On Carbon Emissions, No Contest Between Wind Farms And Gas

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Fans of natural gas have been leaning on carbon-capturing technology to reduce emissions from power plants, but their grip on the electricity grid is dimming as the cost of renewable energy keeps dropping. In the latest blow against natural gas, a new study confirms that wind farms offset their own carbon emissions in well under two years, instead of burning fossil fuel for decades.

Wind Farms Offset Their Own Carbon Emissions

There being no such thing as a free lunch, wind farms are not entirely carbon free. Turbine manufacturing has been cited a the chief source of greenhouse gas emissions related to wind farms. Emissions also come from site preparation, transportation, and the construction of transmission lines and other infrastructure.

The question is whether or not wind farms can efficiently offset their own emissions compared to natural gas power plants. If emissions are nearly comparable, then gas stakeholders can make a stronger case for carbon capture.

The short answer is no. Also, the long answer is no. In the latest evidence that wind farms win the low carbon race by a long shot, a team of researchers took a deep dive into the 41-turbine Harapaki wind farm under construction in New Zealand.

The researchers concluded that the overall carbon footprint of the wind farm works out to a “greenhouse gas payback time” of just 1.5 to 1.7 years compared to a natural gas power plant, over a lifetime of 30 years.

Considering that the researchers compared the wind farm to a high efficiency, combined cycle gas power plant, that’s pretty impressive. The researchers surmise that their results can be generally replicated on wind farms around the world.

While the Harapaki study confirms previous findings of a rapid carbon payback, the researchers also point out that much of the analyses undertaken in prior years involves smaller wind turbines of up to 2.5 megawatts. The turbines at Harapaki are 4.3-megwatt turbines manufactured by Vestas.

What About Wind Turbine Recycling?

Despite the wide gap between wind farms and gas power plants in terms of carbon emissions, there is always room for improvement. The Harapaki study authors point out that end-of-life treatment is an important consideration.

“As the deployment of wind energy rises, the amount of generated turbine waste increases,” the researchers note. “Thus, ensuring sustainable end-of-life management is crucial. While recycling metals and rare earth elements is feasible, blades, on the other hand, are made of materials that are difficult to recycle, often leading to their disposal in landfills or incineration.”

The researchers take note of the technology challenges that lie ahead for turbine blade recycling. They also observe that resolving these challenges will have a significant impact on carbon emissions from wind farms.

For example, the carbon payback estimate of 1.5–1.7 years for the Harapaki project reflects an estimated carbon footprint of 10.8 grams of CO2 equivalent per kilowatt-hour, assuming the turbine blades are simply dumped in a landfill after decommissioning. The researchers estimate that the carbon footprint drops to 9.7 grams of CO2 equivalent if the blades are recycled.

The details of that Hapakari study are available online at the Journal of the Royal Society of New Zealand under the title, “Developing onshore wind farms in Aotearoa New Zealand: carbon and energy footprints.”

Wind Farms & The Green Steel Connection

Recycling or not, other studies have indicated that carbon capture technology has a lot of catching up to do if it’s going to bring natural gas power plant emissions down anywhere close to wind farms. The US Department of Energy cites a study from 2012 that estimates lifecycle emissions from wind energy at 11 grams of CO2 equivalent. The 2012 study also yielded CO2 equivalent of 465 grams for natural gas, with coal coming in dead last at 980 grams.

As for trimming the carbon footprint of wind farms even farther, blade recycling is just one pathway. Stakeholders are also beginning to adopt low-carbon steel to manufacture turbine towers. On January 16, for example, the leading turbine maker Vestas announced a new low-carbon partnership with the steelmaker ArcelorMittal.

“The low-emission steel is produced using 100% steel scrab [sic; they mean scrap] which is melted in an electric arc furnace powered by 100% wind energy at the ArcelorMittal steel mill, Industeel Charleroi, in Belgium,” Vestas explains. The steel can be use for entire onshore wind turbine towers and the top section of offshore turbine towers.

Here in the US, the steelmaker Nucor has built its new plant in Kentucky around a green steel model, with an eye on supplying offshore wind turbines. As with the ArcelorMittal plant, the Kentucky plant deploys recycled steel and electric-arc furnaces. “Nucor claims that the greenhouse gas intensity of its steel is 1/5 the average for conventional steel making from raw materials in blast furnaces,” CleanTechnica noted when the plant opened last year.

Steel makers are also exploring green hydrogen to help decarbonize their industry. Though costs are higher, some investors apparently foresee a more competitive scenario in the future.

Better Blades For Low-Carbon Wind Farms

Onshore wind farms can also take advantage of a more flexible range of materials that can potentially impact the carbon footprint of manufacturing, since they don’t have to deal with saltwater, waves, and other offshore conditions.

For example, balsa wood is already in common use for manufacturing wind turbine blades. A startup in Germany has raised the bar with a first-of-its-kind blade made of laminated veneer lumber, designed for onshore wind farms.

The US Department of Energy is also eyeing plant-based resins to replace the fossil-derived epoxy binder used to manufacture turbine blades, with the aim of easing the road to recycling.

Another approach with the potential for reducing carbon emissions involves deploying equipment to manufacture wind turbines towers at wind farms, instead of transporting ready-built components from distant factories. Spiral welding and 3-D printing are in play. If you can spot any other examples, drop us a note in the comment thread.

As for carbon capture, gas power plants are not going away in the near future, but the writing is on the wall. Here in the US, the Environmental Protection Agency threw down the gauntlet in April when it issued carbon emissions rules that require carbon capture systems for new baseload gas power plants by 2032. For all the effort and expense, though, the requirement only sits at 90% capture.

New rules for existing gas power plants will be announced later this year, so hold on to your hats.

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Image (screenshot): The Harapaki wind farm in New Zealand is the subject of a lifecycle carbon emissions study (courtesy of Meridian Energy).