This edited extract is from the breakfast chapter of Sarah Bridle’s Food and Climate Change Without the Hot Air.
Tea and Coffee
As you drop the teabag into your cup, think about its journey from tea plants far away. The good news is that transporting a teaspoon (2 grams) of tea half way across the world by boat causes very little greenhouse-gas emissions compared to most other things you’re likely to eat today.
What about boiling the water? Burning natural gas to heat a pan, or using electricity generated from burning coal or natural gas, unlocks carbon dioxide taken up by plants millions of years ago, and releases it back into the atmosphere, which causes global warming.
30 gCO2e of greenhouse-gas emissions are caused by making one cup of black tea assuming that, like many people, you boil twice as much water as you really need.
Boiling the water causes more emissions than the teabag itself, but even so the total is still small compared to our reference value of 3 kg per day per person.
1 g teabag = 3 g emissions
Do you prefer coffee? Coffee is made from the seeds of the coffea plant, which are often referred to as “beans”. To grow well, the coffea plants are tended, watered and fertilized. For dried coffee, the emissions from the fertilizer cause about one third of the total emissions; processing the bean from plant to cup and packaging contribute most of the remainder.
1 g instant coffee powder = 17 g emissions
For a typical cup of coffee, the instant coffee emissions are similar to those from boiling the water. Even so, the amount of emissions from a single cup, are small compared to our reference value of 3 kg per day per person.
Coffee shops have conveniently sprung up on street corners all over the world, helping us get a quick fix of caffeine on the go. Many of these drinks are taken away in disposable cups. This generates waste that often goes to landfill, but how bad is the cardboard for climate change?
If the cardboard is composted with good access to oxygen, it decomposes back into carbon dioxide, thus returns to the air the greenhouse gases absorbed by the tree. In this case the emissions are just those from generating the energy to process the wood into cardboard, which is roughly equal to the weight of the cardboard.
1 g cardboard, composted = 1 g emissions
However, if the cardboard is sent to landfill, it is likely to rot into methane, so the total emissions are larger, rising to twice the weight of the cardboard.
1 g cardboard, landfilled = 2 g emissions
Most people in the UK drink their tea with milk, typically adding just over one tablespoon (20 ml) to each cup.
Are you concerned about all the plastic milk cartons? In fact, when it comes to greenhouse-gas emissions, the plastic isn’t a big deal compared to the milk itself. Even if we bought all our milk in small plastic bottles, the emissions from producing the plastic would be dwarfed by emissions from the cows themselves.
How do cows contribute to climate change? Tabloid newspaper headlines warn about methane from cow farts, but in fact most methane comes out of their mouths as burps.
Exactly how much methane are we talking about? A typical dairy cow eats over 70,000 kCal a day – about the same intake as 30 humans. To be fair, the cow is churning out milk at an average rate of 16 litres a day, but at the same time it’s burping out over 7 kilos of emissions each day.
We can already estimate the emissions from milk by sharing out the 7 kilos of emissions across the 16 litres of milk produced. A more accurate calculation takes into account the methane burped by the cow during the two years before it reached milk-bearing age. Since cows are then slaughtered for beef at around the age of 4, then this roughly doubles the milk emissions, although the emissions can then be shared out between the milk and the beef.
In addition to the cow burps, we have to add in the impact from cow poo. Depending on how it’s stored and distributed on the fields as fertilizer, cow manure produces both methane and nitrous oxide and adds about 50% to the total milk emissions.
1 g milk = 2 g emissions
Overall, cows’ milk causes about twice its own weight in greenhouse-gas emissions, but this number can vary by more than 50% depending on how the cows are raised. For example, if the cows produce less milk each day then the emissions will be higher.
Milk in tea and coffee
We can now add up the total emissions caused by a cup of tea with milk: we find that half of the emissions come from the milk. For white coffee, the emissions from a splash of milk (20 ml) are slightly more than those from a teaspoon of coffee granules.
However, if you’re drinking ten cups a day, and being a bit generous with the milk or leaving a lot of water in the kettle, you might want to think more carefully. (Ten cups of white tea causes over 25% of the reference 3 kg daily food emissions.) However, you can bring the emissions from your drink of choice to relatively insignificant levels by only boiling the water you need.
How about a latte or a cappuccino? Popular coffee shops serve half-litre cups of latte, made from a shot of espresso topped up with milk. The emissions from making a latte are more than ten times those from a regular cup of coffee, almost entirely because of the large amount of milk.
How can you reduce emissions?
How could milk emissions be reduced? Plant-based milk alternatives have become popular. Overall the emissions from producing plant-based milks are usually found to be less than half of those from dairy milk.
1 g plant milk = 0.8 g emissions
Keen to learn more? Food and Climate Change Without the Hot Air covers popular breakfast, lunch, snack and dinner options.