As part of their leading role in Work Package 10, the Environmental and Techno-Economic Assessment of Superheated Steam Drying — researchers from the University of Santiago de Compostela (USC) have just published a peer-reviewed study that lays the scientific groundwork for evaluating the sustainability of industrial drying technologies. USC’s Group of Environmental Biotechnology (Biogroup) is coordinating this critical workstream within SteamDry, and this publication is a direct output of that work.
The article is out now, fully open access, in the journal Environmental Technology & Innovation:
“Toward the decarbonization of industrial drying technologies: Cross-sector sustainability, economics and efficiency integrated assessments with emphasis on the wood and paper industries”
José Luis Ares-Sainz, Ana Arias, Gumersindo Feijoo & María Teresa Moreira
Environmental Technology & Innovation, 2026 .
Why Drying Matters for Industrial Decarbonization
Industrial drying is often an invisible process — yet it is one of the most energy-hungry operations in manufacturing. In the wood industry, the drying stage alone consumes 50–70% of the total process energy. In paper production, that figure rises to 60–80%. At the European level, 91% of the energy used for industrial heating and cooling still comes from fossil fuels, making drying a critical pressure point in the path toward net-zero emissions by 2050.
This is precisely the challenge that the SteamDry project was designed to address. And this new publication is a cornerstone contribution to that mission.
What the Paper Does
This critical review, conducted in accordance with PRISMA guidelines, systematically analysed 59 scientific articles published between 2004 and April 2025, covering drying technologies used in the wood and paper industries. The study evaluated each technology across three dimensions:
- Energy performance, using Specific Energy Consumption (SEC, in MJ per kg of evaporated water) and energy efficiency as standardised benchmarks.
- Environmental sustainability, through the lens of Life Cycle Assessment (LCA) methodology.
- Economic viability, via Techno-Economic Analysis (TEA).
The result is one of the most comprehensive cross-sector assessments of industrial drying published to date.
Key Findings
The Wood Industry: Significant Potential for Improvement
Conventional kiln dryers — the industry standard — show an average SEC of 3.80 MJ/kg of evaporated water. But more efficient alternatives are already available:
- Heat-pump-assisted kilns reduce SEC to an average of 2.39 MJ/kg, a 37% improvement.
- Hybrid solar dryers with heat pumps can push SEC as low as 0.75 MJ/kg — the most sustainable option identified for wood drying.
- High-temperature kilns and optimised air velocity strategies have shown reductions of 35–59% in energy consumption compared to conventional systems.
- Superheated steam drying achieves SEC values of 0.7–1.0 MJ/kg, though it remains underexplored at industrial scale.
The Paper Industry: Optimisation Over Transformation
In paper manufacturing, research has focused more on refining existing technologies than introducing radically new ones:
- Multi-cylinder dryers (85–90% of the industry) show an average SEC of ~3.3 MJ/kg and efficiency close to 75%.
- Yankee dryers (used mainly for tissue paper) present higher consumption, around 4.7 MJ/kg.
- Infrared dryers are the least efficient, with averages around 6.5 MJ/kg.
- Emerging solutions like heat pumps and superheated steam could reduce paper drying energy use by 17–34%, respectively.
A Clear Gap in Sustainability Assessment
Despite broad consensus on the need to decarbonise drying, the systematic review reveals a striking gap in the use of standardised assessment tools:
- Only 10 out of 59 articles applied full LCA methodology (ISO 14040–14044).
- Only 11 out of 59 articles applied any form of Techno-Economic Analysis.
- Just 1 study applied LCA exclusively to the drying stage itself.
- A total of 32 different environmental indicators were used across studies — making comparison across technologies extremely difficult.
This lack of harmonisation is a key barrier to informed decision-making and to demonstrating the real benefits of new drying technologies to industry and policymakers.
Environmental Impact: What We Know So Far
Despite limited data, available LCA evidence paints a clear picture of how much drying matters for a product’s environmental footprint:
- Kiln drying increases the global warming impact of redwood lumber by ~34 kg CO₂ eq/m³ compared to equivalent green (undried) products.
- In oriented strand board (OSB) production, the drying stage contributes 25–27% of the total climate change impact.
- In the paper sector, switching from a natural gas boiler to a high-temperature heat pump for steam generation can reduce greenhouse gas emissions by ~40% under the European electricity mix.
- Solar-assisted wood drying systems can avoid between 26 and 66 tonnes of CO₂ per year depending on the configuration and climate.
The Road Ahead
The paper calls for a more coordinated research agenda across the sector. Specifically, it recommends:
- Standardising SEC and energy efficiency definitions across studies to enable meaningful comparisons.
- Integrating LCA and TEA from the outset of technology development, not as an afterthought.
- Scaling up evaluation of emerging technologies — heat pumps, solar-assisted dryers, and superheated steam systems — from pilot projects to industrial demonstrations.
- Expanding environmental assessments beyond carbon footprint to include impacts such as particulate matter, land use, and resource depletion, particularly as low-carbon alternatives are adopted.
Relevance for SteamDry
This publication provides the scientific foundation that directly informs the SteamDry project’s work. Superheated steam drying — the core technology of our project — emerges from this review as one of the most promising pathways for decarbonising industrial drying, with SEC values up to five times lower than conventional kiln drying. Yet, as the paper confirms, it remains underrepresented in the scientific literature, especially at industrial scale.
SteamDry is here to change that. This review maps exactly where the knowledge gaps are — and where our project is uniquely positioned to fill them.
Access the Full Paper
The article is published as open access and is freely available to all readers:
📄 Read the full paper: https://zenodo.org/records/21786324
