It's no secret that climate change is one of the biggest challenges facing the world today. In the Global Risks Report 2016, failure to mitigate the effects of climate change - as well as related risks such as water crises, food security and extreme weather events - dominated the list of major threats.

This is why a central tenet of the landmark Paris climate agreement, hammered out last December by representatives from 195 countries and effective as of 4 November this year, is to keep global temperature increases well below 2C and if possible, below 1.5C - something that can only be achieved through a significant reduction in the emission of greenhouse gases.

Greenhouse gas emissions trap heat and make the planet warmer, and the largest source of these is, of course, the burning of fossil fuels for electricity, heat and transportation. This is spewing an ever increasing amount of pollution into the air we breathe. As a result, an estimated 92% of the world’s population lives in areas where air pollution exceeds safety limits, according to the World Health Organization (WHO), causing millions of deaths a year and costing the global economy billions of dollars in lost labour income.

As of November 2016, 113 countries had ratified the Paris Agreement, showing that a concerted global effort to avert environmental catastrophe is being made. Governments aren't the only ones taking action to tackle air pollution, however. And as well as cutting emissions, there are a number of innovators, entrepreneurs and even artists who are hoovering up this CO2 and turning it into something that we can actually use. Here are a few of the technologies that could help to clean up our air for good.

Turning smog into diamonds

Smog is grimy, suffocating and unpleasant on the eye, but Dutch artist Dan Roosegaarde has come up with a way of turning it into a thing of beauty.

“It started with a dream,” he said at the World Economic Forum’s Annual Meeting of the New Champions. “The dream of clean air for everyone.” Staring out of a hotel window in Beijing (the city we often associate with smoggy skylines, though it is not the world's most polluted), Roosegaarde came up with the idea for the Smog Free Project.

How does it work? First of all, seven-metre-tall towers suck up polluted air and clean it at the nano-level. The clean air is then released back into parks and playgrounds, which Roosegaarde claims are now 70-75% fresher than the rest of the city.

The next step of the process involves turning the leftover carbon into precious jewels. Thirty-two percent of Beijing’s smog is carbon, which under 30 minutes of pressure can be turned into diamonds. The proceeds from the sale of this jewellery will be put towards the installation of more towers, Roosegaarde said in China.

Like plastic, but better

Plastic is one of the most world's most destructive materials. It's the workhorse of the modern economy, used in the manufacture of numerous products - but the fact that it's near indestructible means that it's devastating to our environment. Put simply, it's incredibly hard to make plastic go away. A study undertaken by the World Economic Forum, the Ellen MacArthur Foundation and McKinsey and Company states that only 14% of global plastic packaging is collected for recycling and only 2% is reused as packaging.

Meanwhile, a full 32% of the 78 million tons of plastic packaging produced annually is left to flow into our oceans; the equivalent of pouring one garbage truck of plastic into the ocean every minute. If we carry on as usual, this is expected to increase to two per minute by 2030 and four per minute by 2050.

We must find greener, cheaper alternatives, and Mark Herrema, CEO of Newlight Technologies, may have come up with one. His product, AirCarbon, is 40% air and 60% greenhouse gas. "No oil. No fossil fuels. Just air and captured carbon emissions that would otherwise become part of the air, combined," he wrote in this recent post for our blog.

Newlight has signed deals for £74 billion worth of AirCarbon in the last 15 months, and companies like IKEA have taken out licences to produce the material themselves. AirCarbon is biodegradable, as strong as plastic, and can be melted and formed into shapes. Most importantly, it moves oil out of our products and reduces the amount of carbon in our air.

From pollution to art

As well as turning pollution into materials with practical applications, researchers have also been looking into how to turn grotty, carbon-rich soot into art supplies. Graviky-labs, and India based spin-off from the MIT Media Lab, has developed a way to capture air pollution and make art supplies such as ink, pens and paints.

The product, Air Ink, is made from emissions captured by a cylindrical device attached to car tailpipes. The carbon from the pollution is then mixed with oils and water to make art supplies. The company claims that it takes as little as 30 minutes for the device to capture enough carbon to fill a pen. Anirudh Sharma, one of Graviky Labs' founders, claims he got the idea for the product when he noticed pollution stains on his clothes.

India has a big problem with air pollution. Thirteen of the top 20 most polluted cities in the world, according a World Health Organization (WHO) report from 2013, are in India. Recent satellite images from NASA, meanwhile, show levels of PM2.5 particles at 128 in New Delhi, compared to 81 in Beijing and 81 in Washington DC.

India, the world's fourth largest emitter, formally signed up to the Paris Agreement in October 2016, a move that was hailed as a major milestone for the deal.

Image: Greenpeace/NASA

Turning carbon dioxide back into fuel

Earlier this year, we hit the highest levels of atmospheric CO2 in 4 million years, moving past the point where we'll ever be able to return to 'safe' levels again. With all this surplus carbon dioxide floating around in our atmosphere, wouldn't it be great if we could turn it back into fuel?

Scientists at the US Department of Energy’s Oak Ridge National Laboratory accidentally discovered a way to do just that, using complex nanotechnology techniques to turn the CO2 into ethanol.

Image: IEA

Dr Adam Rondinone, lead author of a paper published in the journal ChemistrySelect, said: “We’re taking carbon dioxide, a waste product of combustion, and we’re pushing that combustion reaction backwards with very high selectivity to a useful fuel.

“You can use it [ethanol] in the current vehicle fleet, right now, with no modifications. Carbon dioxide is a problem right now. If we can use it, then we’re preventing it from going into the atmosphere.”

The team of researchers made a catalyst from carbon, copper and nitrogen and then applied an electric current. “We discovered somewhat by accident that this material worked,” Dr Rondinone said. “Ethanol was a surprise. It’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.”

The team is now developing the technique further and looking into practical uses for the technology, such as storing excess electricity generated by renewable energy sources.

When the air is so bad, you can turn it into bricks

Last December, a Chinese performance artist's project went viral after he turned Beijing's polluted air into a brick. The artist, who called himself 'Nut Brother', walked around China's capital for 100 days with an industrial-sized vacuum cleaner trailing behind him.

Hoovering up the particles that make up Beijing's polluted air, Brother Nut then mixed this 'dust' with clay and turned it into a brick.

The artist said he was trying to make a powerful statement about the dangers of air pollution, rather than coming up with a product that could be marketed as a practical solution to climate change.

"Air pollution is a problem faced by everybody. It is our right to breathe in fresh air, and right now, we're being deprived of that right," he said.

Image: Reuters