A man walks into a supermarket , hands over a beer can and receives money back . This may seem contrary to the natural order -- but it 's all part of brewer Carlsberg 's sustainability drive . Central to this is Carlsberg 's use of Denmark 's reverse vending machines , run by Dansk Retursystem . There are 3,000 of these futuristic reverse vending machines dotted around Denmark , through which 3 million items are deposited every day . You put a can or bottle into the machine and it gives you a voucher or money back for your efforts . The number of packages returning through the system is astonishing : 90 % of cans designed for single use are recycled , and nearly 100 % of refillable bottles find their way back to Carlsberg . The brewing giant 's bottles and cans themselves are designed to be as sustainable as possible . To make packaging more environmentally friendly , `` the most obvious thing we can do is reduce the weight , '' said Simon Hoffmeyer Boas , CSR manager . Lighter products can lessen energy needed in the manufacturing process , and `` within the last 20 years the average weight of a glass bottle has been reduced by approximately 30 % , '' Hoffmeyer Boas said . The innovation makes the bottles cheaper to manufacture , alongside being better for the environment . `` For us sustainability , or CSR , is business , it 's not something that is detached , '' he said . From the barley to the bottle , every part of the process is scrutinized by the company 's research and development department to ensure it meets or beats sustainable targets . In the Carlsberg laboratory , where the pH scale was developed , new types of barley are developed . In 2010 the company introduced the Null Lox variety . Brigitte Skadhuge , director of applied research , told CNN that type of barley `` helps beer to stay fresh for a longer time than traditional beer . '' That gives beer a longer shelf life , reducing waste . The by-product of the spent grain also helps power the plant . The husk , the outer covering of the barley grain , is placed in a bi-fermentor which transforms the cellulose into methane gas . This gas provides 90 % of the thermal energy needed at the plant . Even the waste from the waste is put to good use -- the waste from the bio-fermentor is used as a natural fertiliser in the barley fields .
There are 3000 of reverse vending machines dotted around Denmark . Bottles and cans themselves are designed to be as sustainable as possible . 90 % of cans and 100 % of the refillable bottles are deposited in the machines .