TECH

Recycling for the energy transition: Fossil fuel infrastructure provides raw materials for sustainable energy production

To transition from fossil fuels to renewable energy sources, we need to build new infrastructure. Empa researchers show that obsolete fossil fuel infrastructure – such as coal mines, oil and gas platforms, fossil fuel power plants, and pipelines – can provide some of the raw materials needed for the energy transition. In particular, recycling copper and steel would make the energy transition more cost-effective and environmentally friendly.

Moving away from oil and gas and toward solar, wind, and hydro power: That is the energy transition. To stop global warming, we must shift our energy infrastructure toward renewable sources in the coming years. The large-scale construction of solar cells and wind turbines requires, among other things, minerals and metals. At the same time, the existing fossil fuel infrastructure is becoming obsolete. So, could we recycle parts of our old energy system to build the new one? Researchers from Empa’s Technology and Society laboratory investigated this question in a study.

Their study was conducted as part of the EU project CircEUlar and was published in the journal Nature Communications. The researchers analyzed the stocks of 22 different materials contained in today’s coal mines, oil and gas platforms, fossil fuel power plants, and large pipelines. “To understand the potential of this ‘urban mine,’ we first need to know what materials are available in it,” says Empa researcher Hauke Schlesier, the study’s lead author.

Two raw materials stood out: steel and copper. Both metals are present in large quantities in fossil fuel infrastructure – and are urgently needed for the energy transition. “Copper is used in transformers and cables, while steel is used for structural elements,” says Schlesier. According to the study, recycling fossil fuel infrastructure could cover the entire steel demand and about one-third of the copper demand for the energy transition. As fossil fuel infrastructure is phased out, these additional material streams would become available for recycling. According to the researchers’ calculations, the capacities of global recycling facilities would be sufficient to recover the copper and steel needed for the energy transition.

More economical and environmentally friendly...But does recycling steel and copper from fossil fuel infrastructure really make sense? The researchers' answer to the question is “yes.” The recycling processes for both metals are significantly more environmentally friendly than their primary extraction. “Steel production generates slag, particulate matter, and large amounts of carbon dioxide, while copper mines produce toxic waste,” says Schlesier. Recycling, on the other hand, primarily requires electricity: Steel is melted down in electric furnaces, while copper can be recovered through an electrochemical process.

From a macroeconomic perspective, repurposing existing steel and copper stocks is highly beneficial. The researchers emphasize that it is worthwhile to begin recycling as early as possible, as this results in the lowest follow-on costs. The primary extraction of raw materials causes environmental and health damage, which entails significant follow-up costs for society (so-called externalized costs). “By recycling steel and copper from fossil fuel infrastructure, we could save between four and eleven trillion U.S. dollars in externalized costs by 2050,” says Schlesier. What's more, recycling itself is no more expensive than the primary extraction of steel and copper and is therefore quite competitive. “In addition, up to two billion tons of CO2 equivalents can be avoided. That corresponds to about 50 years of Swiss emissions,” adds Schlesier.

The main challenge for recycling valuable raw materials from fossil fuel infrastructure is the lack of incentives. “For state-owned fossil fuel companies, reducing societal costs could provide an incentive to phase out fossil fuel infrastructure sooner. This is less likely to apply to privately owned energy companies,” explains Schlesier. “They usually have no economic interest in minimizing externalized costs.” Further targeted incentives from the government could help address this.

Benefits for the energy transition...The recycled steel and copper could then be used worldwide in solar panels, wind turbines, power lines, or electrolysers for hydrogen production. “A promising approach is to use recycled steel instead of aluminum in the mounting systems for solar panels,” says Empa researcher Harald Desing, who co-authored the study. This could reduce the carbon footprint of solar panels by about a third. The amount of steel in the fossil-fuel infrastructure would be sufficient to provide two to five times the amount needed to meet global climate targets for solar power systems.

Recycled steel and copper could also be used in wind turbines. This would likewise reduce the carbon footprint of wind turbines by about a third. If the recycled steel were used exclusively for the construction of wind turbines, it could cover the total steel demand required to meet climate targets through 2050. “It could also be used in power lines and electrolysers for hydrogen production,” says Schlesier. “The key point is that clean energy technologies must gradually replace fossil fuel infrastructure so that the embedded steel and copper can be reused.”

Repurposing fossil fuel infrastructure can save trillions of dollars in global social, economic, and environmental costs during the energy transition. Reusing existing assets accelerates decarbonization, prevents capital waste, and mitigates the impact of unemployment on communities dependent on traditional energy.

Reducing capital expenditure (CapEx):

Leveraging gas pipelines: Converting natural gas networks to transport green hydrogen.

Repurposing platforms: Transforming offshore oil structures into foundations for offshore wind energy.

Using depleted wells: Adapting deep oil wells to harness geothermal energy for residential and industrial use.

Existing electrical grids: Connecting solar farms to legacy coal substations to avoid the cost of new transmission lines.

Mitigating environmental and social liabilities:

Avoiding idle assets: Preventing trillions of dollars in physical infrastructure from becoming financial losses (stranded assets).

Preserving jobs: Transitioning refinery operators to roles in biofuel and hydrogen plants.

Carbon storage: Utilizing depleted oil reservoirs for CO₂ capture and storage (CCS) projects.

Revitalizing industrial sites: Converting decommissioned thermal power plants into battery energy storage system (BESS) hubs.

Key financial and technical challenges:

Material incompatibility: Hydrogen can embrittle the steel in old pipelines, necessitating expensive coatings.

Retrofitting costs: The initial investment to repurpose a structure can sometimes approach the cost of building a new one.

Geographic location: Legacy extraction sites do not always align with areas offering the best solar or wind potential.

Regulatory complexity: A lack of clear laws for transferring permits from fossil fuel operations to renewable energy projects.

Empa technology and society laboratory---www.efd.admin.ch