Recently there was a report on CO2 contribution of a single tweet
Twitter developer recently gave a talk at Chirp entitled “Energy/Tweet,” where he claimed that a tweet consumes approximately 100 joules of energy (0.02 grams of CO2 emissions)
Note that this (and my calculation below) is CO2 allocation and not true incremental CO2 cost computation. CO2 emissions from the data center, network, tweep’s computer are all sunk. If they are not tweeting what other activity could they be doing – compared to that the incremental contribution to CO2 from a single tweet could be much lower.
How does this compare to a bottle of beer?
I used the data from New Belgium Brewery, it produces 330,000 barrels of beer a year and according to their data this process produces about 5000 metric tonnes of CO2.
(1 beer barrel is 31 gallons, 1 gallon is 128 ounces, and 1 bottle is 12 ounces)
If I can do a simple cost allocation and distribute the 5000 metric tonnes across 109.12 million bottles of beer, it is about 46 grams of CO2 per bottle. This is just manufacturing alone. If we can triple this for refrigeration, shipping and retail sales, it is about 125 grams per bottle.
So 1 bottle of beer is equivalent to 6250 tweets for CO2. I am not sure about the buzz (no pun) equivalence between a tweet and beer.
Compare this to EPA numbers on driving a car. On the average 12,000 miles add 12,100 pounds of CO2, converting to metric units, it is about 450 grams per mile.
If you want to find the CO2 impact of your meals check out the LowCarbon Meals calculator that Siel of LA Times points out.
In a previous post I calculated the approximate CO2 footprint of a bottle of beer to be 125 grams. The calculation did not look at the CO2 share of raw materials (cultivation, storage, transportation) and used the average CO2 output of the entire brewery (New Belgium Brewery) instead of calculating for individual process steps.
The New York Times has a nice calculation for a bottle of wine, shipped from France and shipped (to New York) California. The respective numbers for France and California are, 1371 and 2514 grams. The breakdown is as follows:
The transportation numbers for California are higher due to coast to coast shipping. If we take the average then it is about 700 grams and for local consumption within California it is about 50-75 grams (guesstimate).
To put this in perspective, a bottle of French wine is equivalent to driving 3 miles and a bottle of California wine is about 3.5 to 5.5 miles. So if you biked to work for an average of 6 miles round trip and finished the evening with a bottle of French wine, your saving from not driving th car is cut in half.
The transportation costs for beer is lower because most breweries are located close to the market they sell. The numbers however may well be an underestimate.
In both the Beer and Wine CO2 per bottle calculations, the numbers are average. That is the total numbers are distributed among the quantities produced. But most of these CO2 costs (manufacturing, transportation, storage) are fixed costs and not marginal costs, producing and consuming one more bottle of beer does not increase CO2 cost by another 125 gram. But the numbers do add up if everyone cuts just one bottle of beer per week.
For driving, the 450 grams per mile is marginal cost, so even if you are the only one who chose not to drive there are savings.
I wonder what is the CO2 impact of drunken driving!
One of my classmates started a project LiveClimate.org that lets you offset your CO2 by donating money to specific projects that “remove CO2 from the atmosphere for you”.
I am very much impressed with the site’s design, flow and integration. They use a shopping cart to add your donations to specific projects, a clever use of shopping cart and have an amazing photos widget. As a great example of user interface design, their footprint calculator links directly to the “Shopping Cart”. While they ask you for a donation of $21 per tonne of CO2, they are very accommodative, instead of typing your carbon footprint, you can type in the amount you want to donate.
There is no excuse these days to have a mediocre web design. I really would hire the people who did their website design.
I am still not convinced about the impact of CO2 emissions on global climate change. However I decided to do a comparison of CO2 footprint of Walmart vs small stores. Since there are so many discussions around supporting local mom and pop stores vs. big box retailers, I wanted to do a comparison of these two along just this one dimension (commemorating the Earth week). To make it an even comparison I used CO2 tonnes per dollar of sales and per employee.
I assumed that the retail stores are on the average 4000 square feet and owned one car driven for 20,000 miles for business purposes. Since no free calculator for small business is available, I used an estimate that mirrors an household of similar size and people. Hence I underestimated the electricity spent on large refrigerators, continuous lighting, store display signs and the CO2 impact of distribution of goods to the stores.
For Walmart, the published data says $19.2 million tonnes and it includes all their trucks, corporate jets, stores and corporate offices.
The total US retail sales is $4.2 trillion (retailindustry.about.com).
The single stores’ share of total retail sales is 50% (same source).
US Census data says, the number of retail stores with less than 10 employees as 796,000. These numbers give a very high annual per-store sales (about $2 million). This should be treated as an overestimate of actual numbers.
Here is the comparison. On a per dollar sales, Walmart looks about 50% as bad. On a per employee basis, Walmart is way better.
- For small stores, the CO2 footprint is underestimated and the annual sales numbers are overestimated.
- Walmart’s numbers include the entire corporation and non retail related activities.
- Walmart has large economies of scale and can ride their experience curve to make large positive impact on their CO2 footprint.