Burning material during specialised training has also been left out of the brigade's CO2 figures.

BBC: Highlands and Islands brigade aims to cut CO2 emissions

The material that is burning up in Earth's atmosphere during the Quadrantids likely comes from a comet that broke into fragments centuries ago, NASA says.

CNN: Meteor shower will light up night sky for just a few hours

One of the most notable innovations: the development of a new catalyst material to purify exhaust from diesel or other lean-burning engines.

FORBES: GM: The Big Green Patent Machine

Carbon dioxide, the result of burning fuel, is, together with water and sunlight, the raw material of photosynthesis.

ECONOMIST: Horticulture