During a protest outside the COP26 climate-change summit Friday, Greta Thunberg offered a strident refrain. “Change is not going to come from inside there,” the activist said outside the Glasgow meetings, decrying the “politicians and people in power pretending to take our futures seriously.”

“We say ‘No more blah, blah, blah,” she pronounced.

A casual observer could be forgiven for thinking Thunberg had a point — there has been, ironically, some hot air at the summit, despite some concrete actions, like the agreement by some 40 countries to stop funding new coal-fired projects and a separate pledge by nations to reduce methane emissions by 2030.

And it turns out many of the aspirations voiced at the conference are being enacted on the ground — by innovators and entrepreneurs. These are often small companies, academic researchers or even just individuals, putting together nifty inventions and crafty business plans that aim for less waste, more efficiency and all manner of climate-change mitigation.

Here are five calls from leaders — and the entrepreneurs far away from the halls of power who are quietly moving on them.

“We have the ability to invest in ourselves and build an equitable clean energy future.” — U.S. President Joe Biden.

When it comes to clean-energy innovation, a Massachusetts company, Form Media, is giving everyone else a run for their money. The firm, undergirded by research from MIT professor Donald Sadoway, is taking rust on a power grid and using it to store … renewable energy.

Essentially, it’s taking the oxidization process, normally not good for much but ruining your Saturday garage clean-up, and deploying it to store energy on power grids. It can do so, the company says, at just 10 percent the cost of a lithium-ion battery, the go-to method for such storage.

Nor is it just power plants. As a result of this grid overhaul, the idea is that anything we as consumers do electric in the new world — like, say, cars — will get a lot cleaner, running, from an environmental perspective, on what are ultimately long-lasting batteries.

On the matter of locomotion, few energy solutions are as ingeniously simple as that of Vinisha Umashankar, a 14-year-old from southern India. Her country has some 10 million “ironing carts,” in which itinerant vendors travel towns helping people iron clothes. Nearly all of them burn charcoal.

So she had the idea of tricking out these carts with solar panels, and now they can iron a lot more cleanly across a country that produces 7 percent of the world’s greenhouse gases. The idea is competing for the Earthshot, the new British prize that’s seen as a kind of Oscars for environmental entrepreneurship.

Umashankar told The Post last month she saw the idea as portable to other mobile businesses. “Soon, there may be solar veg-carts or ice-cream carts, you never know.”

“I have drawn great comfort and inspiration from the relentless enthusiasm of people of all ages — especially the young — in calling for everyone to play their part.” — Queen Elizabeth

Fitbit tracks steps, Noom tracks calories, SleepSpace tracks napfulness. The new trend is for consumers to try to take stock of their environmental impact, with a growing number of tools to help them.

MIT professor Jessica Trancik has come up with a carbon counter that measures with surprising (and disturbing) detail the carbon footprint of a car we own or soon might.

Two Polish researchers, Łucja Zaborowska and Julia Żuławińska, have devised a similar calculator for trees — plug it in and it will tell you how much oxygen it’s providing, a useful tool not just for professional planners but citizens looking to make decisions about where to live. “The ideal end-user(s) for this could be a single-family house owner or just people who want to make an impact on their communities and their health,” Żuławińska said in an email.

And there’s the food impact: the BBC and London search-engine company Verve have teamed up for a nifty tool that allows consumers to assess the impact of their diet on greenhouse-gas emissions.

“One of the really important aspects of addressing climate change is bringing everyone into the discussion,” Trancik told The Post in an interview.

She imagines all of these tools getting more sophisticated, with people who can afford to do so factoring in the carbon footprint of everything from commuting routes to where to live — a future in which environmental impact is as much a point of comparison as price and quality.

“There’s a lot of focus on climate refugees,” she says. “I think another wave will be climate emigres, and these tools can be very helpful.”

“The entire physical economy is totally implicated. Every material we make, every factory that exists in the world is involved in this.” — Bill Gates, to The Post.

Gates was describing the emissions that happen in a world of massive industrial production and the gases and waste that come from it.

Innovators have been finding some pretty novel ways to salvage them.

A United Kingdom firm, bio-bean, has been processing tens of thousands of pounds of waste from coffee grounds each year, including from the likes of Stansted Airport, and turning it into bio-fuel.

Startups have also been trying to eliminate waste at a common source of the problem: grocery stores. As much as 30 percent of all food at U.S. supermarkets winds up in the trash, and food waste accounts for 8 percent of greenhouse-gas emissions.

By using a more efficient, algorithm-driven ordering system, companies like the Seattle startup Shelf Engine want to ensure that stores never stock more than they can sell.

But for sheer novelty in this post-waste world, few companies may top Extract Energy. The Ontario startup uses an alloyed blend of nickel and titanium to convert heat waste — you know, the stuff that radiates from every appliance and power plant — into clean energy. It does this in a unique way: by allowing the metal to bend and return to its form.

The founder, Ibraheem Khan, got the idea when tinkering with metals and realized this bendability could function almost like a machine, storing and then expending the energy. He first tried it out with braces — his wife is a dentist — before transitioning it to bigger applications.

The idea is a kind of net-zero twofer: it makes something useful from the heat-waste emissions and also creates much cleaner energy than the fossil-fuel kind.

In an email to The Post, Khan said that if his company scales up fast enough he ultimately believes it could cut greenhouse-gas emissions by 5 billion tons.

That’s an extremely high number. But even if it didn’t get anywhere close to that total, Khan still stresses these are the kinds of innovations that the world needs to embrace.

“Some of the resolutions coming from COP26 require very aggressive transitions in order to meet climate goals,” he said. Instead, repurposing existing forms of waste made more sense. “What we find more exciting is the potential to tap into geothermal sources of heat and essentially create carbon free energy,” he wrote.

Of course, none of this is as innovative as running your Aston Martin on wine and cheese, as Prince Charles recently said he did. Maybe one day.

“Are we really going to leave Scotland without the resolve and the ambition that is sorely needed to save lives and to save our planet?” — Barbados prime minister Mia Mottley

When it comes to ambition, robot insects are pretty high on the scale.

We all know the problem if bees fade — without the creatures, whole chunks of the food chain collapse. Oranges, coffee, avocados and dozens of other crops all but go away. And bee health and species diversity are in dangerous decline.

The innovative plan has been to replace them with AI’s — little buzzing devices that lend themselves to all the puns you can drone on about. Over the past decade it’s been looked at by everyone from Washington State University to Walmart.

The Japanese have tried it; so have the Dutch. Most recently it’s been Israeli startups giving it a shot, with images sure to leave the Honey Nut Cheerio mascot shaken.

These devices all operate on a similar principle: that the pollination bees do naturally and humans do slowly can be done efficiently by pre-programmed micro-flying machines.

The question is whether they actually work: can they replace the population, and the pollination?

For that we turned to Marla Spivak, an entomologist at the University of Minnesota and a world expert on bees. Her answer? Not so fast.

It’s a problem of scale, she says. “Robot pollinators might be useful in greenhouse or high-tunnel situations, with a limited number of flowers in a confined area,” Spivak wrote in an email. “But on a large, outdoor scale; e.g., 1 million acres of almond flowers? No. “ Well, innovation can’t solve every problem.

“We, particularly countries with large green areas and re-greening potential as well as countries with vast seas that have the potential to contribute to carbon sequestration — we need support and contributions from developed countries.” — Joko Widodo, president of Indonesia

Widodo was making a plea that has been familiar from developing countries: more resources are needed. This is especially true after developed nations fell $20 billion short of a $100 billion commitment last year.

But it’s the two words in the middle of that passage — “carbon sequestration” — that are so key. Carbon sequestration, or storage, along with the other half of the equation, carbon capture, is one of the most innovative approaches to climate change. It’s also one of the most controversial.

Basically, the idea is to snatch carbon from the air, then stash it away. A plant in Iceland, run by the Swiss company Climeworks and backed by Microsoft, is capturing carbon and turning it into rock.

Meanwhile, Exxon said this week it wants to engage in carbon capture along the 53 mile-long Houston Ship Channel, along which millions of barrels of crude oil are processed, and is asking investors for $100 billion for the project. (It will spend about $3 billion itself.) The idea is to build a system that will capture and then transport by pipes all the carbon that’s produced by the industrial facilities along the channel to be buried under the Gulf of Mexico.

The International Energy Agency had said it’s “virtually impossible” to reach climate targets without using this tech; simply cutting getting to zero emissions by 2050 won’t undo the damage already out there. But critics say carbon capture is a slippery slope, and could encourage the very dangerous emissions that got us here in the first place.

And the tech may not even be a workable solution, they say. “The costs involved are prohibitive … There is also significant deployment time to consider,” said a report this year from researchers at the United Kingdom’s Tyndall Centre for Climate Change Research.

But carbon capture has the backing of some high-ranking U.S. government officials.

“I don’t think we can discount the capacity of any technology that exists now or will exist in the very near future that will help us reach our milepost by 2030 or 2040 on the way to a net-zero economy,” U.S. Agriculture Secretary Tom Vilsack said in an interview with The Post Friday when asked about the backlash.

Vilsack said he has been following a host of agricultural innovations beyond carbon capture, from more efficient forms of fertilizer to a Stanford-affiliated projectthat literally aims to capture lightning in a bottle by harnessing energy from thunderstorms.

“We have to do all of it. And we have to do all of it fast,” he said.