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Solar arrays better than trees for climate, study finds
🕑 Added 2024-01-08 16:00:08 +0000 UTC[This is a transcript with links to references.]
What is better, planting trees or covering the same area of land with solar panels? A group of geoscientists from Israel just looked at this, and they say that solar panels come out way ahead.
Trees breathe carbon dioxide, which makes planting trees a fairly obvious and technologically simple way to mitigate global warming. Trees and other vegetation take up about 2 billion tonnes of carbon dioxide annually, and they use it to grow. They create what’s known as “biomass”, that’s basically living stuff that stores carbon. Yes, you are, too.
Most of that carbon is released when the trees, or we, die and rot away, but trees deposit part of the carbon into the soil where it can remain for a long time. Indeed, those dreaded fossil fuels are basically plants that have been dead and underground for a very very long time.
A fairly obvious way of decreasing carbon dioxide levels in the atmosphere is therefore to plant more trees. Problem is that planting trees competes with other land uses, such as planting crops that people would like to eat, or planting cows that they’d much rather eat. And in most fertile areas that people aren’t currently using for food production, there are either trees already or humans are busy chopping them down.
This is why geoscientists say the best places to plant trees and other vegetation are semi-arid areas where there’s some rainfall but not much. Basically, these are areas that aren’t good enough for agriculture, but still many plants can grow there if one just plants them, and those could take up a lot of carbon dioxide.
These areas that have potential for reforestation are huge parts of southern Africa and southern America, as well as Russia, and eastern Australia, but also in some parts of Europe. According to estimates, the potential area is almost 1 billion hectares, or about the size of the entire United States.
But here’s the issue, those areas that are prime candidates for reforestation are also good to put up solar panels, which raises the question just which is better for the climate.
So this group of research went and crunched the numbers. They compared a “forest” of solar panels and its potential for reducing global warming with an actual forest of trees.
The question of which is better isn’t just about how much carbon dioxide they remove or avoid, the question is also how much sunlight they absorb or reflect, quantified in the “albedo”.Both trees and solar panels absorb quite a lot of light compared to the dry ground, but just how much depends on the type of trees. The other main factor included in the study is “break-even time,” that’s how long it takes until a forest or solar installation fully offsets the warming created by its plantation or installation.
Their analysis shows that installing solar cells took about 2 point 5 years to pay off the climate change created by their manufacturing, installation processes, and changes in surface reflection. Planting a forest, however, would take over 100 years of photosynthesis to offset the warming caused by its planting and reflectivity.
They also found that installing fields of solar panels would be roughly 100 times more effective at mitigating carbon emissions than planting a forest. Even in less-arid climates, a forest of solar panels was over 20 times more effective at offsetting its own climate costs than a forest.
So, solar panels are better than trees, science said it.
Well, not quite. Indeed, the authors seem to be somewhat concerned that someone might take their results out of context. I wonder why? So they stress that they didn’t look at forests in general, just at the reforestation potential in those semi-dry areas. So not like we should chop down the rain forest and put-up solar panels there.
The other issue is that they didn’t look at the economic question. Because, you know, generating energy with solar panels isn’t of much use if there’s no power lines going there. Trees have the advantage that you don’t need to plug them in.
Comments
Yes we need both, because wood can be burned as an energy source (including power generation) and it has the advantage of providing long-term storage and short-term "dispatchability". Another way of saying this is to point out that a forest and a solar farm can both provide solar-derived energy, but only one of them takes CO2 out of the atmosphere and stores it. The comparison I would make is using the parameter "kW/ha". By this measure, direct solar and wind power are far ahead of biofuels, which accords with the study being reported here. (If you count rooftop solar and can say that its land-use is zero - assuming no other economic use for the rooftop - then rooftop solar is infinitely good by this measure.) Therefore it is predictable that wind power and direct solar will continue to dominate the growth of renewables for decades to come. But they are not as good as biofuels for providing storage and dispatchability (and liquid biofuels have special value for transport). So if you have a market which fairly values those attributes, biofuels will have their role. I would guess the renewable transition will look something like this: - 30% wind power - 30% direct solar power, heating and drying - 30% biofuels (all forms) - 10% the expensive rest (hydro, geothermal and nuclear among others) But nobody cares about one individual's guess, nor should they. What is really needed is correct pricing of CO2 emissions by the TAO or tradeable absorption obligation applied globally at zero-net or whatever value is needed for avoiding dangerous anthropogenic interference with the climate system. That, and good market signals for storage and dispatchability versus intermittent sources and controllable demand, will enable a renewable transition which will provide the answers about market share that one can only guess at. I'm curious about the importance of a forest offsetting the "warming caused by its planting and reflectivity". I'm not sure what the former is and the latter is accentuated by the study's focus on semi-arid areas. I would be interested in a study that looked at the full scope for biofuels as part of the energy mix using something like 20-25% of the Earth's total populated land area. 1 billion hectares, about the area of the USA is only 7% of that total.
I just repeat what others say: We need both!
