A bus that smells of coffee

Written by Qing LI， correspondent stationed abroad

Imagine that when you sit on a bus in the morning， drinking latte or caramel， the bus exhaust smells not of petrol but of the aroma of coffee， and that this bus is driven exactly by the coffee residue of latte or caramel.Do youthink it ever possible？ Actually it will not be long before such buses， using the coffee residue as fuel， travels through the streets of London.

Because of the great demand of human life and industries， more and more green gases like carbon dioxide are released into the atmosphere， resulting in global warming， which causes many bad consequences that we already know， such as the sharp decline of the number of glaciers， the rise of sea level， climate anomalies， land drought， wildfires and frequent super hurricanes. In the face of such plight， humans are also looking for alternatives to oil. Forexample，we try to turnsugar-sweetened corn and sugarcane into alcohol to make fuel for automobiles or use gas as fuel for automobiles. A British company called "Bio-bean" invented the so-called B20 "biodiesel" --extracting the coffee oil with the coffee residue processing technology， mixing it with otherester oil， and then mixing them with 20% of the proportion of the diesel fuel to produce fuel for automobiles.

Bio-bean estimated that Londoners would drink 20 million cups of coffee a day，which amounts to 500，000 tonsof coffee residue a year for the international metropolis， so that the raw materials for making coffee oil were plentiful. Its partner Shell Oil says the potential to extract coffee from coffee grounds is huge enough to meet the fuel needs of the country's 1/3 bus systems. So far， Bio-bean and major British coffee shops and coffee makers have been able to recycle about 50，000 tons of coffee residue a year and have distilled 6000 litres of coffee oil from discarded coffee grounds， an amount enough for a buss fuel for the whole year. Therefore， "biodiesel"not only reusesthe waste， but also reduces the partial dependence on oil and the emissions of toxic nitrogen oxides， which makes itvery green.

But the problem with biodiesel is also obvious. First of all， it is not entirely free of pollutionbecause it must also be mixed with the diesel. Secondly， in the process of making coffee oil， it will produce a kind of raw glycerin which is difficult to deal with and unrecyclable. It is reported that London has proposed to achieve zero public transport pollution in 2050， so let's wait and see how London will solve these two thorny problems！