Relax your plants with a coffee...
I adore a good cup of coffee, whether it’s hot or iced I’m there, I love visiting my local coffee shop to see what flavour/invention/blend is on the menu board, trying something new, something different is the highlight of my week. And my spirits was lifted more when I found out coffee can help weight loss….well I was sold completely after that!
As a nation and indeed as a planet we enjoy coffee, with coffee being the number two world commodity after crude oil! 90% of all the coffee production occurs in developing countries whereas the majority of coffee consumption occurs in developed countries and is focuses within cities & towns. How many places within Derry, Coleraine, Limavady, Strabane etc can you get a cup of coffee? (I bet there’s more coffee houses than bars!)
One of the downsides of all this coffee drinking is the spent coffee grounds left behind after brewing, some 6 million tonnes worldwide is produced, locally you can get around 40-100kg per week from a café. And like most food wastes, this coffee residue have high volume but low value, so its mostly disposed of in landfill.
However spent coffee granules are increasingly being used by gardeners, usually by disposal of small amounts directly into the soil, or by mixing in composting piles. Small amounts added to the soil may be toxic to soil microorganisms (due to their Phenol content) but at the same time these toxins provide a natural pesticide and herbicide. However composted coffee grounds have been shown to positively increase the growth of certain horticultural plants.
Spent coffee grounds
In field trials where spent coffee grounds have been used in Horticulture, after harvesting there was significant weed growth suppression, with a 20% volume of spent coffee grounds in soil supressing weed growth to such an extent it was almost prevented.
In field trials if you add any significant amount of fresh spent coffee grounds to soil it significantly decreased plant growth, you have to keep the volume less than 1kg/m2 to not affect plant growth. Whereas composted spent coffee grounds have been shown to improve the nutritional content of vegetables, with the Potassium content in lettuces being increased by 40% when 5% of composted spent coffee grounds are included in the potting mix, this may be valuable as with the increased consumption of processed food, with lower Potassium amounts, combined with a reduction in the ingestion of fruits and vegetables, this has led to a decline in Potassium intake by people, Blood Pressure decreases can be observed by increasing Potassium intake, aswell as cardiovascular disease mortality reduction.
Spent coffee grounds best added to compost pile
So from now on, make a point in visiting your local coffee house, ask them to keep you the spent coffee granules and start adding it to your compost bin. When you start to gather it you may have a bit of mould in the coffee you gather, this is normal (there is substantial sugars in this waste), just add this away to your compost bin!
Connect with Gareth
Gareth Austin is a broadcaster and lecturer in Horticulture. Join Gareth on Twitter @GardenerGareth or connect via Facebook to enjoy his regular adventures in the world of Horticulture.
