As strange as it might sound, trees eat CO - then they turn it into wood and (very importantly) oxygen.

As trees breathe, feed and grow, they trap carbon at rates and
levels that can be scientifically estimated. Likewise, estimates of the C0 emissions produced by trade, industry and manufacture can also be made. The next step is to calculate how much new forest it would take (plus how long that forest would need to stay in the ground) to 'sink' those emissions, i.e. lock up the harmful carbon but give back the oxygen.

This being an inexact science, it is vital to err on the side of safety. Our calculation model (see right) provides a safety margin so generous that three times the targeted amount of carbon can, in practice, be sequestered. That extra amount is forever untradable, held as insurance against the risks of destruction or slow growth. It's just a gift to the environment!

To 'offset' a thing means to compensate for its negative impact. Ideally, there should be no such thing as offsets of any kind because we shouldn't be churning out so much CO in the first place - which is why a lot of extra money (and CO itself!) is currently being released in the quest for renewables and cleaner energy sources. But progress is slow: e.g. protection of the world's rain forests (whose decimation accounts for 20% of global CO ) is on many agendas - yet the rain forests continue to fall at a sickening rate.

Alhough not a 'quick fix', the creation of additional woodlands specifically to act as carbon sinks is an antidote with many ecological fringe benefits. Forestry schemes like ours, which follow Kyoto's 'additionality' principle, make a real contribution towards locking in the world's unavoidable CO . But genuine carbon woodlands must be distinguished from poor quality, opportunistic schemes. To this end the UK Forestry Commission has developed a quality assurance standard by which projects can be independently verified - this (the Woodland Carbon Code) will be published in draft form in July, 2010.