资源环境科技发展态势分析平台

If you are like me, you can’t imagine starting your day without a couple of cups of strong coffee. It jump-starts the mind. Coffee consumption is growing faster than the human population, with annual consumption now topping 10 million tons per year. But just as I have considered for milk and booze, coffee has a bunch of environmental impacts that begin with how it is grown and extend to how we dispose of it in the environment.

The impacts of coffee production on tropical forests have been discussed for decades. Most tropical ecologists believe that the growth and harvest of coffee in the shade—that is, under an intact canopy of tropical forest—is not too bad for the environment. However, when the price of coffee rises, so does that rate of deforestation to provide for sun-grown coffee in the tropics. Sun-grown coffee results in the loss of birds common in mature tropical forests. But, the story is not unequivocal: some species of birds actually do better or even colonize sun-coffee plantations. For a regional landscape, the greatest number of birds will be found in a mosaic of forest and coffee plantations, especially if the tracts of forest are large.

In terms of energy use, more than half of the environmental impact in the production of coffee occurs in the plantations where coffee is grown, to account for cultivation, fertilizers and pesticides. When you decide to have a cup of coffee, you have already made your largest contribution to the energy used to deliver coffee to your cup.

How we brew coffee determines most of the rest of the energy use. Should we use French press, a traditional drip-pot, or one of the new modular or “pod” brewing systems. There is no contest in terms of resources used to manufacture the system—pod-brewing systems use much more material, especially in plastics and electronics—all of which take energy to produce.

How coffee pots are employed flips the evaluation. Considerable energy is used when consumers brew a full pot using traditional methods, but then leave the heat on to keep it warm for the rest of the morning. Pod-brewing systems that are maintained on phantom power between brews use less energy per cup. Unfortunately, pod-brewing systems that are left in standby mode—where hot water is kept available for the next user—have the worst environmental impact, dwarfing the difference in impact between traditional drip and pod-brewing systems. Overall, French press systems use the least energy at every stage.

The pods themselves create environmental impact, both in their manufacture and in disposal. Some pods are now advertised to be recyclable, but the limited data available suggest that this is infrequent. Most used pods end up in a landfill. The production and disposal of coffee pods accounts for up to 1/3 of the energy used to brew coffee in those machines.

Caffeine is now found as a ubiquitous contaminant in natural waters, especially in countries with high and increasing coffee consumption. Some caffeine is derived from the disposal of waste coffee and coffee grounds, whereas some, typically 2 to 3%, passes through the human system intact and contaminates sewage waters. Sewage treatment can remove up to 70 to 98 % of caffeine, so if sewage waters are treated only a small amount of caffeine passes into natural waters, where it exposes fish and other wildlife. Nevertheless, one recent study found that 35% of environmental samples worldwide had caffeine concentrations that were above the threshold of undesirable effects on organisms (4 to 15 ug/L).

If you must have coffee, buy shade-grown coffee, brew it by French press, and reduce your impact on nature by disposing of the coffee grounds in compost.

References

Brommer, E., B. Stratmann, and D. Quack. 2011. Environmental impacts of different methods of coffee preparation. International Journal of Consumer Studies 35: 212-220.

Hicks, A. and H. Halvorsen. 2019. Environmental impact of evolving coffee technologies. International Journal of Life Cycle Assessment 24: 1396-1408.

O’Brien, T.G. and M.F. Kinnaird. 2003. Caffeine and conservation. Science 300: 587.

Quadra, G.R. and 7 others. 2020. A global trend of caffeine consumption over time and related-environmental impacts. Environmental Pollution 256: doi: 10.1016/j.envpol.2019.113343.

Rodríguez-Gil, J., and 3 others. 2018. Caffeine and paraxanthine in aquatic systems: global exposure distributions and probabilistic risk assessment. Science of the Total Environment 612, 1058e1071.

Schlesinger, W.H. 2019. How green is your milk?

Schlesinger, W.H. 2016. How green is your booze?

Sekercioglu, C.H. and 5 others. 2019. Long-term declines in bird populations in tropical agricultural countryside. Proceedings of the National Academy of Sciences 116: 9903-9912.