A new wave of bartenders are championing zero-waste techniques in a global movement known as "closed-loop" cocktails. Focused on recycling ingredients, the idea is to ensure an eco-friendly drinking experience. It's part of a broader concept known as "garden-to-glass," which emphasizes produce-driven beverages that boast little food mileage — similar to the restaurant industry's "farm-to-table" approach.

Operation Dagger is Asia's leading voice on the matter. Ranked sixth on "Asia's 50 Best Bars 2017," the Singapore-based venue ensures ingredients are used to their full potential, whether it's replacing plastic straws with vanilla pods or creating bottle labels from recycled receipts. "The idea of closed loop for me is an ingredient that doesn't just have a beginning and an end," said head bartender and owner Luke Whearty, who previously ran a bar in Cape Town called Outrage of Modesty. "If one element of an ingredient is used for a drink, we'll use a different element for something else, kind of like how a chef works with prime cuts and uses secondary cuts for another dish."

Operation Dagger's famed 'Egg' cocktail, which blends salted egg yolk, rum, vanilla and caramel Operation Dagger

Take lemons as an example. Bars juice the fruit and often throw away the husk, but at Operation Dagger, the still-flavorful husk is used for a house-made limoncello before being composted. Eggs are another commonly squandered item, Whearty pointed out. Egg whites are popular in cocktails but the yolk is typically chucked, so Operation Dagger sought to highlight the yolk in its acclaimed drink that's aptly called The Egg. Yolk is cured with rum, vanilla and salted egg yolk — a popular food trend in Singapore — before being smoked in a jar with hay and star anise. The dimly-lit bar also makes wine with natural ferments, opting for cabbages, figs, beetroot, coconuts and carrots instead of traditional grapes. Meanwhile, beer drinkers can go for a 10-day fermented brew with heritage tomatoes, hops and malt. Drink ingredients are also turned into snacks. One dish is broccolini served with a fortified macadamia cream — the by-product of distilled roasted macadamia.

Operation Dagger's Orange Wine, consisting of seven-day day house fermented orange, carrot, rockmelon, orange blossom and honey. Operation Dagger