6 ms·

Can you prove that or back that up with some facts?

by jweir 7y ago

spydum 7y ago
I suspect this is because you generate power all year round, while a shade tree doesn’t help heat your house in winter..
village-idiot 7y ago
That’s pretty trivial to prove. Grid tied systems sell excess electricity back at bulk rates, at least in some states, which means that the solar panels are producing more electricity than the home needs for cooling. Thus such a house is actually spending negative carbon on cooling, since they’re providing green energy for their neighbors. A shade tree can reduce your need for electricity, but it can’t turn you into a net producer.
- jweir 7y ago
  Depending on the tree(s), it could be consuming CO2 24 hours a day, year round, solar is just part of the day and only reaches capacity for a brief moment. I don't know the numbers to show the difference. That is why I asked for some facts which the OP seems to know.
  - TallGuyShort 7y ago
    Trees consume CO2 because it's part of photosynthesis, so that's actually on the same schedule as a solar panel's electricity production. At night they're actually continuing to release some of that CO2.
  - village-idiot 7y ago
    A single average fully grown tree can sequester about 88lbs of CO2 per year according to the Center for Urban Forest Research, which is part of the US Forest Service. The average electricity service in the US produces about 1lb of CO2 per kWh, meaning that your solar panel needs to reduce your consumption by only 88 kWh per year below what your shaded house cost would be to be a net positive over a shade tree.
    - VBprogrammer 7y ago
      Don't quote me on this but from memory a tree is able to sequester a lot more in the first couple of years than as a fully grown tree. Intuitively that makes sense.
      - village-idiot 7y ago
        Yes, that is true. The carbon sequestration is greatest when the tree is turning CO2 into more tree (e.g. when it’s growing). This process largely stops as a tree hits maturity, and the CO2 is mostly returned when the tree burns or rots. I’m making the explicit assumption that a shade tree will probably be fully grown.
  - CydeWeys 7y ago
    Trees don't really continuously "consume" CO2 in this manner. The only CO2 removed by a tree is the carbon that ends up permanently Incorporated in the wood itself. And if you burn that wood, it's all released back into the air. Even if it just dies and decays, some of it ends up being released.
    - zitterbewegung 7y ago
      Yea, so to sequester the carbon either build something out of it or dump it into the ocean. Maybe build a boat?
      - CydeWeys 7y ago
        Rather than sequestering all this carbon into wood and then trying to figure out what to do with the wood so that it doesn't decompose over time and release the CO2 back into the air, it'd make more sense to stop digging up lots of carbon from underground (where it's been stable for hundreds of millions of years in the form of coal and oil) and burning it to release the CO2 into the air. We already have amazing reserves of CO2, and we're digging them up and releasing them by burning them! Trees are just a tiny band-aid on top of this massive harm we're self-inflicting.
        zitterbewegung 7y ago
        Why can’t we do both ?
        CydeWeys 7y ago
        We can and should, but there's more impact to be had from ceasing to dig up the buried carbon and burning it. That's the equivalent of not punching holes in the hull, whereas planting trees is like bailing out the boat -- you'd rather it just didn't leak!
ChuckMcM 7y ago
I can tell you how I reason to it. According to many sources, but I will cite this one[1] a single tree converts about 50 lbs of CO2 in a year. There are three trees on my property, a city tree (planted by the city) and two Birch trees planed by the original developer. All are deciduous so lose leaves in the winter but we'll give them full credit anyway, so call it 150 lbs of CO2 a year. My rooftop solar system nominally puts out 5.2 kW of power under full sunlight, although efficiencies cut that down to around 4.8 kW net into the grid. I have over 10 years of data from the system, drilled down though it averages out to about 4.5 "solar hours" per day with an average daily output of about 22 kWH per day or about 8 MWH per year. The US Energy Information Association (EIA) tracks a number of statistics, but the one that is most relevant is the number of metric tons of CO2 per MWH per state. You can see California's number in this report : https://www.eia.gov/electricity/state/california/ https://www.eia.gov/electricity/state/california/ is 474 lbs per MWH. Using that number, my rooftop solar system "saves" (which is to say doesn't generate) about 3,792 lbs of CO2 a year. Which, is way more than the 150 lbs a year the trees are taking out of the air. This is why the 1.2T trees, or 160 per person, is such a large number. A family of four would need to plan 640 trees on their lot, which would remove 32,000 lbs of CO2, which is a lot. To match my solar panels I would need to plant an additional 76 trees. What you can take away from that is that solar panels in places where you can't put trees are a solid alternative. And planting trees rather than letting unused land sit idle as a field of grass is also a good plan. As a home owner, solar, even in places where it won't generate all your energy needs, will help cut CO2 emissions. [1] https://projects.ncsu.edu/project/treesofstrength/treefact.htm https://projects.ncsu.edu/project/treesofstrength/treefact.h...
- yathern 7y ago
  Good reasoning! I agree with the basic premise - but I don't think you can ignore the CO2 cost to make a solar panel, vs to use one. A tree reduces CO2 as it's being 'built'. A solar panel requires many materials that are refined through various industrial processes - likely some of which produce CO2 - not withstanding the transportation CO2 cost. That all being said, I don't mean to disparage anyone who uses solar panels - and if you already have them (sunk cost) - less trees seems about right, to reduce carbon footprint.
Robotbeat 7y ago
It can be shown both bottom-up and top-down, but I prefer the bottom-up: Photosynthesis is usually an order of magnitude more efficient than photovoltaics: https://en.wikipedia.org/wiki/Photosynthetic_efficiency https://en.wikipedia.org/wiki/Photosynthetic_efficiency ...an individual leaf might be peak out at 3% efficient, but it is operating just a portion of the year (maybe about a third to a half at full performance) and also much light gets reflected, absorbed by branches, or misses the leaves entirely. Additionally, photovoltaics peak at 40% efficiency but get about 15-20% efficiency typically and can function the entire year (unless fully covered by snow). And they're displacing electricity produced primarily from fossil fuels which are burned at 30-40% efficiency. Now from a top-down perspective: forests (in this case calculated by replacing cropland with forests) are estimated to sequester about 2 to 10 tons of CO2 per acre per year. https://fas.org/sgp/crs/misc/R40562.pdf https://fas.org/sgp/crs/misc/R40562.pdf In principle, an acre of about 40% solar photovoltaic system with a 25% capacity factor could produce about 3.5GWh per year. But typically, about exactly one tenth that is done in practice: 0.35GWh/year/acre. Since you'd be displacing electricity from the US grid, which is currently about 420 grams of CO2 per kWh (based on my calculations of the most recent eia.gov figures, but you can find similar figures by Googling), that's equivalent to 147 metric tons of CO2 per acre per year for typical photovoltaics (and over 1000 metric tons per acre per year in the idealized case). This person's calculations reach similar conclusions: https://www.solarpowerrocks.com/environment/installing-solar-like-creating-small-mature-forest/ https://www.solarpowerrocks.com/environment/installing-solar... So absolutely, it's better to use solar panels than trees, at least until the grid is fully or nearly-fully saturated by solar. ...BUT once we fully clean the grid, trees have some advantages: 1) they efficiently suck CO2 out of the air and store it, not just produce the energy. That means you can actually draw-down CO2, producing negative emissions. 2) They're scalable. A tree is like a solar farm, CO2 direct air absorption system, and a chemical factory but can be planted as just a seed. It may not be "efficient", but being self-replicating and scalable is pretty powerful.
- ncmncm 7y ago
  Your first paragraph contradicts the rest, I assume by accident.

Can you prove that or back that up with some facts?

by jweir 7y ago

Can you prove that or back that up with some facts?

I suspect this is because you generate power all year round, while a shade tree doesn’t help heat your house in winter..

village-idiot 7y ago

That’s pretty trivial to prove. Grid tied systems sell excess electricity back at bulk rates, at least in some states, which means that the solar panels are producing more electricity than the home needs for cooling. Thus such a house is actually spending negative carbon on cooling, since they’re providing green energy for their neighbors. A shade tree can reduce your need for electricity, but it can’t turn you into a net producer.

jweir 7y ago
Depending on the tree(s), it could be consuming CO2 24 hours a day, year round, solar is just part of the day and only reaches capacity for a brief moment. I don't know the numbers to show the difference. That is why I asked for some facts which the OP seems to know.
- TallGuyShort 7y ago
  Trees consume CO2 because it's part of photosynthesis, so that's actually on the same schedule as a solar panel's electricity production. At night they're actually continuing to release some of that CO2.
- village-idiot 7y ago
  A single average fully grown tree can sequester about 88lbs of CO2 per year according to the Center for Urban Forest Research, which is part of the US Forest Service. The average electricity service in the US produces about 1lb of CO2 per kWh, meaning that your solar panel needs to reduce your consumption by only 88 kWh per year below what your shaded house cost would be to be a net positive over a shade tree.
  - VBprogrammer 7y ago
    Don't quote me on this but from memory a tree is able to sequester a lot more in the first couple of years than as a fully grown tree. Intuitively that makes sense.
    - village-idiot 7y ago
      Yes, that is true. The carbon sequestration is greatest when the tree is turning CO2 into more tree (e.g. when it’s growing). This process largely stops as a tree hits maturity, and the CO2 is mostly returned when the tree burns or rots. I’m making the explicit assumption that a shade tree will probably be fully grown.
- CydeWeys 7y ago
  Trees don't really continuously "consume" CO2 in this manner. The only CO2 removed by a tree is the carbon that ends up permanently Incorporated in the wood itself. And if you burn that wood, it's all released back into the air. Even if it just dies and decays, some of it ends up being released.
  - zitterbewegung 7y ago
    Yea, so to sequester the carbon either build something out of it or dump it into the ocean. Maybe build a boat?
    - CydeWeys 7y ago
      Rather than sequestering all this carbon into wood and then trying to figure out what to do with the wood so that it doesn't decompose over time and release the CO2 back into the air, it'd make more sense to stop digging up lots of carbon from underground (where it's been stable for hundreds of millions of years in the form of coal and oil) and burning it to release the CO2 into the air. We already have amazing reserves of CO2, and we're digging them up and releasing them by burning them! Trees are just a tiny band-aid on top of this massive harm we're self-inflicting.
      - zitterbewegung 7y ago
        Why can’t we do both ?
        CydeWeys 7y ago
        We can and should, but there's more impact to be had from ceasing to dig up the buried carbon and burning it. That's the equivalent of not punching holes in the hull, whereas planting trees is like bailing out the boat -- you'd rather it just didn't leak!

ChuckMcM 7y ago

I can tell you how I reason to it. According to many sources, but I will cite this one[1] a single tree converts about 50 lbs of CO2 in a year. There are three trees on my property, a city tree (planted by the city) and two Birch trees planed by the original developer. All are deciduous so lose leaves in the winter but we'll give them full credit anyway, so call it 150 lbs of CO2 a year. My rooftop solar system nominally puts out 5.2 kW of power under full sunlight, although efficiencies cut that down to around 4.8 kW net into the grid. I have over 10 years of data from the system, drilled down though it averages out to about 4.5 "solar hours" per day with an average daily output of about 22 kWH per day or about 8 MWH per year. The US Energy Information Association (EIA) tracks a number of statistics, but the one that is most relevant is the number of metric tons of CO2 per MWH per state. You can see California's number in this report : https://www.eia.gov/electricity/state/california/ https://www.eia.gov/electricity/state/california/ is 474 lbs per MWH. Using that number, my rooftop solar system "saves" (which is to say doesn't generate) about 3,792 lbs of CO2 a year. Which, is way more than the 150 lbs a year the trees are taking out of the air. This is why the 1.2T trees, or 160 per person, is such a large number. A family of four would need to plan 640 trees on their lot, which would remove 32,000 lbs of CO2, which is a lot. To match my solar panels I would need to plant an additional 76 trees. What you can take away from that is that solar panels in places where you can't put trees are a solid alternative. And planting trees rather than letting unused land sit idle as a field of grass is also a good plan. As a home owner, solar, even in places where it won't generate all your energy needs, will help cut CO2 emissions. [1] https://projects.ncsu.edu/project/treesofstrength/treefact.htm https://projects.ncsu.edu/project/treesofstrength/treefact.h...

yathern 7y ago
Good reasoning! I agree with the basic premise - but I don't think you can ignore the CO2 cost to make a solar panel, vs to use one. A tree reduces CO2 as it's being 'built'. A solar panel requires many materials that are refined through various industrial processes - likely some of which produce CO2 - not withstanding the transportation CO2 cost. That all being said, I don't mean to disparage anyone who uses solar panels - and if you already have them (sunk cost) - less trees seems about right, to reduce carbon footprint.

Robotbeat 7y ago

It can be shown both bottom-up and top-down, but I prefer the bottom-up: Photosynthesis is usually an order of magnitude more efficient than photovoltaics: https://en.wikipedia.org/wiki/Photosynthetic_efficiency https://en.wikipedia.org/wiki/Photosynthetic_efficiency ...an individual leaf might be peak out at 3% efficient, but it is operating just a portion of the year (maybe about a third to a half at full performance) and also much light gets reflected, absorbed by branches, or misses the leaves entirely. Additionally, photovoltaics peak at 40% efficiency but get about 15-20% efficiency typically and can function the entire year (unless fully covered by snow). And they're displacing electricity produced primarily from fossil fuels which are burned at 30-40% efficiency. Now from a top-down perspective: forests (in this case calculated by replacing cropland with forests) are estimated to sequester about 2 to 10 tons of CO2 per acre per year. https://fas.org/sgp/crs/misc/R40562.pdf https://fas.org/sgp/crs/misc/R40562.pdf In principle, an acre of about 40% solar photovoltaic system with a 25% capacity factor could produce about 3.5GWh per year. But typically, about exactly one tenth that is done in practice: 0.35GWh/year/acre. Since you'd be displacing electricity from the US grid, which is currently about 420 grams of CO2 per kWh (based on my calculations of the most recent eia.gov figures, but you can find similar figures by Googling), that's equivalent to 147 metric tons of CO2 per acre per year for typical photovoltaics (and over 1000 metric tons per acre per year in the idealized case). This person's calculations reach similar conclusions: https://www.solarpowerrocks.com/environment/installing-solar-like-creating-small-mature-forest/ https://www.solarpowerrocks.com/environment/installing-solar... So absolutely, it's better to use solar panels than trees, at least until the grid is fully or nearly-fully saturated by solar. ...BUT once we fully clean the grid, trees have some advantages: 1) they efficiently suck CO2 out of the air and store it, not just produce the energy. That means you can actually draw-down CO2, producing negative emissions. 2) They're scalable. A tree is like a solar farm, CO2 direct air absorption system, and a chemical factory but can be planted as just a seed. It may not be "efficient", but being self-replicating and scalable is pretty powerful.

ncmncm 7y ago
Your first paragraph contradicts the rest, I assume by accident.