Bus company Arriva has spent £2m on a fleet buses which will be powered by landfill-produced gas.
The investment will see the introduction of 21 gas engine buses after a successful trial of the technology in the North West this year.
The gas buses will enter service at the start of 2013.
Mike Cooper, managing director of Arriva UK Bus, said: "As one of the largest bus companies in the UK we are committed to leading the way when it comes to using technology to deliver solid benefits to our customers, the environment and our stakeholders.
"The buses have been specially designed for the UK market and, as they run on Bio-gas, provide a carbon neutral solution to the environmental challenges we face as a transport provider in the 21st century.
"The 21 new gas buses and our order of 153 hybrid vehicles is only one element of our strategy for improving our environmental impact.
"We have also invested in technological solutions to improve driver efficiency, training to raise awareness amongst staff, and created an upgraded roll-out plan to improve the energy usage of our depots across the UK."
Arriva have already used the new type of vehicle in Scandinavia and the Netherlands, where the company also operates.