Fancy a free kayak trip? As long as you pick up some trash, too, you can glide along rivers and canals in Denmark, Norway, Finland, Sweden, Japan and Germany, thanks to an idea born in Copenhagen. Called Green Kayak, people are kitted out with green boats and equipped with a large bucket and two litter pickers. They are also handed maps of the waterways, showing where protected birds or plants should be avoided. After each tour, their litter pickings are weighed and recorded. Germany is currently expanding the project which is established in Berlin, Hamburg, and Leipzig and is set to grow into…