You may have seen some of these balloons appear here and there, too: https://www.google.com/search?tbm=isch&q=Biogasanlage https://www.google.com/search?tbm=isc

You may have seen some of these balloons appear here and there, too: https://www.google.com/search?tbm=isch&q=Biogasanlage https://www.google.com/search?tbm=isch&q=Biogasanlage Having now read the wikipedia article, I see that my answer to my youngest daughter was much too simple. "Daddy, what's that?" "That white balloon next to the barn? It's full of cow fart. The cows in the barn fart, the farmer keeps the fart in the balloon and then burns it to make electricity when people need lots of electricity". According to Wikpedia it's a little more complex. But I like the simple version better. Whatever the source, it's gas the farmer can burn whenever the spot price for electricity is high.