Those of us of a green persuasion are always banging on about carbon emissions
aren't we? It must drive the fossil fuel fans up the wall having to listen to people like me
constantly droning on about how renewable energy might actually stop us destroying civilization
as we know it and killing off hundreds of thousands of species of plants and animals.
I mean to listen to us lot anyone would think we cared more about those things
than we did about the relentless march of human progress and the all-important annual increase
in global GDP! And let's face it, nothing's more important than an increase in GDP is it?
But there's always been a bit of a question, mark at least in the minds of some people,
about one of the key claims of green energy. And it's all to do with how the carbon emission
numbers really stack up when you step away from the end product comparisons like fossil fuel power
plant carbon emissions versus wind turbine carbon emissions and start focusing on all the other
stuff involved in producing transporting maintaining and ultimately disposing of
these products. Some argue that when you do that the playing field levels up significantly.
So are they right? Does a full life cycle analysis of renewable energy
sources versus fossil fuel energy sources reveal any nasty surprises?
Well let's have a rummage around and see what we can find out.
Hello and welcome to just have a think. Back in 2013 a well-known climate sceptic organization
called the Global Warming Policy Foundation started touting around a study published that year
that said that nuclear and fossil fired power stations have much better energy returns on
investment or EROIs than renewable sources. They got quite widely panned at the time
and the paper itself was rebutted by a peer review analysis from the University of Sussex
that found that the authors had made serious methodological errors which invalidate their work.
Nevertheless the whole thing highlighted the perfectly valid and very important challenge
of determining whether any new apparently green technology is genuinely capable of reducing the
level of greenhouse gases that are emitted into our atmosphere globally over the entirety of its
lifetime. In late 2017 another study was published in the well-respected science journal Nature. This
one used life cycle analysis modelling combined with an integrated assessment model that accounted
for the indirect greenhouse gas emissions as a result of industrial and other economic activity
modelled up to 2050 in 11 major world regions. The goal was to provide a holistic view of future life
cycle greenhouse gas emissions of low carbon technologies and power systems in the context
of a climate change mitigation regime that would keep average global temperature increases below
2 degrees Celsius above pre-industrial levels. The generally accepted way to make that assessment is
to work out total direct and indirect greenhouse gas emissions per unit of electricity produced.
Once the researchers had crunched all those numbers, which I imagine was no mean feat,
they arrived at a chart of all electricity producers in 2050
and split the emissions of each technology into direct and indirect categories. Coal and gas were
both assumed to be fully incorporating carbon capture and storage technologies by mid-century.
Whether that really happens is still open to much debate of course and even if it was achieved
the researchers still factored in a calculation for what they called imperfect CCS capture,
which to you and me means gas leaks, or fugitive emissions if you prefer the posh phrase.
Indirect emissions included land use and land use change or LULUC, upstream methane from coal
and gas, biogenic methane from hydropower, which mainly comes from stagnant water in reservoirs
behind dams, fuels for construction and daily operations, and last but not least a potentially
negative emission number from bioenergy with carbon capture and storage, or BECCS.
There's been a lot of pushback against BECCS since 2017, mainly because of concerns about
destroying existing ecosystems and biodiversity to make way for monoculture plantations to
produce the biomass, but we'll park that for the purposes of this exercise because this chart deals
specifically with emissions. The study provides a couple of useful numbers to compare to.
It says that average fossil fuel emissions from global electricity supply in 2017 were 504 grams
of CO2 per kilowatt hour generated. Average emissions from electricity production in a 2050,
2 degrees Celsius scenario will need to be only 15 grams of CO2 per kilowatt hour. Even with CCS,
coal and gas are both projected to be well above the required 2050 average,
at about 109 and 78 grams respectively. Bioenergy works out at about 97 grams, mainly as a result
of land use changes, but in theory BECCS could provide a negative offset of as much as 300 grams
for every unit of electricity produced. That's a hotly disputed number, as I mentioned earlier.
Some say the time required for crops and trees to grow sufficiently to suck all that carbon
dioxide back out of the atmosphere will be too long to provide the quoted benefit by 2050
and that carbon storage losses from tearing down existing ecosystems could cancel out many of the
benefits, so I think it's safe to say the jury is very much still out on the subject of BECCS.
Those upstream biogenic methane emissions from reservoirs plus huge emissions from dam
construction mean that hydropower, despite being heralded as a low carbon renewable, actually comes
out at just under 100 grams of CO2 equivalent per kilowatt hour in a full life cycle assessment.
Construction and daily operations do result in some greenhouse gas emissions over the
lifetime of a nuclear power plant but even so nuclear technology comes out at only 4
grams of CO2 per kilowatt hour in 2050 in this analysis. The one element of uncertainty here
is how we choose to dispose of nuclear waste in the future. Some countries are
building very large and very deep underground vaults to hold their radioactive waste material
and that kind of construction involves vast amounts of concrete steel and other materials
as well as huge quantities of energy to get it all constructed so the genuine
lifetime emissions costs of nuclear may well prove to be higher in real world scenarios.
Then we come to wind and solar photovoltaics, which you can clearly see have far lower lifetime
emissions than the fossil fuel options. Solar PV comes in at 6 grams per kilowatt hour and wind is
only 4 grams. The vast majority of those embedded life cycle emissions come from the construction
and deconstruction of the panels and turbines themselves but contrary to the claims made by
the critics of these technologies those emissions come nowhere close to equalling the enormous
amount of greenhouse gases produced by coal and gas, even with carbon capture and storage.
And as renewable technology continues to rapidly improve so those emissions will come down still
further. In 2021 a more detailed analysis of life cycle emissions from wind power was
published by none other than Bernstein Research, who describe themselves as Wall Street's premier
sell side research and brokerage firm. Hardly an archetypal environmental activist group eh?
Wind turbines use steel for their towers and both concrete and steel for their foundations,
and of course composite materials like glass fibre and carbon fibre for the blades.
Unsurprisingly then the construction using these materials makes up the vast majority of
the life cycle carbon footprint for wind power. About 86 percent in fact, compared to only one
percent for coal, which obviously does most of its environmental damage during operation.
Rather than projecting up to 2050 the Bernstein Report looked at a present day comparison
between electricity generation from fossil fuels and renewables. Coal and gas don't yet
have those carbon capture facilities in place which means emissions from coal currently run
to about a thousand grams per kilowatt hour of electricity generated and gas produces about
450 grams per kilowatt hour. Solar PV comes in at 44 grams today and the less well-known
technology of concentrated solar power produces 27 grams per kilowatt hour over its lifetime.
But both onshore and offshore wind are already challenging nuclear power as the lowest carbon
footprint technologies available even after all life cycle emissions are taken into account.
The report highlighted even more recent analysis from the turbine manufacturers themselves
which puts the life cycle emissions of wind even lower than nuclear.
Siemens Gamesa calculate life cycle emissions for one of their eight megawatt offshore wind turbines
at just six grams per kilowatt hour. Vestas reckon that a typical 42 megawatt onshore wind farm
now has life cycle emissions of between 5.6 and 7.3 grams per kilowatt hour.
A lot of that improvement comes from the sheer size of the turbines themselves and also from the
far more sophisticated and energy efficient shape of the blades. The Bernstein report shows us the
size of a typical turbine blade in 1979 against a typical turbine in 2019. Quite a difference!
And because the turbine power rating scales with the swept area of the blade. Materials intensity,
and therefore carbon footprint per unit of electricity, reduces significantly as the
blade size increases. The report concludes that, taking the whole life cycle analysis into account,
emissions from wind energy are less than one or two percent of fossil fuels. And there's scope to
get that down even more as carbon emissions from steel and cement production reduce significantly
in the coming years. Companies like Hybrit in Sweden are using hydrogen to replace coal in
the reduction of iron ore and others like Carbon Cure and Carbicrete are developing technologies
that will embed CO2 into cement rather than emitting it as part of the production process.
And recycling is improving all the time too. Eighty-five percent of expired wind turbine
materials are already recycled and the large turbine manufacturers are aiming to get that to
a hundred percent. In fact Siemens Gamesa recently launched what they claim to be the world's first
100% recyclable blade and Vestas are on track to get there by 2024. Once those technologies are
embedded in the industry and similar recycling rates become widespread in the Solar PV world
then one of the major barriers to mass adoption will have been overcome.
Now despite these findings I know this topic remains a subject of much debate and disagreement.
No doubt you've got your own views on the relative benefits and drawbacks of each energy generation
technology. If you do then why not jump down to the comments section below and share your thoughts
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