Scientists and architects in London are developing plastic 'curtains' that can be attached to any building and which contain live photosynthesising algae. Polluted air can be pumped in from the bottom of these curtains, it is then passed through the algae and oxygen is released from the top. The inventors say that each curtain has the same power to turn carbon dioxide into oxygen as a mature tree. 

It’s not something that perhaps offices or blocks of flats will go for as they're not the prettiest things in the world. But could this be an alternative way to 'green up' unsightly car parks or warehouses? The curtains would be perfect for those spaces where there is not the space, budget or manpower to maintain trees, gardens or a green wall.