Have you ever wondered how much carbon dioxide you personally are responsible for? Between your drive to work, the food you eat, the energy used to heat and cool your house, your electronic addictions, and your lightbulbs, you probably use one heck of a lot of CO2.

 

Today, humans are responsible for dumping more than 30 billion tons of carbon dioxide into the atmosphere every year.

The average American uses about 18 tons of CO2 per year. The average person on the planet uses about 4 tons of CO2 per year. Yes, we’re way ahead of the curve. But don’t feel too bad — in Qatar they use a whopping 50 tons of CO2 per person per year.

Back to America. Eighteen tons of CO2 per year  is 18 x 1000kg CO2 = 18000 kg CO2 per person per year, about 50kg CO2 gas per person per day.

How much CO2 is that? The amount of CO2 the average American emits every day would fit into a cube with side 10ft, or a sphere with diameter 12ft.

That’s right — each and every day, the average American fills a sphere that is 12 feet across with CO2 gas (from heating/cooling, transport, food, etc). Imagine if we all had to carry our personal balloons of carbon dioxide emissions on our backs each day, and could watch them gradually inflate. Then every night we could release them into the atmosphere.


It’s all very well to know we’re personally responsible for releasing gob loads of CO2 into the atmosphere, but what can we do about it? Let’s do a little math.

DRIVING

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Roughly 19.64 pounds of CO2 is produced by burning a gallon of gasoline

The average combined fuel economy of cars and light trucks in the U.S. is somewhere around 23 miles per gallon (it changes a little – hopefully in the upward direction – every year). The average vehicle miles traveled is ballpark 12,000 miles.

12000/23 = 522 = average number of gallons of fuel used per vehicle per year

522*19.64 = 10252 pounds CO2 = 4660 kg CO2 per year

= around 4.7 tons CO2 per average car per year from burning fuel (driving an average car)

An electric car doesn’t burn any gas, but you need energy to charge the engine. If you use energy from fossil fuels, you’ll be responsible for about a ton of CO2 per year (this is covered in more detail in another post); if you have solar panels on your roof that cover your energy needs, your car electric car can be effectively powered by the sun and you can feel good about all those tons of CO2 you are no longer emitting.

HOME: ELECTRICITY

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Around 1.216 lbs (0.55 kg) of CO2 is produced per kilowatt-hour for electricity at its source (power plant; EPA 2012) and 1.307 lbs CO2 (0.59 kg CO2) per kilowatt-hour for delivered electricity (at home)

In 2011, 116.17 million homes in the United States consumed 1,424 billion kilowatt-hours of electricity (EIA 2013a). On average, each home consumed 12,258 kWh of delivered electricity (EIA 2013a).

The average American household uses 12,258 kWh per year

12258*0.59 = 7232kg CO2

= arond 7.2 tons CO2 per household per year from electricity use

The average U.S. household has 2.58 people

which means, on average, 2.8 tons CO2 per person per year from electricity use 

HOME: NATURAL GAS

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0.0283168 m³ of natural gas = 0.0103071 therm [U.S.] 1 m³ of natural gas

66,000 cubic feet per home × 0.0544 kg CO2/cubic foot × 1/1,000 kg/metric ton

= around 3.6 tons CO2 per home per year from natural gas use

-> ~0.9 tons CO2 per person per year from natural gas use 

AIR TRAVEL

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Worldwide, flights produced 689 million tons of CO2 in 2012. (For comparison, globally, humans produced over 34 billion tons of CO2 that same year.)

Flying the potential to be a significant factor in your CO2 footprint.

To get a quick estimate of how much CO2 a given flight will add: 0.1kg CO2 per passenger per kilometer traveled (this rule of thumb seems to work pretty well).

DEN-SFO 1500km = 150kg CO2 each way; 300kg (0.3 tons) roundtrip

NYC-LON 5000km = 500kg CO2. Roundtrip 1 ton CO2.

NYC-SYD 16000km = 1.6 tons CO2 each way; 3.2 tons CO2 roundtrip.

Clearly the air travel component of ones air travel CO2 footprint varies hugely from person to person. Also, just one very long-haul flight could account for almost as much CO2 as you emit from burning gasoline (driving) annually. For people who fly frequently, the air-travel portion of personal CO2 emissions could be as high as all the other personal CO2-sources put together.

FOOD

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On average, we generate between 2 and 2.7 tons CO2 per person per year from everything we eat

By switching from an average American diet to a vegan diet, you will save roughly 700kg CO2 per year in your CO2 footprint.

If you go from an average American diet to a vegetarian diet (including dairy) then you will save about 300kg CO2 per year in your CO2 footprint.

The CO2 footprint of food is complicated. It depends on how the food was grown, how it was stored, how it was transported, how it was processed. It depends on not just whether you eat meat or not, but what type of meat you eat. Lamb and beef have a huge greenhouse gas footprint, for example, while for chicken and eggs it is way less. So there are a huge number of variables associated with every item of food. The above numbers are for the typical American diet include about 27% meat. If you have 40% meat instead, this alone will increase your personal CO2 footprint by about 200-300kg CO2 per year.

Taking it to the extreme, you could imagine someone who grows all their own food organically (no pesticides) without any kind of farm machinery (tilling the fields and weeding by hand), using rainwater capture and storage to irrigate, and the food-related CO2 footprint of this person would be near zero. (Unless they saved their own seeds, there would be a small CO2 footprint associated with procuring these, and with any kind of tools used – not to mention the CO2 footprint of plastic on a greenhouse or hoophouse….)

Because food production is associated with a large amount of methane and nitrous oxide production, reducing your CO2 footprint will also reduce your output of these other greenhouses gases. Because each greenhouse gas has a different warming potential, they can all be converted to something called “CO2 equivalent”. What this means is the amount of CO2 you’d need to produce to account for the impact of a whole bunch of other greenhouse gases. The “CO2 equivalent” that you would save going from an American diet to a vegan diet is another 800kg CO2-eq. So by switching your diet away from animal products you are helping reduce greenhouse gases other than CO2.

STUFF

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The stuff we own is made someplace, and therefore comes with its own CO2 footprint. Think clothing, personal care (lotions, make up etc), iphones, stereos, kitchen goods. None of this stuff was made without burning CO2.

On average, in the US, all of the stuff we buy in one year has a CO2 footprint of about 2 tons CO2 per person per year.

So if you didn’t buy any new stuff for a year (i.e. lived with what you already have or bought used), you would save just around 2 tons personal CO2 emissions.

Because of the enormous complexity of getting a “true” CO2 footprint for each item (tracing the product all the way back to the original fossil fuels in the ground), I’m guessing that this number for “stuff” is actually a huge underestimate. But this is the number that is out there in the literature.

SERVICES

When we go to the hospital, or send our kids to school, or go to the movies, we are also using up CO2. The infrastructure we are temporarily using is responsible for burning fossil fuels to entertain us, or do surgery on us, or whatever.

The external services we use add up to an average American CO2 footprint of about about 2 tons CO2 per person per year.

SUMMARY:

The biggest contributors to the average American’s directly traceable carbon footprint are driving (close to 5 tons CO2 per person per year or 25-30% of total footprint), and their homes (gas and electric: 2.8+0.9 = 3.7 tons CO2 per year, or 20% of total footprint). Food comes in next, at 2.7 tons CO2 per person per year (15% of total footprint). We can reduce the food-related CO2 emissions by about 30% by switching from a typical American diet to a vegan diet.

If you live alone, and drive alone, your CO2 footprint will be much bigger than if you share a house and carpool.

Those who fly a lot might have an air-travel footprint even larger than driving, home, and food combined.

Both “Goods/Stuff” and “Services” come in at about 2 tons CO2 per year, which is about 10% of your total CO2 footprint each.

Then there are things that are each just a few percent of your footprint. Things like waste disposal, manufacturing of your car, home construction, public transit, etc.

Eating locally is a difficult one to get an exact number on. There’s a paper that looks into this question in detail (Weber and Matthews, 2008) and they find that transportation is only 11% of the U.S. food CO2 footprint (production is 83% and retailing is 5%). But there are other studies that estimate the transportation and storage costs to be a lot larger. And these numbers all vary with the product and the season. If Weber and Matthews are right, then eating locally would only reduce your carbon footprint by about 200kg (0.2 tons) CO2 per year. I’ve seen other studies that say if you ate exclusively local, home-grown food, you would save about 1 ton CO2 per year. Organic vs non-organic is also difficult to put an exact number on in terms of CO2 footprint. A lot of fossil-fuel use is associated with conventional agriculture.

If you want to quickly get your direct personal CO2 footprint down, the most effective way would be to get a large enough solar array to power your house, and get an electric car.

You might think you can’t afford to do this, but with the current tax rebates and lease offers in place, you might be surprised at how affordable it is becoming to reduce your CO2 footprint.

These two things – getting a solar array to cover your electric needs, and driving and electric car — would cut your direct CO2 footprint in half. Unless you are a frequent flyer, in which case it might be more like a third.

Changing your diet, recycling, buying used instead of new, etc will all have a much smaller impact on your CO2 footprint than your vehicle choice and powering your household from solar panels, and flying less long-haul flights.

One thing that concerns me about this sort of analysis is that we’re just looking at one thing: direct personal CO2 emissions. Take food for example – you might say you’re not going to switch from meat eating to vegetarian or vegan if it’s going to save somewhere under a ton of CO2 per year. But by switching diet on a massive scale, we’d not only collectively have a huge impact on the amount of greenhouse gases being produced, but we would also stop untold suffering and cruelty to the animals.

Furthermore, we wouldn’t need the massive amount of animal feed, which is grown using vast amounts of pesticides. These pesticides wouldn’t pollute our drinking water and start causing all kinds of awful effects in the smaller creatures on the planet. We wouldn’t have the enormous amounts of animal waste. And so on and so on. The ripple, or downstream effects of a change like this would be enormous – much larger than the direct effect on CO2 emissions.


So if you ever think “heck, I sure would like to do something about this CO2 problem, but what can one person do?”, here is where you start:

* Call up some solar providers and get some quotes — and if you want the no-cost option, look into leasing panels from Solar City

* Think about getting an electric car. With the deals out there now, they are surprisingly affordable to lease.

That would be an awesome start to your low-CO2 lifestyle.