Iceland is rare: a real-world case study of a nation almost entirely powered by renewable energy. Thanks to a meticulous new analysis, Iceland is showing us what low-impact hydropower can actually look like.
A new study by researchers at EFLA Consulting Engineers and Landsvirkjun [64.1°N, 21.9°W], Iceland’s national power company, dives deep — and we mean 100 years deep — into the carbon footprint and environmental impact of four major hydropower stations. The study reveals important nuances in how truly “green” even renewable energy can be — and offers lessons for countries like Canada, Norway, and Scotland, where mountainous terrain and glacial rivers are ready-made for hydroelectric power.
How Clean Is Clean Energy?
While hydropower produces no emissions during generation, building a dam, digging tunnels, and flooding a valley are not environmentally neutral. The researchers used a full life cycle assessment (LCA), which means they looked at everything — from mining the steel for turbines to maintaining machinery for a century.
They assessed four of Iceland’s largest hydropower stations:
- Blanda (NW Iceland)
- Fljótsdalur (E Iceland)
- Búðarháls and Búrfell II (S Iceland)
Together, these represent half of Iceland’s hydropower capacity. Each station is built on glacial rivers, with dams and reservoirs carefully integrated into remote landscapes.
The Numbers: Carbon Footprints That Matter
Over their 100-year lifetime, the stations generated between 250 and 653 times more energy than they consumed. That’s a remarkable energy return on investment — far higher than fossil fuel systems and even some other renewables.
But what about carbon?
- The carbon footprint ranged from just 0.5 to 21.1 grams of CO₂-equivalent per kilowatt hour (gCO₂-eq/kWh).
- Three of the stations stayed under 1.5 gCO₂-eq/kWh, far lower than solar, wind, or nuclear.
- The exception was Blanda, at 21.1 gCO₂-eq/kWh — still far below the EU’s 100 gCO₂-eq/kWh threshold for sustainable electricity.
Why the difference?
At Blanda, more vegetation and carbon-rich soil were flooded to make reservoirs, releasing biogenic greenhouse gases like methane as the organic matter decomposed. This is a reminder that even renewables can emit more than expected if not managed carefully.
Significance to the Boreal Region
This study is especially relevant to Northern Europe and Canada, where glacial rivers, highland basins, and existing hydropower infrastructure mirror Iceland’s landscape. In these regions:
- New dams may not be necessary — smart extensions to existing plants (like Búrfell II) can yield big gains with minimal impact.
- Soil quality and vegetation matter — choosing sites with low organic carbon can reduce reservoir emissions.
- Transmission bottlenecks can block efficiency — the study found that limited grid capacity prevents Iceland from getting the most out of its hydro plants.
So if you’re planning new hydro projects, this isn’t just about the river — it’s about the whole system, from valley floor to power line.
Designing for the Long Term
Each station was assessed over a 100-year period — the expected lifetime of the dams and powerhouses. Electromechanical components (like turbines and generators) were assumed to be replaced once, after 60 years. This long-term view contrasts with many renewable energy studies that focus only on operation, missing the bigger picture.
In Iceland’s case, smart design and careful operation resulted in:
- Fast energy payback times (as little as 0.15 years for Búrfell II)
- Well-documented reservoir emissions (a rarity in global hydropower LCA)
- Evidence that older hydropower sites can keep performing cleanly for generations
Not All Water Is Equal
Interestingly, while tropical hydropower reservoirs can emit large amounts of methane due to lush biomass, Iceland’s cold reservoirs release less — though volcanic soils, rich in carbon, still add complexity. The researchers took a conservative approach, using gross rather than net emissions, to ensure transparency and caution.
They also highlighted the need for ongoing measurement of reservoir emissions — not just assumptions — and encouraged other countries to do the same using tools like the G-Res model, which accounts for land-use changes and natural emissions.
The Big Lesson: Build Smarter, Not Just Bigger
The cleanest hydropower station in the study wasn’t the biggest — it was Búrfell II, an extension to an older plant that re-used infrastructure and flooded very little new land. That approach resulted in the lowest emissions per kilowatt hour and the highest energy return.
It’s a blueprint worth following: upgrade existing plants, choose sites with low ecological disturbance, and plan with 100 years in mind, not ten.
For Canada, Norway, and other northern nations with hydro heritage, this could be a turning point. Instead of a rush to build new mega-dams, the future might lie in refining what already exists — and holding it to the highest environmental standards.
Source
Life cycle assessment of hydropower utilization in Iceland as a driving force for climate strategy and decarbonization, The International Journal of Life Cycle Assessment, 2025-02-24
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