Every year, New Zealand produces thousands of tonnes of ground coffee waste. The vast majority of this goes directly to landfill where it contributes to climate change through the production of methane - a greenhouse gas which is 34 times more potent than carbon dioxide. Fortunately, we all have part to play to reduce this waste. By using ground coffee in our gardens, we can divert this waste from entering landfill and simultaneously provide a sustainable source of nutrients to our plants. Natural Habitats is already using coffee grounds in our Ultralite Greenwall media - it keeps certain pests off our plants!
So how can used coffee grounds be utilised in your garden?
Adding used coffee grounds to your compost
Adding used coffee grounds to your compost bin will decompose any toxic components remaining in your coffee. It will then produce a natural fertiliser that can improve soil water holding capacity and promote plant growth, particularly in green veggies. The trick however is not to add too much: the ideal amount of coffee to add to your compost bin is around 20%, as this will promote a range of organisms to grow without causing nitrogen drawdown or phytotoxicity.
Want to get composting but unsure how to start? We’ve got you covered in this article
Adding used coffee grounds to your soil
Used coffee can be incorporated directly into the soil structure. Coffee grounds contain a decent amount of nutrients such as nitrogen as well as phosphorus, potassium, zinc and iron. Adding coffee to your soil therefore improves the availability of these micronutrients in the soil. To maximise these fertilisation benefits, simply sprinkle a thin layer of used coffee onto your soil.
Adding used coffee grounds to your mulch
Used coffee can be applied to surface soil as a mulch. As a mulch, ground coffee will assist with soil temperature control and help to control weeds and pests. Being too liberal with coffee grounds can have an adverse effect however; too much caffeine is thought to suppress germination and growth, so we recommend that you avoid spreading it on seeds. Also, because coffee grounds are so fine they can clump together, similar to a clay-based soil. This can make it tough for water to penetrate your soil. The solution is to use mix coffee grounds with other organic matter, such as compost, before using it as a mulch. Alternatively, rake your coffee grounds into the top layer of soil so that they can’t clump together. Remember – the key to good soil structure is variable particle size.
Adding Coffee to your Worm Farm
Got a worm farm at home? Then you’ve got a ready-made crowd who will love your used coffee. Worms break down used coffee and turn it into a natural soil conditioner. By tossing your coffee grounds in along with other food scraps, it decomposes and produces worm castings (an organic form of fertiliser produced by earthworms) which can aid in germination and act as a liquid fertiliser when diluted with water.
Are you ready to give your garden a caffeinated kick-start? You can use the grounds from your own coffee machine or plunger, or why not take a container to your local café and ask to lighten their load?