevance, but the publicly available results do not yet constitute a commercial demonstration. The research has established that valuable substances are present, that over 100 compounds can be identified, that activated carbon can capture them and that an α-pinene-rich fraction can reach 70 to 88 per cent purity. It has not publicly established a complete investment case for full-scale continuous operation.
The figures industry now needs
Before companies can judge whether the opportunity is worth pursuing, the next phase must provide several connected sets of evidence.
First, there must be full mass balances for complete industrial drying cycles and preferably for different seasons, timber sources, species and product dimensions. Average concentrations alone are insufficient if most of the recoverable material appears during short peaks.
Secondly, researchers need to report capture efficiency. The quantity entering the exhaust is not the same as the quantity adsorbed by activated carbon, recovered during regeneration or retained after purification. Each stage has its own yield.
Thirdly, a continuous pilot installation should record pressure loss, energy consumption, sorbent lifetime, membrane performance, water management and maintenance requirements. The process should operate long enough to reveal fouling, corrosion and deterioration that short trials may not capture.
Fourthly, product samples need assessment by potential buyers. A nominal purity figure does not show whether the mixture meets a particular customer’s specification or whether troublesome impurities can be removed economically.
Finally, a transparent techno-economic analysis should separate gross compound value from recoverable revenue and net operating return. It should include sensitivity to energy prices, utilisation rates, raw-material variability, market prices and the scale of the installation.
The €279,000 and €420,000 estimates are useful as indicators of where a resource may exist. They should not be presented as anticipated annual profit. Even if every calculated euro could be realised as sales, a recovery plant would still need to cover capital expenditure, operating costs, financing and commercial risk. In practice, the value retained by the sawmill would be only a fraction of the gross chemical value.
Yet it would be equally premature to dismiss the opportunity because the first calculations are incomplete. Industrial symbiosis often starts by recognising that a dilute emission or low-value residue contains something useful. Over time, improvements in separation technology, energy integration and market organisation can convert an environmental cost into a product stream.
PUUKU has moved the idea beyond speculation. It has measured real sawmill emissions, identified target compounds, investigated capture and separation, and produced an initial estimate of economic scale. The scientific case for continuing is strong.
The commercial case remains open.
For the Nordic forest industry, that is precisely why the research matters. The familiar scent of sawn timber may represent neither an effortless fortune nor merely a harmless smell. It is a complex industrial stream containing carbon, chemical value and environmental liability. The challenge is to recover enough of that value, at sufficient purity and with sufficiently low energy use, to make the invisible resource worth more than the machinery required to catch it.
Photo: Petri Österberg
Sources
- University of Oulu, “Sahatun puun tuttu tuoksu voi olla satojen tuhansien eurojen arvoista”, 21 September 2026. University news article. [oulu.fi]
- University of Oulu, PUUKU project description, funding information and published project results. Project page. [oulu.fi]
- University of Oulu, programme for the PUUKU closing webinar, 19 May 2026. Webinar page. [oulu.fi]
- Ali Rashid, Industrial Potential of Monoterpenes of Scots Pine, master’s thesis, Aalto University, 2024. Aalto University repository. [aaltodoc.aalto.fi]
- Karin Granström, Emissions of Volatile Organic Compounds from Wood, doctoral thesis, Karlstad University, 2005. DiVA record. [diva-portal.org]
