Chez Doug

If we at CCR are going to give advice, we need to show that we can put our advice into action in our own lives. In this example, I use information from the time our family lived in San Diego, California riding out the pandemic (all of 2020). That is our apartment above.

My carbon footprint

When I retired from the University of Cambridge, my family began to live part of our time there and part in San Diego, California. We have spent essentially all of the past year in San Diego (the weather is too nice here to drag ourselves back to England), so that is the information used here. Also keep in mind that there are three of us in the flat - myself, my wife and our son. So I will be splitting out my own carbon footprint from that of the three of us.

Our apartment is completely electric, so natural gas use is zero.

I receive weekly, monthly and annual updates on my electricity use through San Diego Gas and Electric. Here is the most recent annual statement, reproduced through a screen capture under the My Energy part of the SDGE website. You will see that our family used a total of about 5,000 kWh (kilowatt-hours, the standard unit of electricity use) in the year, which has been a pretty typical year. My share of that for the year is 5,000 / 3 = If that pattern continued for all 52 weeks, the total consumed would be 72.89 x 52 = 1,670 kWh per year.

As I mentioned, there is no natural gas use.

Now let me go through the 7 steps you will find on the Project You page:

Step 1: My electricity use is 1,670 kWh per year. I multiply this by an emissions factor of 0.00022 tons of carbon dioxide per kilowatt-hour using the carbon intensity of power in the San Diego area. The product is 1,670 x 0.00022 = 0.37 tons of carbon dioxide per year. This product is my annual carbon dioxide emissions from electricity use.

Step 2: My natural gas use is zero, so my annual carbon dioxide emissions from natural gas use are also zero.

Step 3: My wife and I have a car which we share. The good news is that my wife and I do not drive much. We live in the middle of downtown, so we can walk almost anywhere. I checked the odometer over the past 12 months and we drove a total of 2,466 miles. But my share of this is about half, so 2,466 / 2 = 1,233 miles.

Now for the bad news. Our car is a Jaguar, and an older one at that (2003). The petrol efficiency is terrible. We average about 18 miles per gallon (I know, I know, but we look so good in the car!). This is less than half of what the average car achieves in the UK part of our life, although not much less than the average US vehicle due to the number of SUVs and trucks Americans drive. This is about 1 / 18 = 0.06 gallons per mile. Each gallon of petrol produces about 8,800 grams of carbon dioxide, so my personal emissions factor is 0.06 x 8,800 = 528 grams of carbon dioxide per mile. Now I divide by 1000 grams per kilogram, and then I divide by another factor of about 1000 to convert to tons, so I find 528 / 1000 / 1000 = 0.000528 tons of carbon dioxide per mile. Ouch. I really do need a more fuel efficient car! This emissions factor is more than twice the EU average.

My carbon footprint from the car is therefore 1,233 x 0.000528 = 0.65 tons of carbon dioxide per year from driving.

Step 4: I already included ALL car travel in my estimate in Step 3. However, I flew three times this past year, once round trip for a meeting at the American Water Works Association in DC, once round trip to Gainesville, Florida for an EPA project and once from England to San Diego (one way only). The total distance of these two round trip flights was 9,571 miles, and for the one way trip from England was 5,400 miles. My annual total is therefore 9,571 + 5,400 = 14,971 miles. I now multiply this by the emissions factor of 0.000176 tons of carbon dioxide per mile of flight to find: 14,971 x 0.000176 = 2.6 tons of carbon dioxide per year from flying.

Is that all?

My personal carbon footprint was 4.4 tons of carbon dioxide per year. But is that really all of the carbon dioxide for which I am responsible. In climate policy, we distinguish between three 'scopes' of carbon dioxide emissions:

    • Scope 1 are those completely under our control, such as running our gas boiler at home or driving our car.

    • Scope 2 are from electricity we consume from a provider (not from a solar panel on our roof), where we control how much we use but not the emissions factor.

    • Scope 3 are from things outside our control such as emissions produced by stores, restaurants, theaters, etc when we visit them, and manufacturing the goods we buy (see The Consumer section of this website).

What would be my footprint if I included Scope 3 emissions? We can get some idea of this by looking at the total carbon footprint of the city of San Diego, and especially the Appendix to the Climate Action Plan of the city (look at pages 8-11 of the 2018 update), which provides numbers on electricity and natural gas use from different sectors, including Residential, Commercial and Industrial. You will see that the Commercial and Industrial sectors produced about 1,530,900 tons of carbon dioxide from electricity and 1,550,300 tons of carbon dioxide from natural gas. So that is a total of 1,530,900 + 1,550,300 = 3,081,200 tons of carbon dioxide from these two sectors outside the home. The total population is about 1,400,000, so the per capita emissions for the average San Diegan as a result of local Scope 3 is 2.2 tons of carbon dioxide per person per year. I should add these emissions to my personal footprint.

Step 5: My wife and I watch a lot of videos through Netflix and Amazon; we are retired. My guess is we watched a total of 1,400 hours this past year. Since we both watch the video, I am responsible for half of this carbon dioxide, or 1,400 / 2 = 700 hours. Using the emissions factor of 0.0004 tons of carbon dioxide per hour of streaming, my carbon footprint from streaming is 700 x 0.0004 = 0.3 tons of carbon dioxide per year from streaming videos.

But bear in mind something I said on the Project You page. All of the streaming services are moving rapidly towards investing in low carbon, renewable energy supplies for their data centers. I suspect in the next year, this emissions factor will be less than 0.0001 tons of carbon dioxide per hour of streaming. My emissions from streaming videos is probably closer to 0.1 tons of carbon dioxide per year, and likely to fall further in 2021.

Step 6: I do not routinely weigh the garbage we throw out. We are good about recycling (Vantage Pointe makes that simple) and my wife is a great cook who uses only fresh ingredients. The average American throws away about 5 pounds of total waste per day. I have made some measurements on a few days this year, which I took to be representative days, and find that our family of three throws away an average of 6 pounds of total waste per day, of which about a third is biodegradable. So for me personally, that is 0.66 pounds per day of biodegradable waste, or 0.0003 tons per day or 0.12 tons per year. The emissions from this part of my life is therefore 0.12 x 1.02 = 0.12 tons of greenhouse gases per year.

Step 7: Now I add all of these 6 steps together. That sum is 0.37 + 0 + 0.65 + 2.6 + 0.3 +0.12 = 4.0 tons of carbon dioxide per year (3.8 tons of carbon dioxide per year if the more up to date emissions factor for streaming videos is used).

Notice that 65% of this is due to air travel. That is where my carbon reduction efforts must begin. If I took that out, I would be below the 2 tons of carbon dioxide per person per year number that is the global average target! So there is hope for us all. Next in line is my footprint from driving. We love our Jaguar, so our strategy is first to reduce the miles we drive each year. That is feasible because we are retired and we have already seen the world. So I am committed to reducing miles driven by 10% next year. And then there is that footprint from streaming movies. Our hope there is that Netflix and Amazon (and Google and You Tube) all move to much lower carbon power supplies. They are well on the way to doing that, and we will update these numbers as that happens. Check back in 2021 and see what I have done to my footprint.

It is even more complicated

I have not told you the full story. The apartment complex in which I live has meters on the electricity used inside the apartment, and that is what I have described so far. That is what SDGE bills us for. But the hot water is produced in a communal water system and pumped to my apartment. And some of the heating and cooling steps take place first in a communal system and then a fluid is pumped to the apartment where it is are used in a heat pump. So there is a 'hidden energy use' in my life. Most of the energy for heating and cooling still is done by the heat pump in the apartment, so that part of my footprint is already probably close to the total value. My use of hot water, however, is not included in that total.

How large could the water heating contribution be, added onto the 1,670 kWh/year I told you in Step 1? To get an idea, the average home electric water heater consumes about 3,300 kWh/year. There are three of us, so my share is 1,100 kWh/year. Therefore, my estimate of my total electricity use for everything combined is about 1,670 + 1,100 = 2,770 kWh/year.

Notice that hot water alone contributes about 1,100 x 0.00022 = 0.25 tons of carbon dioxide per year to my personal carbon footprint. So instead of 4.0 tons of carbon dioxide per year, let's make that 4.3 tons of carbon dioxide per year from the Scope 1 and Scope 2 emissions. Looking again at the text box on Scope 3, I will add in another 2.2 tons of carbon dioxide per year, for a total (Scope 1, Scope 2 and Scope 3) of about 6.5 tons of carbon dioxide per year. Even if I reduce my flying to zero, I clearly have another factor of two reduction to achieve by the other components of my footprint, where about half of the non-flying part is from Scope 3. This is another reason why carbon reduction must be a community effort.

A side note

If I had done the same calculation assuming we lived in Cambridge this past year, my carbon footprint would have been a little above 9 tons of carbon dioxide per year, counting flying. This is because the weather there is not at all as good as here in San Diego, so there is a lot of heating to be done in our home. Also, when I was still a professor at the University of Cambridge, I flew a lot more often to countries around the world to lecture them on reducing carbon dioxide. There were years when my footprint only from flying was more than 10 tons per year. I imagine St. Peter and I will be having a conversation about that at some point. :)

Other energy uses

One strategy to reduce my carbon footprint would be to replace the appliances in our home with high efficiency ones. However, the fridge/freezer, stove, oven, microwave, dishwasher and washer/dryer are all supplied by the owner of our building. I do not control these purchases. And Vantage Pointe already uses reasonably efficient GE profile appliances. The more energy efficient ones would not reduce electricity use of appliances by more than 10%. Appliances account for about 45% of my electricity use, so my carbon emissions from Step 1 would only decrease by 5% overall, going from 0.37 to 0.35 tons per year.

The Energy Information Administration produces a good summary of electricity use in US homes, divided by region. Their data show that the average electricity use for apartments in the West is about 4,580 kWh per year. So our value of 5,208 kWh is slightly above the average. However, we have three people in the home, not the average of two, and my wife and I are retired so we are home all day.

I have not yet spoken about lighting or television. I have examined all of the bulbs in our house, and determined the number of hours per year each is on. My estimate is that lighting contributes about 300 kWh/year of the total 5,208 kWh/year. If I switched entirely to LED lights, I could reduce this 300 kWh/year to perhaps 200 kWh/year (some of the lights are already LEDs). So that is a reduction of 100 kWh/year or 0.02 tons of carbon dioxide per year for the house, or slightly less than 0.01 tons per year for me alone. The challenge is that the ceiling lights are all maintained by the apartment management, not by me. I would need to get them to change the bulbs.

As to the television, I mentioned that we watch a LOT of streamed movies. I have measured our 'watch time' as about 6 hours per day or 2,190 hours per year. Our television consumes about 100 watts or 0.1 kilowatts at any moment it is on. So that is a total of 2,190 x 0.1 = 219 kWh/year. My share is 110 kWh/year or 0.025 tons of carbon dioxide per year. But for the household, our son also has a TV of similar size. I estimate his consumption is about 180 kWh/year, for a total of 400 kWh/year for the two TVs combined.