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Earth

Entrepreneurs Fight Air Pollution With CO2-Reducing 'CityTrees' (cnn.com) 190

CNN is reporting on "CityTree", a unique 10-foot tall mobile installation which removes pollutants from the air." An anonymous reader quotes their report: Berlin-based Green City Solutions claims its invention has the environmental benefit of up to 275 actual trees. But the CityTree isn't, in fact, a tree at all -- it's a moss culture. "Moss cultures have a much larger leaf surface area than any other plant. That means we can capture more pollutants," said Zhengliang Wu, co-founder of Green City Solutions.

The huge surfaces of moss installed in each tree can remove dust, nitrogen dioxide and ozone gases from the air. The installation is autonomous and requires very little maintenance: solar panels provide electricity, while rainwater is collected into a reservoir and then pumped into the soil... "We also have pollution sensors inside the installation, which help monitor the local air quality and tell us how efficient the tree is." Wu said. Its creators say that each CityTree is able to absorb around 250 grams of particulate matter a day and contributes to the capture of greenhouse gases by removing 240 metric tons of CO2 a year... Wu also argued that the CityTree is just one piece of a larger puzzle. "Our ultimate goal is to incorporate technology from the CityTree into existing buildings," he said.

So far they've installed 20 CityTrees -- each of which costs about $25,000.
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Entrepreneurs Fight Air Pollution With CO2-Reducing 'CityTrees'

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  • by ShanghaiBill ( 739463 ) on Sunday June 11, 2017 @03:41PM (#54597707)

    CO2 is a global problem, not a city problem. There is no reason to locate CO2 consuming moss in any particular location, so it should be where it grows best, which is likely not downtown. This is obvious public "art" to make a statement, and not a serious attempt to mitigate AGW. Anyway, it does look cool.

    • by Entrope ( 68843 ) on Sunday June 11, 2017 @04:02PM (#54597803) Homepage

      Particulate emissions and NO2 levels are largely local problems, especially when you look at health effects versus distance from source. You should want to clean up air in cities because there are lots of harmful emissions there, and because a lot of people live there. Especially in developing nations, along with China and India, it's wildly expensive to adopt the kind of environmental controls that the US and Europe use. I'm not sure that this gadget provides $25,000 worth of benefit, but I agree with the overall idea.

    • Comment removed based on user account deletion
    • by jellomizer ( 103300 ) on Sunday June 11, 2017 @04:42PM (#54597973)

      I see this as part of the solution not a fix to the problem.
      Global warming is a big problem there isn't a magic bullet to fix the problem as there isn't one source that caused it.
      The building of cities has caused a lot of deforestation and this is one of the factors in the problem. So if we have condense ways of cleaning the air in cities we can still keep the advantage of the concrete cities while adding the benefit of plant life to help reduce carbon.

      Even if cities were plastered with these thing it isn't enough. But with combination of other changes such as moving to cleaner energy plants. More energy efficient transportation. We really slow down global climate change enough for the rest of the earth to heal from it, without having to make life changing sacrifices.

      • Comment removed based on user account deletion
    • Removing pollutants from the air is very much a city problem.
    • by guises ( 2423402 )
      This isn't about CO2. Capturing carbon requires mass, since that's where the carbon goes. Trees can capture carbon way more efficiently than moss can. Moss can capture particulate pollution pretty well though, and that tends to be a problem in cities.

      This does make sense in that respect, but with a few notable exceptions (Los Angeles) it's probably way more efficient to address the sources of the particulate pollution - usually coal power plants in/near the city.
      • Two of the worst cities for pollution in Europe are Paris and London - both due to a high density of cars. London got so desperate they set up a congestion charge zone, and Paris is establishing car-free areas to serve as havens from the smog.

        • by guises ( 2423402 )
          Okay. I mentioned Los Angeles because it's the same way, though it additionally has a problem (I'm told) with geography trapping the pollution in one place.
          • Yup.

            Though having grown up and spend most of my life (until recently) there, I can tell you that the air quality is far better now than it was back in the '80s.

    • Ivy league (Score:2, Interesting)

      by Anonymous Coward

      A simpler and cheaper way is to plant ivy. Ivy covered buildings were common 200 years ago.

    • These remove particulates and other air pollutants that are unique to cities.
    • by mattr ( 78516 )

      I don't know if that phrase is obviously true. CO2 and other pollutants have sources, which are localized somewhere (car exhaust, smokestacks, etc.). Some cities (Beijing, New York, Los Angeles) have localized weather conditions or inversions that cause pollutants to remain concentrate and remain localized, so if there is some way to remove the pollutants where they are concentrated and causing a huge number of people respiratory problems, I would be all for it.

      The only question I have is how well does this

    • CO2 is a global problem, not a city problem. There is no reason to locate CO2 consuming moss in any particular location, so it should be where it grows best, which is likely not downtown. This is obvious public "art" to make a statement, and not a serious attempt to mitigate AGW. Anyway, it does look cool.

      This is just some slick Grifters trying to suck up some U$25,000.00 from the City rubes to grow some moss. That shit grows all over the place out in the forests, only some stupid assed City-boys would fall for a con job like that!

  • Silly (Score:5, Insightful)

    by XXongo ( 3986865 ) on Sunday June 11, 2017 @03:42PM (#54597713) Homepage
    $25000, for moss?! How silly. They should have just planted trees.

    By the way, surface area is irrelevant if there isn't air flow past the surface, like there would be for an actual tree.

    • In a city $25,000 is fairly cheap compared to planting and maintaining 250 trees. Including the space they will take up in NYC you are paying over $1500 per square foot of space. 25k is a value

    • one of these is supposedly equal to 250 trees worth of carbon sink/air pollution scrub.
  • by Anonymous Coward

    This begs the question of whether CO2 is actually a pollutant or not.

    • Re: (Score:3, Informative)

      This begs the question of whether CO2 is actually a pollutant or not.

      No, it raises the question. Begging the question [wikipedia.org] means something completely different.

      CO2 is not a pollutant in the normal sense of causing a specific problem where it is concentrated, but in excess it does cause global problems regardless of what you call it.

      • Define 'excess'. 400 ppm? 750 ppm? 1000 ppm?
  • by Anonymous Coward

    How wonderful. Now that is something corporations can get behind.

  • by surfcow ( 169572 ) on Sunday June 11, 2017 @04:19PM (#54597855) Homepage

    So, each "citytree" removes 240 metric ton of CO2 a year?

    Right.

    That's 529,109 pounds of molecular CO2, per year.

    What does it do with it all?
    Turn it into biomass?

    Or unicorns?

    • by Zocalo ( 252965 )
      Those numbers are definitely really fishy and don't stand up to even basic scrutiny. Even if you allow for the device magically extracting the O2 and releasing it directly back into the atmosphere with 100% efficiency that still leaves almost 1 metric ton *per week* of carbon that has to go somewhere. Growth of the moss might take up some of it, but nothing like 1 metric ton/week, so where's the rest of it meant to be going?
    • I think that includes the mass of bullshit associated by this project. Sure it's expensive and useless, but it certainly resolves the issue of how to signal that you really, really, care about the environment, so much that you are willing to waste this much money on it. That at least gives you gravitas.

    • by hey! ( 33014 )

      Well, there are figures you can compare this to. A algae farm can produce (according to the literature) 36 tons of dry biomass per hectare per year, which probably represents an upper limit on biomass production per area. That's 3.6 kg/m^2/year. This thing is vertical, true, but the implication of the way you're reading it is that it produces over 20,000 kg/m^2/year.

      Clearly that's not possible, even with constant harvesting, but there's an even bigger problem: any CO2 removed as biomass will simply ret

    • by AmiMoJo ( 196126 )

      Check out this handy guide from the BBC: http://www.bbc.co.uk/schools/g... [bbc.co.uk]

      Like all green plants, CO2 and water are reacted to produce a kind of sugar and oxygen.

    • by sbaker ( 47485 ) on Monday June 12, 2017 @07:30AM (#54601273) Homepage

      Photosynthesis does: CO2 + Water => Sugar + O2...then the plant takes that sugar and turns it into biomass by converting it to starches and structural materials for the plant itself.

      Carbon has a molecular weight of 12 and Oxygen is 16...so CO2 is 25% carbon by weight. So to absorb 240 tons of CO2 per year - it's got to be generating (at a minimum) 60 tons of extra plant material per year - and more likely (because dead/living moss isn't all carbon) it's at least twice that.

      There is only just so much space in that concrete container - which means that a literal truckload of dead/living moss has to be removed from it every single week! Then, that biomass has to be disposed of in some way that doesn't simply re-release it into the atmosphere when it decays...you'd have to bury it or something.

      This is a ridiculous claim - it can't possibly be true. Even 24 tons a year wouldn't be credible - and 2.4 tons a year would seem high...the entire installation would haves to double in size every year to keep up even that more modest amount.

      What I'm sure happened here is that it's plausible that the moss has vastly more surface area than a tree - but moss is much more slow-growing than trees are - so the amount of CO2 it absorbs cannot possibly be as much per-unit-area as the leaves of a tree. So I'm betting that they did all of their math from surface area alone - and didn't stop to think beyond that.

      This is B.S.

  • If it captures 240 metric tons of CO2 a year, they better have it on a strong foundation. That is going to get really heavy.
  • Just not for $25,000

    Here's the thing... We need to remove CO2 from the atmosphere, the only viable way to do this is photosynthesis, then, we need some way to sequester the bulk material. If the numbers they quote are accurate, 275 trees, then this could be interesting. Also, I honestly don't see how something like this isn't less than about $500 worth of stuff.

    The moss "filters" should be replaceable. Grow them, when they are done, remove them, dry and press them in to flat surface then laminate, violla! a

    • We need to remove CO2 from the atmosphere, the only viable way to do this is photosynthesis,

      A much better way to remove next year's CO2 from the atmosphere is to leave the carbon in the ground. Close a coal plant, and replace it with PV panels. After we've done that, we can focus on last year's CO2.

  • by Hentes ( 2461350 ) on Sunday June 11, 2017 @04:32PM (#54597921)

    There used to be a lot of confusion about how the carbon cycle [wikipedia.org] works but I hoped that we're over that now. In short, plants use up only as much carbon as they need to grow, the rest just goes through them. This installation will never become carbon negative.

    It might help with air pollution, but for $25000 apiece planting 275 trees may still be more economical.

    • It's not really for carbon, that's just hype. It's for particulate pollution. It tends to be a serious problem in urban areas due to a very high density of combustion-powered vehicles.

      I'd like to see someone calculate how much of this moss you'd need to improve air quality though - I suspect it will be an impractical amount.

    • by AmiMoJo ( 196126 )

      If trees would be better really depends on a lot of factors. Trees take up more room and can have a negative effect on things around them (shade, roots). Having 275 of them means a lot of maintenance in a lot of different places. Trimming, safety evaluations, care when they get diseases etc.

      But on the other hand, in the right place trees can be great. The more options we have the better.

  • This structure delivers the equivalent of a large park with hundreds of trees worth of pollution control to a street corner. Think about that for a little while. A city with one or more of these in every major plaza is equivalent to building a functioning city inside of a forest with direct benefits to human health. There are few public investments more worthwhile than this for major cities.
    • by XXongo ( 3986865 )

      This structure delivers the equivalent of a large park with hundreds of trees worth of pollution control to a street corner.

      Except it's not, and it doesn't. You are ignoring that weasel phrase "up to".

      People in the thread above have already shot holes in that claim that it can remove 240 metric tons of carbon dioxide a year-- a ton every day and a half? Where does that carbon go? Who hauls it away?

  • Is that what we're moving towards? Tree Farms and Hybrid Forests to counter our ecological damage? Or are we going to go for a Centauri Preserve?

  • It's equivalent to blab blah blah trees, I just need a $XX million dollar grant to make it happen.

    So what you are saying is it is a shit idea and no one is stupid enough, except for gov't, to pay for it.

  • This is a perfect example of green-washing. Let's start with their own claimed numbers. "250 grams of particulate matter a day". Let's give them perfect efficiency and say that is 100% carbon. 250 grams x 365 days = 91,250 grams. Divide that by 1000 to and we see that this art installation claims 91.25 kilograms of particulate per year. This is indeed more than the average mature tree that captures 21.7 kilograms of carbon per year.

    Now let's compare that to their claim of "greenhouse gases by removing 240 m

  • They claim to capture 240 tons of CO2, which turns into 60 tons of organic carbon retained by moss growth. And then, where will it go? They cannot let the moss culture grow without limit in their "tree".

  • by alzoron ( 210577 ) on Sunday June 11, 2017 @07:58PM (#54598749) Journal

    Where is all that carbon the moss is sequestering going? 240 metric tons of carbon doesn't just poof into nothingness. 240 metric tons a year is just under a ton a day. Based on the size of these things they should weigh somewhere between 4-8 metric tons. With the figures given they would be doubling in weight every 1-2 weeks from just the carbon. That doesn't sound very autonomous or low maintenance.

  • Is this moss robust? Does it require much maintenance, or does it take care of itself fairly well, given the basics it needs? Could you cultivate it in large grid-like structures, which you also ventilate, for maximum air-renovating effects? Given a properly designed structure/framework and the basics it needs to live and grow, would it propagate itself across the structure/framework you provide for it? What I'm getting at is, building 'air recycling plants' (pun unintentional) in locations around the world

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