Pond scum could be used to feed the world if it is used as a protein substitute for meat and eggs in meals, a Cambridge University professor has said.

While spirulina and chlorella, which are micro-algaes that form on top of water, are well known to health fanatics and have been eaten in space by Nasa astronauts, scientists hope they could become more mainstream in the future.

This is because they can be grown in urban environments and do not require high-quality agricultural land to grow, so could feed a growing population, especially if climate change renders some farmland unusable.

The small algae particles contain iron, B vitamins and protein along with other vitamins and minerals commonly found in meat, fish, eggs and dairy. The versatile powder can also be used as a supplement in bread, and instead of eggs in cakes and other baked goods.

Some chefs are even trying to turn it into fake "meat" - IKEA has commissioned Danish chef Simon Perez to make a version of their meatballs out of spirulina. He said he has managed to make it "taste the same" as meat, but that he is still working on the texture.

However, nutritionists have warned that as of yet, some of the nutrients are not bio-available, meaning that the body finds it more difficult to absorb than a non-vegan alternative.