© Licensed to London News Pictures.  17/03/2015. Bristol, UK.  The Number 2 powered by poo Bio-Bus, which is powered by biomethane gas from human and food waste, on show in Bristol's Broadmead shopping centre before starting next week on the Number 2 route from Cribbs Causeway to Stockwood. It emits 30% less CO2 than a standard diesel bus and produces virtually odour free emissions. Photo credit : Simon Chapman/LNP