Body heat

For years, scientists have been experimenting with body heat as a source of energy. While wearable tech devices that directly convert it into electricity are currently in the works, a train station in Sweden is already harnessing the warmth generated by thousands of commuters.

Real estate company Jernhusen engineered Stockholm Central Station to channel the mass production of body heat to warm another building just across the road.

While harvesting body heat to keep a building toasty isn't a new idea, this is the first time it's been successfully transferred from one building to another. It's a long-term sustainable solution, which relies on a surprisingly simple low-grade waste heat source.

Turning CO2 into stone

Figuring out how to limit our production of carbon dioxide (CO2) has proved one of the greatest challenges of the 21st century. What if we could somehow capture it and turn it into stone? Sounds like a fantasy, but that's exactly what researchers in Iceland have been doing.

Hellisheidi, one of the largest geothermal power facilities in the world, pumps volcanically heated water to run turbines that produce electricity. But because this process releases CO2, the team tried pumping it back into the volcanic rock beneath the surface of the earth. There, it underwent a fast-tracked natural process of reacting with basalt to form carbonate minerals.

The entire transformation from gas to solid took two years. Previous carbon capture projects had only managed to store the CO2 in gas form, raising concerns about potential leakage and maintenance costs. But more recently researchers from RMIT University in Melbourne, Australia have taken the process a step further, using liquid metals to transform CO2 back into solid coal. 

Read more: Carbon capture: Expensive, risky — and indispensable?

Dance power

As we become increasingly aware of incorporating sustainability into all aspects of our lives, it might not surprise you to learn that 'eco-clubbing' is a thing. Back in 2005, two Dutch engineers invented the Sustainable Dance Floor, which essentially converts the kinetic energy generated by dancing into electricity — or piezoelectricity to be exact, which means energy resulting from pressure and latent heat.

When dancers make the floor bounce, springs installed underneath it convert the vertical movement into a rotational one, thereby generating electricity. Each step can generate anywhere between two and 20 joules of energy, which is enough to power LED lights in the floor, or other elements of the club such as sound or lighting.  A number of clubs around the world are now experimenting with this development to give their sustainability-minded patrons an eco-friendly clubbing experience. But the technology isn't limited to the dance floor.

Since 2009, all electronic signs at a railway station in Tokyo have been powered by kinetic energy generated by people walking on floor tiles installed at ticket gates. And the floodlights on a football pitch in Rio de Janeiro are kept on with the help of players' feet as they run across the turf. The takeaway? Don't underestimate the power of footsteps.

Read more: Dancing to do your bit

Coffee waste

Our love of coffee harms the environment far more than most people realize. The process of turning the fruit into the final product — of which we globally consume approximately 9.5 million tons a year — generates a massive amount of liquid waste.

Now, for the first time, scientists have figured out how to change this waste into electricity. They've developed a special fuel cell — a device which produces energy through a chemical reaction — that uses microbes to effectively eat the waste matter and generate electricity in the process. This technology could be used to help farmers in developing countries produce a more sustainable product.

Coffee waste can also be used as a biofuel. London based tech firm bio-bean currently sources raw waste from hundreds of cafes, offices and coffee factories around the UK and extracts oil from it. That, in turn can be made into commercially available 'coffee logs' that are used to heat buildings, or even liquid fuel which is already helping to power London's iconic double-decker buses.

Algae fuel

Another unlikely biofuel which could help save the planet comes from algae. Certain types contain natural oils which can be used as replacements for diesel, gasoline and even jet fuel. Like fossil fuel, this ocean alternative releases CO2 when burnt.

The difference, however, is that it remains carbon neutral. How? Because the carbon has only just been absorbed —via photosynthesis — at the time it's emitted, CO2 levels don't actually increase. 

After decades of research, algae fuel technology is finally moving out of the lab with companies starting to  look towards commercial production. While proponents are optimistic that algae fuel may be exactly what we're looking for, critics warn that it's still far from a perfect solution because the entire process is expensive and will require large amounts of land and water