Welcome back: The moments before the blackout in Spain and Portugal earlier this week were a window into Europe’s energy future, dominated by emissions-free but fluctuating generation. Spain’s electrical grid was humming with solar power—nearly 60% of total generation—on a largely cloudless day. Wind turbines provided another 9%. Wind and solar were so abundant that electricity prices were pushed into negative territory.

European Union economies have been investing heavily in both technologies, aiming to generate 69% of the bloc’s power from renewables by 2030. But grids running on high levels of solar and wind face technical challenges that grid operators are still figuring out how to manage. One of them could involve something called inertia. See below for the full story.

Meanwhile, the U.S. National Oceanic and Atmospheric Administration has faced a wave of staff cuts under the Trump administration and is still awaiting confirmation of Trump's nominee to lead the agency, Neil Jacobs.

But in a possible indication of things to come, the agency received an application yesterday from deep-sea miner The Metals Company to harvest minerals from the ocean floor. It is likely to be approved. Erik Noble, NOAA’s principal deputy assistant secretary of commerce for oceans and atmosphere, who was appointed by Trump in January, said last week: “The United States will lead the world in deep sea mineral extraction, and NOAA is the tip of the spear."

Finally, a startup that designed a mobile carbon-capture system for the trucking industry—using a device fitted to tailpipes—is moving on to the railroads. A freight locomotive burns up to 5,000 gallons of diesel before refueling. That's enough to generate 56 tons of carbon dioxide. Remora’s system would be loaded onto a tender car between the locomotive and the rest of the train. But carbon capture for transportation is complicated.

Read on for more on all these stories and other sustainability news.

The widespread power outage in Spain and Portugal this week forced authorities to confront an unprecedented event: the first mass electrical blackout on a grid largely powered by wind and solar energy.

Spanish officials said yesterday that they still didn’t know what caused the powercut, which left much of the Iberian peninsula without electricity for hours and disrupted everything from factories and trains to ATMs, the WSJ's Matthew Dalton and Ed Ballard report.

However, one issue they are looking at is the loss of so-called inertia in turbines. Conventional power generation turbines take a while to stop spinning, buying time to balance electricity supply and demand if something goes wrong. If a solar plant goes offline, output goes to zero instantly.

With less inertia, “imbalances must be corrected more quickly,” said David Brayshaw, professor of climate science and energy meteorology at the University of Reading in the United Kingdom. “Outage events, when they occur, are likely to become more significant and widespread,” he added.

Spanish grid operator Red Eléctrica hasn’t determined exactly what caused the outage but said it was possible that renewables were the cause. It has ruled out a cyberattack. For now, power supplies are largely back to normal.

• Renewables, and Good Luck, Prop Up Power Grid in Extreme Heat
• Five Ways to Disaster-Proof the Energy Grid
• Electricity That Costs Nothing—or Even Less?

Canadian deep-sea miner The Metals Company has asked NOAA for permission to harvest critical minerals from the ocean floor, under a new inititaive from White House. The seabed elements are considered vital for the energy transition, automotive and defense industries.

The move by the company follows President Trump’s executive order last week instructing the U.S. to gather and process minerals from the seabed in an effort to bolster infrastructure, advanced military energy systems and manufacturing, WSJ Pro Sustainable Business's Clara Hudson reports.

TMC’s U.S. subsidiary filed two exploration licenses and one commercial recovery permit to NOAA. TMC said the areas it wants to explore contain about 15.5 million metric tons of nickel, 12.8 million metric tons of copper, 2 million metric tons of cobalt and 345 million metric tons of manganese. Such minerals are used in everything from smartphones to medical devices.

Environmental groups are challenging TMC’s move. “Given that we have better maps of Mars than the deep-sea floor, we should all be concerned about this mad rush to allow a foreign company to exploit an environment we know little about,” said Katie Matthews of conservation charity Oceana.

• Deep Sea Miner Eyes U.S. Path for Minerals Production
• A Miner Goes Bust, Another Goes Solo as Progress on Seabed Code Stalls
• From the Deep Sea to D.C.—How China Fears Have Put Ocean-Floor Mining on Washington’s Radar

Startup Remora recently bought a 4,400-horsepower locomotive. The company plans to use the 1994 General Electric unit, which will be delivered this week to a parking lot in the Detroit suburbs via a new rail spur, to test its mobile carbon-capture technology for rail use.

Remora’s technology is designed to extract CO2 from the exhaust of diesel freight train locomotives and semi trucks, then purify and liquefy the greenhouse gas on board. It plans to sell the CO2, sharing the revenue with its transportation partners, WSJ Pro's Yuliya Chernova writes.

The goal is to help decarbonize the freight industry, a major contributor to carbon emissions, and the technology has drawn interest from railroad companies and trucking operators that will test Remora’s systems.

Despite the Trump administration’s move to reverse climate-change rules, demand for sustainable transportation technologies remains. Remora has signed technology evaluation agreements with railroad companies including Union Pacific, Norfolk Southern and Pacific Harbor Lines, as well as trucking operators DHL, Ryder and others.

• Truck Operators to Test Startup’s Onboard Carbon-Capture System
• The Next Big Thing in Carbon Capture? Trash.
• What Is the Future for Carbon Capture Technology?

Tell me what you think: Send me your feedback and suggestions at perry.cleveland-peck@wsj.com or reply to any newsletter. If you were forwarded this newsletter, you can sign up here.

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WSJ Pro Sustainable Business gives you an inside look at how companies are tackling sustainability. Send comments to bureau chief Perry Cleveland-Peck at perry.cleveland-peck@wsj.com and reporters Clara Hudson at clara.hudson@wsj.com and Yusuf Khan at yusuf.khan@wsj.com. Follow us on LinkedIn at wsjperry, clara-hudson and yusuf_khan.