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An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Posts Tagged ‘Earth Hour

Earth Hour, candles and carbon

with 93 comments

There’s one thing in particular that bothers me about Earth Hour – these people who electric lights and then go and light up candles, and think that they’re helping do something about anthropogenic forcing of climate change.

The widespread practice of misguided eco-Luddites turning off their lights for Earth Hour and burning candles as a source of light is grossly misguided and actually contributes to increased carbon dioxide emissions.

Yes, I know candles are nice and romantic – but you’re taking paraffin wax, in the form of a candle, and burning it, very inefficiently, at a low temperature. This stuff is pure hydrocarbon – it’s a heavy alkane fraction distilled straight off crude oil. This stuff is getting so scarce that nations are prepared to go to war just to secure it, remember?

A candle flame burns at a low temperature – so it’s a thermodynamically very inefficient source of energy – and most of the energy released in a candle is wasted as heat, anyway.

Even if 80% of your electricity comes from coal and fossil fuel fired power stations, as it does in Australia, burning candles is very polluting and certainly very greenhouse gas and carbon dioxide emissions intensive, even more so than electric lighting.

If you need to do something that requires light – then leave an electric light on – just one. It’s far more efficient, less carbon dioxide emissions intensive and better for the environment – not to mention much safer than using hazardous candles.

If you want the romance of a candle, try looking for candles that you are certain are made from pure “carbon neutral” beeswax or tallow – not from crude oil in the form of paraffin wax.

Can’t we just put science, reason, rationality, education and reason ahead of trendy politics and trendy dogmas – before it’s too late?

What Earth Hour should not be about is the notion that we want to have a civilisation without artificial lighting – this is absolutely ridiculous. Lighting up the darkness was one of the most useful technological achievements in human history – why would we give that up?

Using electricity for lighting is far more efficient and environmentally sound than the primitive technologies, burning fossil fuels dirtily, at ambient pressure and relatively low temperatures, that came before electrification.

The use of electricity, and the use of electric lighting, is part of our way of life, in a developed, technological first-world society – I, for one, am not prepared to give that up, not the least because we don’t have to.

Light bulbs don’t produce greenhouse gases – burning fossil fuels to generate electricity does.

Let’s focus our efforts on moving away from fossil fuel based electricity generation, and expanding the use of non-greenhouse gas intensive hydroelectricity, nuclear energy, and wind energy, to solve our problems with anthropogenic greenhouse gas emissions.

Earth Hour should be about doing everything that you can to reasonably, sensibly limit your demand for electricity – and we can do this every hour of every day, of course. It makes sense for everyone – after all, you pay for the electricity.

I guess I have a problem with the idea that Earth Hour symbolises something.

It might symbolise something, but it doesn’t actuallydo anything.

The only thing it symbolises is primitive society.

I’d much rather see people spend their Earth Hour doing something that really does count for something.

Instead of spending your Earth Hour bearing with an uncomfortable, dark lifestyle, use that hour to think about the things that we can all do every day to limit electricity consumption, that we will actually bother to do every day, that are compatible with the fact that, yes, in our developed first-world society, we actually use electricity, and we work after the sun goes down. Think about the things that are compatible with our sensible lifestyles in the developed world, and do them, and it works out better for everybody!

Now, let’s consider just how much, quantitatively, this use of candles during Earth Hour is responsible for increased emissions of greenhouse gases.

Postulate I: A typical candle produces about 13 lumens of visible light, from a total power output of about 40 W, most of which is heat.
Postulate II: A 40 W electric incandescent light bulb consumes 40 W of electric power, and produces approximately 500 lumens of visible light output.
Postulate III: The overwhelming majority of candles are made from petroleum, in the form of paraffin wax. Paraffin wax has a heat of combustion of approximately 42 kJ/g, and can be assumed to consist, chemically, entirely of pentacosane – \mathrm{C_{25}H_{52}}.
Postulate IV: The average greenhouse gas emissions intensity for electric power generation in Australia is about 1000 g \mathrm{CO_{2e}}/kWh, and electricity is transmitted with transmission losses of about 7%.

\mathrm{C_{25}H_{52}(g)\ +\ 38\ O_{2}(g)\ \to 26\ H_{2}O(g)\ +\ 25\ CO_{2}(g)}

\mathrm{M(C_{25}H_{52})} = 352.68 g/mol;

\mathrm{M(CO_{2})} = 44.0 g/mol.

Thus, we know the emission of carbon dioxide from burning candles:

\mathrm{\frac{40\ W/candle\ \cdot\ 25\ mol/mol\ \cdot\ 44\ g/mol\ \cdot\ 3600\ s/h}{4.2\ \times\ 10^{4}\ J/g\ \cdot\ 352.68\ g/mol}\ =\ 10.69\ gCO_{2e}} – per candle per hour.

And the rate of carbon dioxide emissions from the electricity generation corresponding to the use of 13 lumens worth of lighting – the equivalent of one candle – for one hour:

\mathrm{\frac{13\ lumens/candle\ \times\ 1000 g/kWh\ \times\ 107\%\ \times\ 40\ W\ \times\ 10^{-3}\ kW/W}{500\ lumens}\ =\ 1.11\ gCO_{2e}} – per candle-equivalent of electric light per hour.

Therefore, for every candle that is burned to replace electric lighting during Earth Hour, greenhouse gas emissions over the course of the one hour are increased by 9.6 g of carbon dioxide.
If the light output from a 40 W light bulb was to be completely replaced by candles, this will lead to the emission of an extra 295 grams of carbon dioxide per over simply using the electric lights – if the equivalent of one thousand 40 W bulbs are replaced by candles, that’s an extra 295 kilograms of \mathrm{CO_{2}} emitted.

In places where a greater proportion of the electricity supply is generated by nuclear energy or hydroelectricity, this increase in greenhouse gas emissions is even larger.

Written by Luke Weston

March 31, 2008 at 5:13 pm