Carbon emissions Whack-a-Mole

Article in R&D

Where does carbon fit into greenhouse gas control strategies?
 

May 29, 2009

Cutting down forests for agriculture vents excess carbon dioxide into the air just as industrial activities and the burning of fossil fuels do. But whether policies to stabilize greenhouse gases in the atmosphere should include this terrestrial source of carbon dioxide is under debate. According to a new study this week in Science, failing to include land use changes in such policies could lead to massive deforestation and higher costs for limiting carbon emissions.

Original:

Science 29 May 2009:
Vol. 324. no. 5931, pp. 1183 - 1186
DOI: 10.1126/science.116847

Reports

Implications of Limiting CO₂ Concentrations for Land Use and Energy

Marshall Wise,Katherine Calvin,Allison Thomson,Leon Clarke,Benjamin Bond-Lamberty,

Steven J. Smith,Anthony Janetos,James Edmonds

Limiting atmospheric carbon dioxide (CO₂) concentrations to low levels requires strategies to manage anthropogenic carbon emissions from terrestrial systems as well as fossil fuel and industrial sources. We explore the implications of fully integrating terrestrial systems and the energy system into a comprehensive mitigation regime that limits atmospheric CO₂ concentrations. We find that this comprehensive approach lowers the cost of meeting environmental goals but also carries with it profound implications for agriculture: Unmanaged ecosystems and forests expand, and food crop and livestock prices rise. Finally, we find that future improvement in food crop productivity directly affects land-use change emissions, making the technology for growing crops potentially important for limiting atmospheric CO₂ concentrations.

Quote:

Originally Posted by dawei 

I don't really get it. I mean I can understand how deforestation might increase with carbon laws due to rising demand for biofuels, but what do they propose should be done about it? Deforestation has been uncontrollable for decades. There are 100 reasons to not chop down a forest, and if none of these have been strong enough to actually have well enforced deforestation laws then I don't see why carbon would be any better.

 

Maybe they could put laws in place to reduce deforestation in the US or Europe, but in places like Brazil or Africa it just doesn't seem like it'll happen.

Personally, what the article shows is that there is no way to reduce carbon emissions without a large net reduction in the amount of energy that gets used.  You can't just move to different energy sources, using the same total number of joules per second.  Society will have to limit energy use, not just the type of energy used. 

Limiting energy use is a much much harder proposition, so hard that I argue it is impossible.  There is no way you can get the boutique greens, who as George Carlin acidly and correctly put it want a nice safe habitat to drive around in their Saabs and Volvos, to reduce their net energy use.  They still want their large flat panel tvs, their front-loading washer/dryers, personal automobiles, etc.  But in addition to having all the toys they want to feel like they are "making a difference" because they have either made minor gains in energy efficiency or now some small fraction of the energy they are using comes from a different source that isn't directly tied to fossil fuels.  What the article shows is that without reducing the toys, it is likely carbon emissions will continue to rise. 

Cynically put, everyone wants to regulate carbon until they realize that true change will affect them as well.  This is why we will see a shift in emphasis from emissions reductions to adaptation in terms of climate change.  No politician has the backbone to tell people the truth about what needs to be done, or what lifestyles in the developed countries would look like if we were really serious about reducing carbon emissions. 

Quote:

Originally Posted by dana1981 

I certainly agree that in practicality we need significant energy consumption reductions.

 

But in theory, why couldn't we build a bunch of concentrated solar thermal plants in deserts, put up a bunch of wind turbines and photovoltaics and geothermal plants, and switch our transportation to electric cars?  Seems to me like in theory, that would seriously reduce carbon emissions without directly impacting things like deforestation.

Suppose, just for grins, we assume that all electricity used by people in the US will be generated using PV material.  Best PVs are about 30% efficient and the US uses about 1.3 kW per capita per hour.  That means, if you grind through the math assuming a solar flux of around 350 W/m^2, you need a total solar collector area of around 400 km by 400 km assuming the sun shines brightly every day and there are no clouds or dirt on the collectors (in reality, you would probably need to double or triple the size of the array to have enough excess capacity in the system to be practical).  Building something of this scale, even distributed, is going to lead to unintended enviromental consequences, aside from the environmental damage it will entail. (Wind turbines have similar issues, and large scale wind-farm deployment implies you can basically kiss migrating fowl goodbye.)

Furthermore, there is a very real issue of how you deal with supplying electricity at night, when the sun is behind the limb of the planet.  You could propose you are going to build massive energy storage batteries, but my guess is you run into issues that there isn't enough room to put these, and you lose energy storing the batteries, and produce carbon manufacturing them, so that in the end it is likely you haven't really reduced carbon emissions as much as you might think. 

I just don't get how these systems are supposed to work in practice, it seems like people who propose them haven't thought seriously and realistically about the magnitudes of the problems associated with getting carbon out of the energy supply.  All these alternative energy sources at some level come down to "and then a miracle occurs" to make them work in reality. 

Quote:

Originally Posted by captaint 

Perhaps this is pie-in-the-sky, but shouldn't we focus on supplying our own energy needs at the local level, perhaps house to house?  It seems that incentivising several million people to provide their own power through solar, geothermal, etc might be a better approach.  This could also be the incentive people need to reduce their energy usage (supposing the cost for an energy comany providing it would be extremely high).  Granted you still have the issue of production of all those systems.   

Perhaps I am thinking too personally about this, as I would much prefer to be my own provider.

Each four-person residence would have to have the equivalent of 60' by 60' of solar collectors, or 3600 ft^2.  The average home size in the US is 2300 ft^2.  So you would need 50% more area for solar collectors than floor space in the house.  Of course, people living in apartment buildings, condominiums etc. will be even more space challenged in terms of where to put the solar panels.  This calculation also works only for the equator, as you go up in latitude the area required becomes even larger. 

There are similar issues with wind generators, that a generator large enough to power a house for 4 is too large and too noisy to put near a house (and in your typical suburban housing development, net efficiency would go down with wind generators spaced at every house), and very few people live near enough to geothermal vents to make that a credible option. 

The bottom line is we all use too much energy for their to be any realistic solution.  Perhaps if the energy use for a family of four were on order of a few hundred watts-hrs instead of 5000, then you could talk sensible individual options.  But I don't see people voluntarily giving up all their toys and gadgets to get energy consumption to decrease by a factor of 10. 

Quote:

Originally Posted by dana1981 

I was thinking mainly of renewable sources like concentrated solar thermal and geothermal, gcnp.  Solar thermal can provide energy overnight by storing it in a medium like salt or water.  Geothermal can provide power anytime.

 

Cap'n - supplying out own energy on a local level is a good solution, but from a cost standpoint, it's more expensive than building large power plants.  A solar thermal plant can provide power at 15 cents per kWh, but solar panels are almost twice that.

Power is power, and whether you store energy generated by PVs or as hot salt the efficiency is the same, about 30%, so the total amount of collector area is on order of 600 km by 600 km.  So storing hot salt will still require huge storage reservoirs, and concomittant environmental damage constructing them and when one of them ruptures (and you know it will).  This is one of the inescapable facts of the problem.  No matter how you end up with a joule of energy in terms of electricty, you have to start with a certain number of larger joules of photons from sunlight.  It is like the old sci-fi story "Cold Hard Equations" about the girl who stows away on a spaceship and has to be thrown out the airlock because there isn't enough fuel. 

As for geothermal, I doubt there is anywhere near enough on a national level for it to be anything other than a boutique option at a local level. 

Anyway, I'm not saying that this shouldn't be done, I'm saying it is a vast undertaking and ignoring these large and unresolved issues from the start is asking for problems in getting it completed.