Illustration: Matt Kenyon

It sounds like a miracle, but no great technological leaps were required. In a commercial lab on the outskirts of Helsinki, I watched scientists turn water into food. Through a porthole in a metal tank, I could see a yellow froth churning. It’s a primordial soup of bacteria, taken from the soil and multiplied in the laboratory, using hydrogen extracted from water as its energy source. When the froth was siphoned through a tangle of pipes and squirted on to heated rollers, it turned into a rich yellow flour.