TheLittlestGuy

I’m house-sitting right now and I have had some time to research and write. One article about carbon emission factors has expanded and become several articles. I’m currently using a halogen desk lamp so I can see. Allow me to crunch some numbers on this 50 Watt lamp.

In a previous article about carbon emission factors, I determined that my little lamp is producing about 45 grams of CO₂ for every hour that it’s on. The Trees for the Future website claim that for $0.10 a “fast-growing, beneficial, permanent” tree can be planted to remove “about 50 lbs. of CO₂ from the atmosphere each year” for about 40 years. (http://www.treesftf.org/about/cooling.htm). If true, about 22,500 grams of CO₂ can be absorbed from the atmosphere a year from one tree. My lamp produces about 45 grams of CO₂ an hour.

That’s great news for us because if I plant one tree then I can run this light a lot without adding any net CO₂ to the atmosphere! Well, kind of. If I plant one of these trees then I can run this 50 Watt light for 500 hours a year (22500 g / 45 g/hr = 500 hr). It’s already been on about 10 hours the last few days as I’ve been researching and writing at my temporary desk. If I kept up this pace of writing, then it wouldn’t take me long to hit that 500 hour mark. Okay, so my one plant doesn’t get me as far as I’d like. But that’s only a small part of the problem. There are two bigger problems. 1) I haven’t planted any trees or large plants this year. 2) I currently have a lot more stuff on right now than this one lamp. There are actually 19 other lights on – or there were until I walked through the house, counted, and turned off a few. I bet if you stop reading this right now and walk around your house or apartment (or wherever you happen to be) you’ll find tons of stuff consuming power.

another problem

Much of the energy produced to power this 50 watt lamp is wasted in the form of heat anyway. I didn’t turn this lamp on to heat the room. I turned it on for light. Lamps are not very efficient ways to heat houses – heaters are much better at this. During hot summers this is actually a huge pain. We turn lights on so that we can see and those lights then increase the temperature of the air in the room and also make us feel warmer (like the sun’s rays warm us up when we go outside). Then we turn our AC units on so that we are comfortable. We’re using energy for the lights and the AC unit. If our lights produced less heat, then our AC units would run less often (and actually last longer too) saving us money, conserving rapidly depleting fossil fuels, and helping to reduce CO₂ emissions. That’s why I have replaced all the lights that I use often with low energy lights bulbs (link!). These lights are more efficient because they produce much less heat than this halogen lamp – which is actually hot enough to sizzle when I touch it with a wet finger. Common sense tells me that the lamp is at least 100 degrees C and that means a lot of energy is being wasted as heat.

so what’s the lesson?

First, we have to conserve energy. We can do this by running things less or by making them more efficient. This 50 watt lamp (and more of the lights in this house) should be replaced with energy saving bulbs. Many of the lights in this house should be on timers (or better yet, light sensors) so that they are on only when they need to be. Phantom loads should be found and minimized. There are tons of little things we can do to use a little less energy, and lots of larger things we can do to save a lot more energy. The less energy we consume the more time we have to find sustainable alternative energy sources and the less we pollute our planet.

Second, we have to find ways to remove CO₂ from the atmosphere and to offset our carbon production. So seriously, go plant a tree this weekend. Have your kids help you and explain to them why the little things add up.

The carbon emission factor for a particular fuel is the amount of carbon released per amount of energy produced. Fuels are combusted to release their energy. In general, a fuel source, oxygen, and some initial energy (often heat or a spark) are required to start a combustion reaction. Currently, most of our fuels are some sort of hydrocarbon (a molecule that is made of hydrogen and carbon atoms). The bonds of these molecules must be broken (which is why the heat or spark is required) and then these hydrogen and carbon atoms react with oxygen to form CO₂ and H₂0. The formation of these new bonds releases energy that we can capture and use to do work (like move a car from one place to another or to heat and light our home).

The carbon emission factor of a fuel simply tells us how much carbon will be released per unit energy. The less carbon that is released when we produce a certain amount of energy the less CO₂ we produce and the less greenhouse gases there are to cause global warming and climate change. Since reducing greenhouse gases is important, carbon emission factors are important too.

Below are the carbon emission factors for several common fossil fuels. The lower the number the less carbon is released per unit of energy released.

Natural Gas: 0.46 kgC/watt-year
Oil: 0.60
Coal: 0.77
Wood: 0.89
(Watts, Robert, Innovative Energy Strategies for CO₂ Stabilization, 32)

math & science warning

Lets take a brief look at how this number is calculated. I’ve chosen to use coal as an example. One popular type of coal, gas coal, produces about 35,000 Joules per gram according to Wikipedia (http://en.wikipedia.org/wiki/Coal). 85% of this type of coal is made of carbon.

0.85 carbon	1 gram coal	1 kilogram	1 Joule	31,536,000 sec
1 coal	35,000 Joule	1,000 grams	1 Watt-sec	1 year

= 0.766 kilograms Carbon/Watt-year (compared to 0.77 kilograms Carbon/Watt-year above)

I hope I didn’t lose you there…that’s about as scientific as I’ll get in this article. If that didn’t make sense then you can decide whether you want to believe me or you can take the time to prove that coal’s carbon emission factor is 0.77 for yourself.

Whether you desire to prove this to yourself or not, what this means is that over the course of a year, coal can produce 1 Joule of energy per second for an entire year and produce 0.77 kg of Carbon over that year. 0.77 kg of carbon is equivalent to 1.425 m² of CO₂ gas.

That’s not a very easy fact to visualize so let me work with a more concrete example. The very bright halogen light that I’m using as a desk lamp currently has a 50 Watt light bulb in it.

50 W * 1hr	1 Joule/s	60 mins	60 sec	1 g coal	0.85 g carbon	44.01 g CO2
	1W	1 hr	1 min	35,000 Joule	1 g coal	12.01 g carbon

W = Watt

g = gram

= 16.02 gram CO₂ is produced by my 50 Watt lamp every hour. This number is not quite accurate because it doesn’t account for the energy lost when combusting coal. Efficient coal plants run at 36-38% efficiency (http://en.wikipedia.org/wiki/Fossil_fuel_power_plant). New designs may allow coal plants to operate with efficiencies between 40-48%. What this means for our 50 Watt light bulb example is that three times as much coal may be required to power the light bulb than calculated above.

back to basics

So let’s say that 45 grams of CO₂ are produced for every hour a 50 Watt lamp is on. This is kind of difficult to imagine so let me put it in more concrete terms. One US nickel has a mass of about 5 grams. So take about nine nickels and that is the approximate mass of CO₂ produced by having my light on for one hour. In order for this CO₂ to be removed from the atmosphere, a plant (or some other kind of phototroph) must use photosynthesis to convert the sun’s energy into chemical energy. Photosynthesis uses light, CO₂, and water (CO₂ and water are products of a combustion reaction) to make glucose, a sugar which is often converted to a carbohydrate like starch or cellulose (for energy storage/transport or structural reasons).

In another article I do the math and figure out how many trees it would take to get this CO₂ I just produced out of the atmosphere (carbon offsetting). The short answer is that if I plant one tree I could run my 50 watt lamp for 500 hours a year without having a net increase on the CO₂ in the atmosphere. But there are two problems: I didn’t plant a tree and I have a lot more stuff consuming power than this one lamp right now.

conclusion

So before I get too far off the topic of carbon emission factors, let me wrap things up so you can read about carbon offsetting. Carbon emission factors are important because they tell us how much carbon we’re releasing when we combust fossil fuels to get energy. The shorter the hydrocarbon (link), the less carbon is released per unit energy produced. [I may explain the fairly complex chemistry of why this is in another article.] So natural gas (methane primarily) releases less carbon per joule of energy than oil, which releases less carbon than coal, which releases less carbon than burning wood. Most of the United States power comes from coal, of which the US has vast amounts. Coal has a fairly high carbon emission factor, which means that if we were to combust natural gas instead of coal we could release less CO₂ and still produce the same amount of energy. This is important for developing countries like Chine, which is currently building huge infrastructure of coal plants. China could help out the climate change situation a great deal by using fuels that have lower carbon emission factors.

Oh yeah, I forgot to mention that most renewable energy sources have carbon emission factors of 0. That’s because they don’t release any CO₂ into the atmosphere or because they release the same amount of CO₂ that they consumed when they were created. Ethanol is made from plants which consume CO₂. Then the ethanol is combusted and releases CO₂ back into the atmosphere and more plants are grown.