Cheap alternative to costly green tech
- Ivo Vegter
- 03 Jul 2017 10:02 (South Africa)
If you follow green technology, you may have noticed the unveiling of an urban “tree” which looks like an advertising screen covered in greenery. This “CityTree”, it is claimed, “cleans as much polluted air as a forest”. Perhaps you saw the launch of the world’s first commercial carbon capture plant, which “just started sucking CO2 out of the atmosphere to save us from climate change”.
This is good news, right? Science and technology to the rescue! Who doesn’t love that? It’s just that the numbers make no sense. At all.
Let’s start with the carbon capture plant, which began operating on 31 May 2017 between a waste incineration plant and a farm outside Zürich, Switzerland. It extracts about 900 tons of carbon dioxide from the air near the waste plant, and pumps it into a greenhouse where the gas feeds assorted vegetables. Jan Wurzbacher, director and co-founder of Climeworks, the firm that manufactured the plant, told Fast Company that it is “commercially attractive”. But even Bloomberg’s report on the plant didn’t bother to mention the machine’s price.
According to New Scientist, the makers claim that the current cost for large-scale CO2 sequestration is $600 per ton, and they expect to equal this figure. If this is true, the plant, including the electricity to turn its fans and heat it up to boiling point periodically, will cost $540,000 to operate for a year.
In another article on the Climeworks plant, the makers claim to already have broken the $600 per ton barrier. That piece also claims that 10 gigatons of CO2 need to be removed from the atmosphere every year to halt the pace of global warming. Whether or not that is true, necessary or even desirable, the catastrophist publication Carbon Brief agrees. This means we’d need 11-million of these plants operating concurrently. Accepting the $600 per ton cost at face value, that works out to a price of $6-trillion per year. That sounds “commercially attractive” only if you’re a shareholder of Climeworks.
Then there’s the CityTree. If you like your cityscapes futuristic, it doesn’t look half bad. Its 3.5m2 vertical square panel, covered in moss and supported by two benches, is claimed to be more effective at filtering atmospheric pollution than trees. It does the work of 275 trees, according to the marketing material of the manufacturer, removing about 90kg of particulates and some 240 tons of carbon dioxide from the air per year. Where all that stuff would fit in such a small contraption is anyone’s guess. I already smell a rat.
The price for one of these urban accoutrements? According to futurism.com, it is “fairly cost-effective” at $25,000 per unit. It would be astonishing that such a small, simple design has 27% of the capacity of the far more substantial Swiss carbon capture plant. If we take the manufacturer’s claims at face value, its upfront costs work out to $20 per ton of sequestrated CO2 over five years, although that excludes any running costs. This extraordinarily low figure is another reason we shouldn’t believe any of these claims.
What alternative do we have to expensive carbon capture contraptions? (Again, supposing that reducing atmospheric CO2 levels is necessary to avoid catastrophic climate change.)
Trees, of course. Increasing CO2 levels in the atmosphere have already resulted in a greening world, as one might expect. After all, plants love CO2, which is exactly why the Swiss capture plant is connected to a greenhouse.
Calculating how much carbon is sequestered per year per tree (or per unit of afforested area), is a complex task. It requires data on tree species, density, age and much more. Generally, trees are best at sequestering carbon when they are large and still growing fast.
If we work backwards from the claims by CityTree, 275 trees sequestering 240 tons of CO2 per year gives a figure of 0.9 tons per tree per year. However, a calculation involving silver maple in the US, using the per-tree calculator linked above, works out to 0.2 tons per tree per year. The Climeworks founder told Future Company that a tree takes 50kg out of the air per year, which would make their plant do the work of 18,000 trees. Yet another source says 98 mature trees sequester 1 ton of CO2 per year, which makes it about 10kg per tree per year. Yet again, we can’t seem to rely on any of the claims made by marketers. This paper gives a figure of 0.28kg per square metre, which points to an even lower value than 10kg per tree.
Let’s suppose 10kg of carbon sequestration per tree per year is correct. This would mean that the CityTree can actually replace about 23,500 trees, not a mere 275. So either the 240 tons per year claim is a lie, or the 275 trees claim is gravely mistaken. I’m going to guess it’s the former. The Climeworks carbon capture plant, by the same assumptions, can replace 88,200 trees.
The cost of planting trees varies widely. The Plant a Billion Trees Campaign will do it for $1 a tree, but it can be done for as little as $0.20 per tree. That means the CityTree, at $25,000 not counting running costs, could be replaced by $4,700 worth of trees, if we’re generous enough to accept their 240 tons claim. If not, their own claim of replacing 275 trees puts the value of the $25,000 device at between $55 and $275.
At $0.20 per tree, the Climeworks carbon capture plant could be replaced by $17,640 worth of trees. Conversely, the cost per ton of CO2 sequestered by 20 cent trees works out to $19.60, which makes the Climeworks plant 30 times more expensive than an equivalent number of trees.
Meanwhile, in India, nobody is buying fancy-shmancy urban design or Swiss technology for scrubbing carbon. Instead, they get 1.5-million people together in the state of Madhya Pradesh and plant 67-million trees in 12 hours flat. That breaks a previous record of 50-million trees in 24 hours held by another Indian state, Uttar Pradesh.
Even assuming a 40% mortality rate among the saplings, the people of a developing country have achieved in less than two days what it would otherwise take 800 Climeworks plants to do. Depending on the numbers we believe, we’d need either 3,000 or 255,000 CityTrees to do the same.
Whether or not you believe that CO2 is a pollutant or that atmospheric CO2 levels are dangerously high, trees provide a great deal of environmental benefit. They offer habitat, improve the soil, scrub air of actual pollutants, and provide shade near buildings which reduces their energy costs. They’re nice to have around, especially in urban areas, and are good for the environment everywhere. They’re cheap, and they can be planted with no skill at all.
For showing up all the opportunistic green technology designers selling expensive devices and angling for vast new taxes to make them look worth the money, my hat’s off to India. Let’s follow their example. DM
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