Caffeine fix: how much caffeine is in used coffee grounds?

Want to know how much caffeine in used coffee grounds? Let’s find out…

What the heck is caffeine?

The thing that gets you out of bed? Your post-workout pick-me-up?

Caffeine is key (like KEY, key). But what actually is it? What would you get if you said, ‘hey, coffee roaster, give me some caffeine’?

A white powdery substance, that’s what. Unlike most of the other compounds in coffee, caffeine can be extracted to form a solid chemical. Caffeine is a water-soluble alkaloid occurring naturally in over 60 plant species. Plants use caffeine to repel pests, while we mainly consume it in the forms of tea, coffee, chocolate and energy drinks to boost our brain function. Caffeine is popular worldwide – it takes the top spot as the world’s most widely consumed psychoactive substance.

There’s absolutely nothing wrong with consuming caffeine in moderate amounts. It’s even been found to help diabetics and heart disease sufferers, and can enhance memory. Now that’s something to remember…

How much caffeine is in coffee beans?

This is a tricky one to answer because lots of little factors play their part. Let’s keep things simple and start with a single arabica coffee bean (aww…). On average, this little fella contains 1.9 milligrams of caffeine. Robusta coffee (the bitter stuff) contains quite a bit more; one robusta bean has approximately 2.9 milligrams of caffeine.

We rarely deal in individual coffee beans, so the next question is this: how much caffeine is there in one gram of coffee? Arabica coffee has a caffeine content of 12 milligrams per gram of coffee. For robusta, it’s about 27 milligrams.

We only roast quality arabica beans at Two Chimps, but before you put a grumpy face on and think we’re being stingy on the caffeine, give us a moment to explain why robusta contain so much caffeine.

• High altitudes give better quality coffee
• Delicious arabica coffee plants mainly grow at high altitudes
• There are fewer pests high up. Coffee plants use caffeine as a natural repellent, so high altitude arabica coffee plants need less caffeine.
• Robusta beans grow at lower altitudes, where there are more pests. They’ve been forced to adapted to contain more insect-repelling caffeine.
• This is the reasons why robusta coffee tastes so bitter – it’s got a helluva lot of caffeine to keep those bugs at bay!

Coffee brewing method caffeine content

Let’s check out those little factors we mentioned before – all the other bits and bobs that affect how much caffeine your coffee contains.

The brew method you use can alter the amount of caffeine in your cup. It’s largely down to the length of each brew time. Caffeine is water-soluble (it dissolves in water), which means that brew methods with longer brew times give a cup buzzing with caffeine. Why? Because there is more time for the ground coffee to extract into the water.

The average mug of filter coffee contains 140mg of caffeine.

• A 30ml sample of espresso, for instance, gives you about 126mg of caffeine
• Cold brew is the second strongest – a 30ml sample contains 67mg of caffeine
• Moka pot coffee has around 66mg of caffeine per 30ml
• A 30ml sip of cafetiere coffee will give you a 22mg caffeine fix
• Filter coffee has the lowest caffeine content. 30ml gives you about 21mg

And milky coffees? Your latte or cappuccino contains the same amount of caffeine as the single or double shot the barista used, as milk contains zilch caffeine.

How much caffeine is in used coffee grounds?

Used coffee grounds contain less caffeine than unbrewed grounds or whole beans because some of the caffeine dissolves into the water during the extraction.

Compounds (flavour, aroma etc.) all extract at different rates, with caffeine being one of the last to wiggle its way out. Remember what we said about brew times being important? Longer brew times give more time for more caffeine to extract. This is why coffee can taste bitter if longer slips into too long –  your lovely coffee has over-extracted.

But let’s get back to those used grounds. How much caffeine do you contain, oh lumpy brown sludge? Specific is impossible, but we can give you a ballpark figure. On average, used coffee grounds contain between 3.59 and 8.09 milligrams of caffeine per gram. Flick back to the top of this article, and you’ll see that this is quite a bit less than the 12 milligrams of caffeine per gram of fresh ground coffee. Where has it all gone? Into that lucky first mug!

It’s hard to be exact when answering the how much coffee in used grounds question. This is because different coffees (espresso, filter etc.) contain different amounts of caffeine, which means that the grounds left behind all contain varying measures, too.

Can I use coffee grounds more than once?

We’re cheerleaders of the waste not, want not approach, but not when it comes to used ground coffee.

Coffee made with second-hand grounds will taste flat and flavourless. Scroll back up again, but to the bit about rates of extraction this time. Flavour and aroma compounds extract first and are largely used up in that awesome first brew. So the one made with used grounds will taste a bit, well, drab.

Coffee made with used grounds might also taste overly bitter. You use most of the flavour compounds in the first brew but caffeine, which takes longer to extract, is still in the grounds. Brew with used grounds, and these caffeine molecules are mainly what you’ll get!  Great news if you want a cup that’s all caffeine and no flavour but, as you’re reading this, I’m guessing you’re not part of that pack. You’re part of #teamtaste, and we’re not keen on reusing coffee grounds unless we really need to!

Don’t put used grounds back in your mug – put them on the garden instead!

Want to know how to make your regular coffee super healthy? Just click below! 💪

Top tips this way!