Far away from the super stadiums of Barcelona's Nou Camp and Wembley Stadium in London, lies The New Lawn, home to Forest Green Rovers (FGR). Officially recognized by governing body FIFA as the world's greenest soccer club. Located in the tiny town of Nailsworth in Gloucestershire, England, Forest Green plays in the fourth tier of English soccer and is the smallest club to ever play in the professional leagues. FGR is the world's only vegan soccer club after making the switch to a plant-based diet for all players, fans, staff and events two years ago. It is now been certified carbon neutral by the United Nations, after signing up to the UNFCCC Climate Neutral Now initiative.

GEOFF CADDICK/AFP/Getty Images

Forest Green chairman and founder of clean energy company Ecotricity, Dale Vince, told CNBC that sport is a good vehicle to carry the sustainability message. "Today 30 percent of Britain's energy comes from renewable energy already, that's increasing. Electric cars are on the verge of taking over the roads," said Vince. "Veganism is becoming a really popular thing. And this football club has all of those elements in it, and it's a great vehicle for getting the message out." There's clear, clean energy evidence all around the stadium with solar panels on top of the south stand roof and a system that means all rainwater that falls on the stands or on the pitch is recycled, to minimize the club's use of mains water. The club has electric car charging facilities at the stadium, to encourage fans to travel to games sustainably and even a robot gardener, known as "The Mobot," taking care of the world's only organic soccer field.

A general view of The New Lawn, home of Forest Green Rovers. Steve Parsons/PA Images via Getty Images