Spent Coffee Grounds - A Guide to their Uses

Expectation vs. reality making coffee lampshades

Over 1.5 million tonnes of coffee grounds are sent to landfill around the world every year. In the UK and Ireland alone it’s over 600,000 tonnes or up to 93% of all the coffee waste produced. 

A huge amount and an indication of just how popular this new drug of choice has become. 

Coffee shops are replacing the pub for people to hang out in and it’s socially acceptable to have all night coffee houses and even drive by coffee collection points.  

These facts passed me by and as I don’t drink coffee.

This changed last week when I was looking online for new lampshades to make ( I tend to make these when winter comes to keep my sanity until I can get out in the garden again). 

I’ve made shades out of various materials, concrete, paper, old car parts, plumbing material, plastic, old spanners and even dog hair, so when I saw a shade made from spent coffee grounds I thought “ I could do that”

 I’m being proved wrong. 

The images of these super smooth, tough and durable shades were  the result of 5 years’ worth of tinkering with materials and a special ‘patented secret formula’ so the designer said on their website. How hard can it be? Just a few dollops of PVA soaked grounds put into a cone shape and were away. Wait a week and then hang up the resulting shade. 

It’s a case of expectation versus reality here. I have not a collection of cup and plate shaped shades (I use the term lightly) that bear no resemblance to the original images. I was also told in the blurb on the website that the shades “emit a delightful smell of freshly ground coffee when the bulb heats the shade” erm, no they don’t. I’ve been sneezing every time I walk past them and the rest of the family thing that there’s a pile of old grounds in the kitchen compost bin rotting away and keep asking what the horrible pong is.  The compost bin is probably where they belong… but is it?

There are a lot of potential uses for spent grounds and the more ways to recycle the waste, the less the large coffee chains have to pay for getting rid of their by product. 

Some uses found so far are:

•  Add to the compost 
• Used to dye paper and cloth.
• Mix with glue and touch up furniture.
• Flea repellent.
• Odour eliminator.
• Soak up grease.
• Covert to laundry detergent.
• Make into bioplastic.
• Use as a biofuel. Oil is extracted from the waste, grounds are dried to filter impurities in biofuel production, and any remnants are burnt as a source of energy from electricity.
• Firelogs.

It’s the composting of the grounds that I am concentrating on now as I haven’t the patience to “tinker” for 5 years to get the mix right for lampshades.

I have decided to do a test bed with the coffee I collected from the shops last week. I got over 5kg from about 10 shops who all happily dropped their used grounds into my open bin bag. There are some large companies who have bags of grounds on the counter for us gardeners to collect but I didn’t come across any. One shop chain spokesperson said they have now stopped giving away the grounds all together to the public after an email was sent to all of the outlets, I’m not sure why, probably people were trying to boil up an extra brew in their kitchens.

I’m not very hopeful the grounds will improve my garden.  Tests have been done before and the results have not been particularly successful, only in one case of growing oyster mushrooms did the grower actually say there was an improvement in their crop. It could be a case of old wives tales and hearing of the benefits often enough in press releases from the coffee shops could actually make us believe the hype. In most cases large amounts of grounds added to the garden slows plant growth and actually kills plants. 

Coffee grounds are a rich source of caffeine, richer than coffee itself, depending on the brewing technique. One of the key functions of caffeine in the plants that produce it is ‘allelopathy’ ,the ability to reduce competition from surrounding species by suppressing their growth. Caffeine is packed into coffee seeds for the very function of suppressing the germination of other seeds.

Studies suggest it also stalls root growth in young plants, preventing their uptake of water and nutrients. Yet others have shown it has antibacterial effects (so much for boosting soil bacteria). It’s not really acidic either so throwing it around your rhododendrons won’t really do much.

I’ll probably start by just adding the coffee to the compost bin and let the worms work on it,. Even this gets mixed reviews. Some vermicomposters (worm growers) say the spent ground don’t hold water so are not very palatable. I’ll mix mine in with other wetter food scraps as big clumps of coffee might heat up too much.  

Just in case you were wondering if dry coffee grounds deter slugs and snails – They don’t!  I’ve had the bag outside and it’s full of them. 

The ‘Old Wives’ have been at it again.