Until this week, at my program at Yale they provided us with disposable K-Cups to make coffee. A certain crowd agitated, and without warning they decided to stop providing disposable K-Cups. Instead they had roast coffee grounds, the reusable K-Cups, and pour-over coffee makers, with discussions ongoing about getting a regular coffee maker. I am perpetually grumpy and anti-authority, and was upset about this change. I’ve put my analysis below, but as far as I can tell disposable K-Cups are the most efficient method of producing coffee man has ever created. It’s stunning. They are so miserly with coffee, and coffee is such an energy-intensive crop (especially when you consider coffee being drunk in New England with the transportation energy included) that the extra roast coffee grounds required to make coffee for literally any other method (including, importantly, reusable K-Cups) more than offsets the carbon cost of the plastic in K-Cups.

This is an important point when it comes to environmentalism. You have to consider the whole picture. Single-use plastics are bad but they don’t exist in a vacuum; if they are replacing something else, what is the alternative? By switching from disposable K-Cups to another coffee brewing method, we’ve eliminated bright white plastic from sitting in our garbage can, but we’ve replaced it with an even greater amount of carbon dioxide we just release into the atmosphere. That carbon dioxide is easy to ignore though, because it is invisible and happens far away from us (or at least a bit down the road). People don’t have a good grasp on the fact that an electric kettle is a 3kW device that sucks down just gobs of power, and that’s because they don’t have a good grasp on how many of the systems we just take for granted in the Western world actually work.

To make a vaguely related point, this is why I get upset when people talk about nuclear waste. Nuclear waste is bad, I agree, but it is better than CO₂. Dealing with nuclear waste is a relatively easy technical problem; you just bundle it up and stick it in a hole. It’s easy to transport and it just sits there. But people can see it, and have to do the actual transporting. It’s easier to be in favor a natural gas power plant in your backyard because the only waste that thing generates is invisible gasses that just float away.

The takeaway here is not that K-Cups are good for the environment. Turns out coffee is bad for the environment. But if you’re going to drink coffee (and participate in all the other terrible, environmentally unfriendly aspects of a modern Western lifestyle), then it seems that disposable K-Cups are literally the least bad way to do it.

My Analysis of the Carbon Footprint of K-Cups:

Disposable K-Cups: Each K-Cup is made of 4g plastic and 10g roast coffee (numbers range from 3-4g of plastic, and 5-11g of coffee).

Reusable K-Cup: Instructions call for using 2tbsp of coffee, which is 16g.

Carbon Footprint of Plastic: The “recyclable” K-cups (the latest ones) use polypropylene (PP). According to EPA estimates, each short ton of PP produced results in 3.02 metric tons of CO₂ production, which is equivalent to 3.33g of CO₂ production for 1g of PP produced.

Carbon Footprint of Coffee: Estimates here are hard to get. The most complete study was for coffee produced in Costa Rica and consumed in Europe. If you subtract consumption (brewing the cup, producing the filter), they estimate 2.83kg of CO₂ for every 1kg of green coffee. For every 16oz of green coffee you generally produce 12oz of roast coffee, so you produce 3.77g of CO₂ for 1g of roast coffee grounds. That is on the low end of estimates; other sources I found say 5.5g to 11g of CO₂ for every 1g of roast coffee. Estimates for the carbon footprint of coffee are always going to be all over the place because it will depend on where they come from (our local roaster sources coffees from as close as Mexico and as far away as Sumatra) both due to transportation costs and production methods. The coffee plantation I lived next to had center-pivot irrigation and that had to consume tons of energy. The sources cited before also note the huge impact fertilizer use has on carbon footprint.

Carbon Footprint, Disposable vs. Reusable K-Cup: A Disposable K-Cup has a carbon footprint of 55.0g CO₂ (13.3g from the plastic, 4g of plastic, 37.7g from coffee). The Reusable K-Cup has a carbon footprint of 60.3g CO₂ (all from the coffee). So net, a Disposable K-Cup has a lower carbon footprint than a reusable K-cup. This is a low-end estimate; the difference gets much worse for Reusable K-Cups if we use the higher coffee carbon footprint from the other sources. Coffee is such an energy intensive crop and Disposable K-Cups are such an efficient coffee brewing system that the additional plastic in a disposable K-Cup is more than offset by the additional coffee in a reusable K-Cup. You even throw away less trash; the Disposable K-Cup weighs a total of 14g, but the Reusable K-Cup uses 16g of coffee, which also just gets thrown away (we don’t have a compost bin or anything). The major assumption in this is that the transport and packaging costs of K-Cups and roasted coffee is the same. I think this is a safe assumption because the K-Cup manufacturers have economies of scale, and when the K-Cups are delivered it is via very efficient delivery systems. The smaller scale of operations of the local roaster we get our coffee from likely means they are less efficient in their roasting and packaging operations and in their delivery systems. K-Cups are so efficient that Bloomberg credited the rise in K-Cup use over traditional coffee pots for a downturn in worldwide coffee demand. I also did not include the energy estimates for brewing the cup of coffee because I assume this is the same for disposable and reusable K-Cups, but this is significant for other brewing systems.

Waste in Other Brewing Methods: It takes a large amount of energy to heat water. At Yale, the electricity comes from the Central Power Plant (CPP), which uses natural gas and has a 20% thermal efficiency (20% of the thermal energy at the power plant is converted to electrical energy, which is per the tour I took at the beginning of the semester and is normal for turbine systems). 12oz of water weigh 0.78lbs, 1 BTU is the energy required to raise 1lbs of water by 1°F, and 53.07 kg CO2 is produced for every 1 million BTUs from natural gas. Thus, heating the water for one cup of coffee produces 29.4g CO₂, which is equivalent to the plastic in just under two disposable K-Cups:

(212-70°F)*0.78lbs*(1BTU/°F-lbs)*(53.07kgCO₂/1,000,000 BTU)*(1000g/1kg)/20% = 29.4g CO₂

The takeaway from this analysis is that a major inefficiency in other types of brewing systems is wasted energy from heating extra water. If you make pour-over coffee using the kettle, every 2.4 extra teaspoons of water heated to boiling results in 1g of CO₂ released into the atmosphere. If we get a coffee pot with a burner to keep the coffee warm, that would likely be the most significant energy loss in the whole system. If we get an airpot brewing system or even a traditional Mr. Coffee, then every cup of coffee left over at the end of the day or thrown away because it is cold or stale is two K-Cups worth of CO₂ emissions wasted.

That also doesn’t count the roasted coffee used. Every other method calls for using more coffee than the K-Cup contains. Instructions for Century Series Air Pot Brewers call for 2.5oz of roasted coffee to produce 2.2L of coffee, which comes out to 11.43g per 12oz cup. If we produced coffee in accordance with the instructions, and drank every single cup, that is more efficient than a Disposable K-Cup. But between the coffee and the power, every wasted 12oz cup has a carbon footprint of 72.4 g CO₂ (43g from coffee, 29.4g from heating water), or the equivalent to the plastic in 4.2 disposable K-Cups (that is also under ideal conditions; the calculation for heating water above doesn’t account for any losses). 11.43g of roasted coffee is also on the low end, as this source recommends 21.26g of roasted coffee per 12oz cup, which appears to align with a common suggestion of 20g per 12oz cup for other methods. One of the biggest efficiencies from K-Cups is that they result in no wasted cups of coffee at the end of the day; people don’t have to brew a whole pot of coffee to drink just one cup.

Conclusion: Coffee is energy-intensive no matter how you choose to go about making it. But because the Disposable K-Cup is such a resource-efficient method of brewing coffee, it is the least bad method. By eliminating Disposable K-Cups, we’ve eliminated that plastic from landfills but traded it for a larger mass of CO₂ released into the atmosphere, where it is a much tougher problem to deal with. Plastic is unsightly but once you dump it in a landfill it tends to actually stay there. It is easier to pretend that the CO₂ isn’t a problem, but that’s only because we can’t see it.

Appendix 1: Creamers

Dairy milk produces 1467g of CO₂ per liter of milk. Almond milk produces 396g of CO₂ per liter. A standard creamer packet contains 11mL of liquid. If you assume people put 22mL (two creamer packets) of milk into their coffee (for those that do), that is 32.3g of CO₂ per cup of coffee for dairy milk and 8.7g of CO₂ per cup of coffee for almond milk. Each creamer packet worth of dairy milk is just shy of 1 disposable K-Cup worth of plastic in terms of CO₂ emissions.