[techmind (OP)]

Re: http://www.bbc.co.uk/news/science-environment-20556703 and similar

While it's probably true that not enough is being done to really curb CO2 emissions...

... the various green energy schemes (wind/solar farms etc) all require up-front cost and energy "investment" and have a significant energy-payback time. Is there any element of policy-makers being naive in expecting to see drops in CO2 output just yet?

Discuss...

(I do recognise that the green energy stuff at present-scale is still merely a drop in the ocean when considered worldwide)

[peppercorn]

Though not exactly answering your question, I wanted to bring up a report that's recently been in the news about how burning wood in the UK is not going to improve the CO2 levels any time soon; claiming in fact that replacing or co-firing wood in coal-power stations actually "dirtier" (to be read, 'more CO2 intensive') than the coal it is replacing!

Dirtier than coal?

I can see their thinking on this, in terms of chopping down mature trees (releasing years of stored CO2), but let's not throw the baby out with the bathwater! - If the wood can be supplied mainly from coppiced woods or similar, then there is no reason why burning the wood can not be near to carbon-neutral.  Obviously, the distance it's transported (the report raises a valid concern about importing wood via shipping/lorries) has an impact on it's overall 'greeness' but with planning and monitoring I think it can be kept to a minimum; ideally we'd grow all the wood as locally as possible but I imagine bringing it, say, central Europe (ideally using rail for the most part) is no worse than all the other crap things we import (and from much further away).

On the original topic, the concrete for building wind turbine towers, for example, has a CO2 impact, but as to how long it takes to wipe that out, I don't know.  Something like the long proposed Severn tidal scheme would appear far more of a concern in comparison.

[Mazurka]

I would suggest one of the biggest problems with such a discussion is that there has not been enough (robust) lifecycle analysis to compare the different technologies meaningfully.  This problem is compounded by received wisdom and "propoganda" deliberately and inadvertently spread by both sides of the debate. 

I recently came across this document
http://www.cse.org.uk/downloads/file/common_concerns_about_wind_power.pdf

Which appears to be quite well balenced - and if nothing else referrenced (although I do not have easy access to some of the journals referrenced, so I am taking the words of the authors on  trust to a certain extent)

I appreciate that wind is only one aspect of the debate, but it is currently the most viable and straightforward to deploy (both on and off grid) and is probably the most useful "low carbon" technology to discuss.

[evan_au]

A couple of quibbles about "common_concerns_about_wind_power.pdf"...

modern commercial turbines rotate more slowly (roughly 35 r.p.m.) producing a frequency of no more than 1.75 Hz, well below the threshold known to trigger photoepileptic seizures  [Which they ascribe to frequencies of 3-30Hz]

However, the article ignores the fact that most large turbines have 3 blades, resulting in a flash rate with a fundamental frequency around 5Hz, at the lower end of the frequency range of concern.

The intensity of the pressure wave emitted is measured in decibels (dB), which is usually recorded as a logarithmic scale to account for the enormous range of frequencies at which sound is audible to the human ear, i.e. 20–20,000 Hz

This is in a section talking about the enormous changes in sensitivity of human hearing at different frequencies, which is best represented in dB.

...but overall, an informative paper, primarily promoting wind power.

[yor_on]

I don't like the idea of using mature (old and slow growing) trees for it. They take a h* of a time growing back. which will end in a tree industry based on planting fast growing trees of worse quality, both energy wise, as well when used as building material. Those planks will warp, whereas slow growing wood will give good materials. That someone plant a tree for each one cut down doesn't tell the real story It's a industry, and the trees planted won't be the same as the ones cut down. We can see that here in Sweden, and I would expect it to be the same everywhere, where greed rule ones vision. Not implying that Sweden is any worse in that aspect than any other industrialized Country btw.

[CliffordK]

If we could use wood and crops for all of our energy needs, that would be great.  However, even 200 years ago, Europe was already running into wood shortages, thus sending out colonies around the globe and beginning to dig up the coal from the ground to supplement energy needs.  Had petroleum oil not been discovered, the whales could have been driven to extinction.

As far as planting trees, there is a growth curve (board feet or tons per acre?)  Someone must have calculated it.  Each tree species is different.  The big tree around here is the Douglas Fir.  They can get to a foot or a foot and a half or so in diameter in 50 years or so.  Certainly the rings become closer as the trees mature, but say putting on a 1/16", or perhaps 1/32" ring on a 4' diameter tree, 100' tall is a lot of new wood compared to a sapling. 

They do replant...  perhaps a half a dozen trees per tree that is harvested as not all survive, and they eventually will need thinning, but it takes more small trees than big trees to fill the land.  However, they plant almost exclusively Douglas Fir, and skip all the pines (sugar pine & ponderosa pine), cedars, hemlocks, spruces, and etc.  And the hardwoods are often even sprayed to kill them.  So mixed forests are cut, and mono-crops are replanted.

Now, Eastern Oregon is much drier than Western Oregon.  In some places there are huge stands of lodgepole pines, and whole forests are being wiped out by a pine beetle.  Every tree killed.

It is hard to imagine investing 50 to 100 years in a mono-crop of trees that could put the entire forest at risk of being destroyed by little bugs.

Anyway, one could certainly argue the benefits of using as much sustainable resources as possible which can include wood.

Many people, with a few acres, can provide 100% of their heating needs using wood.  And modern stoves are much more efficient than the old fireplaces.

[yor_on]

There are some tries for using bushes instead of trees, but it must also be a question about the CO2 produced. If a country has water then it can use that first, or if sun, then use that first. We should try to use the renewable, not CO2 producing energy sources first, after that look at alternatives. And another thing irritating me is to artificially raise the cost for some renewable a Country has, pointing to the situation world wide, that is greed to me. Like water, Sweden has a lot but the energy industry has laid cables exporting that energy, then raises the cost inside Sweden saying that we don't 'have enough' Used to be the state holding the reins, but no more.. Now it's plain profit for shareholders.. Some not Swedish at all. I like small self sufficient Countries that trade with each other for what the can't produce, but some industries should be owned by us all. That includes hospitals and energy, senior citizen arrangements too. That way the state get the profit and can use it for a country's needs. It's not that cable that offends me, it's the way we left thinking of us all, preferring greed. Sharing is a good thing, but only sharing profits with a very few?

It's a small planet. We can't afford that kind of free loaders any more.