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Question: which has a greater embodied energy: a cup of tea/coffee or a can of Coke (or Pepsi, or other caffeinated soft drink) -- or maybe some other stimulating drink? I have made some estimates of my own, but there are some areas I haven't been able to figure out e.g. transportation, and I am looking for someone who may be better informed.

Factors

Cup of tea/coffee:

  1. Production of packaging
  2. Transportation from country of origin
  3. Heating water

Can of Coke:

  1. Production of packaging
  2. Transportation of raw ingredients
  3. Manufacture
  4. Transportation of product from the factory

My estimates:

Boiling one cup of tea: 0.11 kWh

500 g water (minimum amount for typical kettles)
Q = mcΔT
Q = Heating required
m = Mass of water = 0.5 kg
c = Specific heat capacity of water = 4.18 kJ/kgK [1]
ΔT = 85 Kelvin
Q = 178 kJ = 49.4 Wh
Efficiency of electrical power grid (e.g. in the US) [2]:
Generation: 40%
Transmission: 94%
Net effy = 38%

So total energy cost of a cuppa I'd reckon is 413 kJ = 0.110 kWh

Aluminum can production: 0.28 kWh

14.9 g : Mass of an empty can [3] 
183e9 kWh : US total Aluminium industry energy consumption (2003) [4]
9.6e6 tonnes : US Aluminium industry raw materials used (2003) [4]

This gives 19.1 kWh/kg, or 0.28 kWh/can

Manufacture: ?

Not sure about energy required in manufacturing coke or blending tea.

Transportation: ?

Suspect transportation is fairly negligible in both cases as neither are perishable so probably transported by sea and road, which is relatively efficient.

References

  1. “Water - Thermophysical Properties.” [Online]. Available: https://www.engineeringtoolbox.com/water-thermal-properties-d_162.html. [Accessed: 23-Jan-2018].
  2. “Energy Efficiency in the Power Grid - NEMA,” mafiadoc.com. [Online]. Available: https://mafiadoc.com/energy-efficiency-in-the-power-grid-nema_59842ba91723ddcf69a39c32.html. [Accessed: 23-Jan-2018].
  3. “How much does an empty soda can weigh?,” Reference. [Online]. Available: https://www.reference.com/food/much-empty-soda-can-weigh-e7e0417d7a8ec29. [Accessed: 23-Jan-2018].
  4. E. Efficiency, “US Energy Requirements for Aluminum Production,” 2007. Available: https://www.energy.gov/sites/prod/files/2013/11/f4/al_theoretical.pdf
  • 3
    My guess is that the health impact of Coke would mean the downstream healthcare costs outweigh any production costs. – Highly Irregular Jan 24 '18 at 0:47
  • Hmmmm... Not sure how you would quantify that! Besides, given that 1.8 billion coca cola drinks are sold a day [statisticbrain.com/coca-cola-company-statistics/], can we really pin down healthcare costs on a single beverage? I mean this question seriously, please respect it. – Arty Jan 24 '18 at 23:42
  • I do respect it... I still upvoted :-) – Highly Irregular Jan 25 '18 at 1:12
  • 1
    I think your estimate for boiling the water is slightly out - a bit of googling suggests that the average temperature for tap water is around 7-15C (say an average of 10) depending on location and season - so the delta would be 90K, not 75. I'd also suggest there is a much bigger transport difference, as tea can be packed quite densley - I'd say a 100g pack of tea is about the same volume as one single tin can – Nick C Jan 25 '18 at 13:07
  • @NickC Agreed, the temperature difference is quite rough and ready. I haven't take into account the variation in packing density as the statistics I have only give the amount of energy required per tonne, averaged over all vehicles I guess. So if you have a little van which uses more fuel per unit mass than a huge lorry then we are averaging over the two. I guess an advantage with tea is that it is often transported in dry form, so less energy in transport (unless it is Ice Tea)! – Arty Jan 25 '18 at 21:40
2

TL;DR -- The best option, per liter, is tea. Soda is about twice as "bad," and coffee is two times worse than that.


To compare the environmental impact of various beverages we need to perform a life-cycle assessment. From Wikipedia:

Life-cycle assessment (LCA, also known as life-cycle analysis, ecobalance, and cradle-to-grave analysis) is a technique to assess environmental impacts associated with all the stages of a product's life from raw material extraction through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling.

In 2010, Nestle Waters North America commissioned a study to look at the environmental impact of various beverage choices. They hired Quantis to do this study. According to their website, Quantis

[...] guide[s] top organizations to define, shape and implement intelligent environmental sustainability solutions [...] We are [...] sustainability’s scientists, experts, strategists, innovators and visionaries.

The study is titled "Environmental Life Cycle Assessment of Drinking Water Alternatives and Consumer Beverage Consumption in North America", and looked at 13 popular beverages in North America, including coffee, tea, and soda. The report includes new research as well as reviews of existing studies, and provides the following chart:

enter image description here

A table showing the values per liter (and references) is provided later in the report:

enter image description here

Unfortunately, this table shows the weighted average of hot tea and iced tea. From the chart though it's clear that hot tea has a much lower overall carbon footprint.

Conclusion: hot tea is the most sustainable pick-me-up. A can of coke is about twice as bad, and a cup of coffee is about four times worse.


Corroboration

The previous version of this answer had a few different sources that corroborate the chart/table above, without the nice comparison:

  • Here's a little tidbit to go with this answer. The studies for tea and coffee consider just the tea/coffee, with no milk. A large (476 ml) cup of tea without anything extra has a footprint of 317 gCO2. Adding a tiny (12ml) pot of dairy milk increases the carbon footprint by 17 g to 334 gCO2. A more realistic amount (say one part milk to four tea) and this jumps to 387 gCO2 per cup. A large Nespresso capuccino has a footprint of around 460 gCO2/cup (980 g/L including the froth). If you can't stand black coffee try non-dairy milk (330 g CO2 for soy) or try a medium cup (209 gCO2 for 257 ml) – Arty Oct 5 at 13:53
  • Removed my previous answer. Typos – Arty Oct 5 at 13:53
1

Sustainability isn’t just about energy. It also involves other pollutants and water usage.

Tea uses 100 times the volume you drink to be produced. [1]

And according to this [2] it takes 65 times the volume of water for one litre of Coke. But that doesn’t take into account the mining of the metal for the can, nor the transport of the Coke can (water for your tea is local), or the recycling required to melt the aluminium can again. Whereas tea is generally drunk from a reusable cup.

My guess is that the Coke is worse for the environment overall.

[1] https://www.huffingtonpost.com/2014/10/13/food-water-footprint_n_5952862.html

[2] https://www.quora.com/I-have-read-that-it-takes-9-liters-of-water-to-produce-1-liter-of-Coca-Cola-Is-it-true

  • One must also consider the environmental impact of High Fructose Corn Syrup, and all of the environmental impact that big agribusiness has on our watersheds. Like the dead zone in the gulf, which is caused largely by fertilizer runoff. – flummingbird May 30 '18 at 15:44

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