Marike Stucke

June 16, 2025, 4:14 am | Read time: 5 minutes

Germans are true coffee enthusiasts: According to a study by Techniker Krankenkasse, coffee ranks second among favorite beverages, right after water. Whether in capsules, pods, or as loose coffee in a drip coffee maker or automatic machine, coffee grounds are always left over. Most people carelessly throw them away, but coffee grounds can enrich compost in your garden with valuable nutrients (and can also be disposed of in the organic waste bin for the same purpose without a capsule). But what should you consider when disposing of them on the compost heap? And how do coffee grounds affect compost quality?

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Why are coffee grounds suitable for compost?

Coffee grounds contain numerous nutrients beneficial to plants: In addition to nitrogen, potassium, phosphorus, and other trace elements, they provide organic material for microorganisms in the compost. This contributes to humus formation and promotes soil life.

Another advantage: Coffee grounds attract earthworms, which improve composting through their constant movement and mixing of materials. Coffee grounds are also good moisture retainers and can positively influence the moisture level in the compost.

How coffee grounds directly affect compost

• Nitrogen source: Coffee grounds contain a relatively high amount of nitrogen, which is important for plant growth and stimulates the decomposition process in compost. About two percent nitrogen is present in coffee grounds.
• Promotes soil life: Earthworms and microorganisms love coffee grounds and feed on them and their decomposition products. Thus, coffee grounds indirectly ensure faster and more even decomposition.
• pH value: Despite its slightly acidic origin (pH around 6.5), coffee grounds have little significant impact on the pH value in well-balanced compost, especially in a well-mixed pile.

What should you consider when composting coffee grounds?

Despite the many benefits of coffee grounds for compost, there are some points that hobby gardeners should consider:

• Always distribute coffee grounds well: They should not be placed in thick layers on the compost, as this can promote mold or rot. Better: Spread the moist grounds thinly and evenly over the entire compost. Ideally, they should be regularly mixed with other materials (such as leaves, grass clippings, straw).
• Only unbleached paper filters are safe: Those who use filter coffee can add the filter bag along with the coffee grounds to the compost–modern filters made of unbleached paper decompose well. Bleached filter bags or coffee capsules, of course, do not belong on the compost.
• Consider the amount: While coffee grounds are nutrient-rich, they should only make up a small portion of the total compost material. A rule of thumb: No more than 10 to 15 percent of the compost volume. Otherwise, the pH value of the compost could drop too much, resulting in a more acidic level. Many microorganisms do not thrive in this environment, and only a few garden plants, such as hibiscus, hydrangeas, or berry bushes, prefer acidic compost.

Which plants benefit from enriched compost?

As long as not too many coffee grounds end up in the compost, all garden plants tolerate the nutrient-rich humus well. Those who dispose of a lot of coffee grounds should only use the resulting compost for a group of acid-loving plants. These include, for example:

• Berry bushes (e.g., raspberries, blueberries)
• Tomatoes
• Roses
• Ornamental shrubs
• Hydrangeas

Sensitive plants that prefer calcareous soils or are pH-sensitive should be supplied with it more sparingly.

More on the topic

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Can coffee grounds be used directly as fertilizer?

Coffee grounds can also be used directly as a mild fertilizer in the garden for acid-loving plants. Simply sprinkle cooled coffee grounds sparingly around plants and lightly work them in. However, they do not replace a complete fertilization, as they contain only a small concentration of the necessary nutrients. They do, however, cause a slight acidification of the soil and can improve the environment for plants that prefer a slightly acidic pH in more calcareous soils.

Another positive side effect: Coffee grounds can act as a natural barrier against slugs–the caffeine they contain acts as a neurotoxin to these soft-bodied creatures, and they avoid areas sprinkled with coffee grounds. Around the lettuce bed, for example, is also a good place to spread coffee grounds.

Conclusion

Coffee grounds are far too valuable for the trash. Those who use them wisely on the compost promote decomposition, enrich the humus, and support soil life. The key is the right dosage and good mixing with other materials. This way, you can enjoy your morning coffee twice–as an energy boost for the hobby gardener and as a nutrient source for the garden.