Colloquium: Ning Zeng

To keep Earth safe from dangerous climate change, a large amount of CO2 will need to be removed from the atmosphere and stored away permanently, via negative emissions technology, for example, planting trees. But planting trees is not enough. The natural carbon cycle is in near balance. In an established forest, some trees absorb large quantity of CO2, but other trees die, decay and release carbon back into the atmosphere. The idea of Wood Harvesting and Storage (WHS) proposes management intervention by tree harvesting or waste wood collection, followed by secure storage in engineered structures called Wood Vault to prevent decomposition. Because the forest as a whole is still maintained and continues to absorb CO2, the net effect is to remove CO2 from the atmosphere. It is estimated that the potential for sustainable long-term carbon sequestration using WHS is 0.5-3 GtC/y (2-10 GtCO2/y), with the upper range being 1/4 of our current fossil fuel emission rate. Demo projects conducted so far show a durability of hundreds to thousands of years, and a cost of $30-100 per tonne of CO2 sequestered. Specific applications can have synergy with waste management, fire risk reduction, mine remediation, as well as extending the benefit of reforestation. The technique is low cost, distributed, easy to monitor, safe, creating green jobs, thus providing an option in the 'toolbox' of climate mitigation and adaptation strategies. The idea is now being put into practice commercially in the burgeoning industry of Carbon Dioxide Removal (CDR), while opening a new research subject.