Agence France-Presse: Humans and farm animals were known to emit harmful greenhouse gases through digestion, but German researchers said Tuesday that aquatic worms and bugs are also culprits, releasing laughing gas. Scientists at the Max Planck Institut and Denmark’s Aarhus University found that mussels, freshwater snails and other underwater creatures release nitrous oxide — laughing gas — when nitrate is present in water. “There’s nitrate in water that has been polluted by humans, so the more we …