Geological carbon capture & storage
Given the exorbitant costs of GEO-CCS solutions like direct-air capture, Experts in the field believe that money is much better spent on renewables (wind, water, solar) that prevent the CO2 and non-CO2 air pollutants from fossil-carbon combustion from being released in the first place.
Until we stop burning fossil carbon and have excess renewable energy, and direct-air capture costs drop to reasonable levels, GEO-CCS will remain an inefficient and impractical solution for sequestering atmospheric CO2.
How much carbon do we need to sequester?
Even if we stop burning fossil carbon we will still be adding about 27% of our current emissions (14.9 gigatonnes of CO2eq) into the atmosphere each year.
A practical goal would be to sequester at least 20 gigatonnes of CO2eq/year to not only capture the equivalent emissions we cannot avoid but also to start drawing down our atmospheric CO2 levels back below 350 PPM.
Is BIO-CCS a pipe dream?
With a growing population and the world’s tropical forests being cleared each year for agricultural land to feed the world, it seems unlikely that we can find the land to sequester 20 gigatonnes/year of CO2 by planting trees. Or is it?
The land required to produce 1 kilogram of protein from beef is 14 times greater than the land required to produce 1 kilogram of equivalent protein from beans, corn, or potatoes. With nearly 60% or 3.3 billion hectares of the world’s agricultural land devoted to raising beef, we could produce the same amount of protein from plant sources using only 260 million hectares of land, a 93% reduction in land area.
Sources: WRI, GlobAgri model (land use and greenhouse gas emissions), authors’ calculations from Mekonnen and Hoekstra (2011, 2012) (freshwater consumption), and Waite et al. (2014) (Farmed fish freshwater consumption).
How much land can we find?
If we were to substitute land-inefficient food sources, such as cattle, with efficient, plant-based alternatives — ideally using regenerative, no-till, and agroforestry practices — we would free up an area of land equal to the entire continent of Africa (over 3 billion hectares). This land could than be put to work performing other services, like farming carbon out of the atmosphere by growing trees.
Although much of this land wouldn’t be suitable for trees, a recent study released by the Crowther lab in Switzerland has indicated that up to 1.8 billion hectares of land, much of it coming from existing pasture lands, could be forested.
Carbon farming solves many of the world’s problems
Both afforestation and reforestation of cattle pasture lands will not only relieve logging pressure on existing natural forests which themselves are important carbon sinks and harbor much of the world’s terrestrial biodiversity, they would also provide the raw materials to supply a growing trend away from the use of CO2-intensive steel and concrete in building construction in favor of wood-based alternatives like laminated timber.
A Pathway to Reversing
The Target: 350 PPM
A safe level of atmospheric CO2 to avert runaway global warming is below 350 parts per million (PPM) (Hansel et al, 2008). Currently we are around 410 PPM. Carbon sequestration is therefore vital for returning atmospheric CO2 back down to safe levels.
Biological carbon capture & storage: Carbon Farming
All green growing plants sequester carbon from the atmosphere by storing it in their roots, stems, and leaves. Unlike GEO-CCS solutions, storing carbon in plants require only sunlight, water and green leaves.
Since BIO-CCS only stores carbon, (unlike GEO-CCS solutions like direct-air capture that stores the much bulkier CO2 molecule), the oxygen atoms of CO2 are returned to the atmosphere and help reverse declining global oxygen levels. BIO-CCS, or more specifically the planting of trees, is a very inexpensive option for sequestering carbon. The drawback of using plants to sequester CO2 is that they require space and lots of it.
How much land do we need?
Experts estimate afforestation of land in the tropics could sequester 25 tonnes CO2/hectare per year. Using these metrics, to sequester 20 gigatonnes per year would require the planting of 800 million hectares of land, an area the size of Australia and New Guinea.
We have the land, we just need to use it better.
The plight of our tropical forests
Since 1950, we have lost approximately 50% (7.5 billion hectares) of our tropical forests, and scientists estimate that number will increase to 80% by 2030 unless significant action is taken to stop deforestation. More than 80% of deforestation of tropical forests has been for agriculture, with a significant amount being to support livestock. In the Amazon alone, 91% of the 700 million hectares of land deforested since 1970 has been for livestock pasture. By converting this pasture land in the Amazon back to forests, potentially 15.9 billion tonnes of CO2eq/year or 29% of our current annual GHG emissions could be sequestered.
"What blows my mind is the scale. I thought [forest] restoration would be in the top 10, but it is overwhelmingly more powerful than all of the other climate change solutions proposed."
Swiss university ETH Zürich, July 2019
Drastically improving the efficiency of how much land is used to produce our protein and calories by switching to plant-based or more land-efficient animal sources, will also make it much easier to sustainably produce enough food to feed the world’s growing population.
By reducing our reliance on animals for food, we also help address another global threat: the spread of zoonotic pathogens (eg. Coronoviruses like SARS and COVID-19, AIDS, Ebola, Salmonellosis etc.).
According to the FAO, "Seventy percent of the new diseases that have emerged in humans over recent decades are of animal origin and, in part, directly related to the human quest for more animal-sourced food."