For companies strategizing the planting of forests to offset carbon emissions – as Eni is doing as previously covered in the Combustion Industry News – there has been good news in the form of research done at ETH Zürich. The team at the Crowther Lab has estimated that, worldwide, there are 1.7 billion hectares of treeless land on which a total of 1.2 trillion trees could grow, capturing 205 billion tonnes of carbon over 50-100 years. While the paper, published in Science, is reported to have estimated that the amount would be the equivalent of two-thirds anthropogenic emissions since the Industrial Revolution, a better estimate may be one-third. To look at it from a different perspective, at the present rate of emissions of around 50 Gt of emissions per year (from fossil fuel burning for electricity generation, transportation and industry, as well as land use changes), that 205 billion tonnes is equivalent to only around 4 years of present emissions, a very sobering realisation, and one that points to the need to rapidly decarbonise the global economy. In addition, as the world’s population grows, and food consumption patterns change, it is unlikely that all of the land estimated in the research will actually be available for planting. Still, the research is positive news, particularly as the researchers excluded any land currently used for crop production, as well as any urban area. (Grazing area was included, but the rate of planted was assumed to be low enough to maintain grazing activities.) Overall, 11% of Earth’s landmass could be (re)forested, according to the research, although other scientific criticism of the report has said that it does not account for carbon currently contained within the land in these areas to be planted, and that some trees would take more than 100 years to fully grow. There were also concerns for monocultures, although there was at the same time an acknowledgement that extensive tree planting could also be a global environmental boon in providing for more biodiversity. The researchers suggest that if done highly efficiently, each tree could cost US$0.30 (€0.27), making a total cost of US$360 billion (€321 billion), which, while being an enormous amount, would easily be the cheapest carbon removal means in the world, at only US$1.76/tonne of carbon (€1.57), around 50 times cheaper than what is currently suggested for direct air capture, and perhaps 20 times cheaper than current estimates for carbon capture and storage installations at industrial facilities. The Crowther Lab had previously estimated that around 10 billion trees are being lost each year at present.