Every holiday season, a giant Christmas tree stands in the center square of Kuressaare, a town of about 13,000 people on the densely-forested Estonian island of Saaremaa. Come January, that mighty spruce topples over and lands in the cocktails of drinkers from Romania to France. This second life is all part of a local distillery’s mission to transform Northern European Christmas trees into tonics. The eco-friendly project was started by Estonian couple Maarit Pöör and Tarmo Virki. Pöör, an art teacher, and Virki, a journalist and publicist, created Estonic Soda…