Did you ever wonder how many tonnes of nutrient-rich coffee waste are produced in a city each day? Shane Genziuk, of Bentleigh East, Victoria, did the sums. Staggered by the answer, Shane collected a team of volunteers and began harvesting some of the waste.

Used coffee grounds have been a compost additive and nitrogen-based fertiliser for centuries, and this tradition continues today with a growing number of gardeners from around the world.

There is in fact a staggering amount of the stuff out there needing to be collected.

Of the seven million metric tonnes of coffee consumed worldwide in 2009, only a tiny fraction of the resulting byproduct (coffee grounds) were used effectively. In Australia over the same period, we each consumed on average three kilograms of coffee (or about 62 tonnes). Almost all of this ends up in landfill, and that leads directly to the creation of methane gas, a nasty greenhouse gas (and not too pleasant smelling either!).

Coffee drinkers are responsible for this situation, because around twenty grams of coffee grounds are left over from every espresso drink, whether straight shot, cappuccino or latte. Twenty grams might not sound like a lot, but it only takes 50,000 lattes to make one tonne, which any large city would do many times over each day.

So what we have is a huge amount of used coffee grounds going to waste, and an ancient practice that turns this same waste into a cost-effective soil and compost additive.

Why coffee grounds for your garden?

• Earthworms love used coffee grounds, and will increase in numbers as you continue to add them to the soil.

  Coffee grounds are a good source of nitrogen, with a carbon to nitrogen ratio of 20–24:1, which is about the same as grass clippings. This makes coffee grounds a green addition to the compost bin. For each 20 to 24 parts of carbon, there is one part of nitrogen. Cardboard is 350 to 1, newspaper about 150 to 1, vegie scraps from 20 to 25 to 1. On the whole, the carbon/nitrogen balance for coffee grounds is ideal for making compost. Modern commercial fertilisers make that ratio look low, but in nature it is just fine.
• Coffee grounds contain small amounts of phosphorus and potassium (a typical NPK analysis would show a ratio of 2.1 : 0.3 : 0.3), and includes magnesium (a secondary nutrient) and copper (a micronutrient), in such quantities that you will not need to supplement them from other sources.
• Earthworms love used coffee grounds, and will increase in numbers as you continue to add them to the soil. You will also notice an increased population in the worm farm when grounds are added.
• Used grounds are good for retaining moisture and assist in loosening soil.
• From experience, coffee grounds deter snails, slugs and ants, and there are some who believe they deter cats from the garden.
• Used grounds can be applied directly onto the lawn, or in liquid form to pour into the soil. • pH level— there is a general belief that used coffee grounds are highly acidic. However, much of the beans' acid content is fl ushed out during the brewing process. Most of the freshly used coffee grounds I have tested sit within a pH range of 6.2 to 6.9, with some as low as 5 to 5.5. This means they can be applied directly to most soils without fear of killing your plants, and even better, if added into compost first, the pH levels of coffee grounds will normalise over time. The same is true of coffee grounds added to the worm farm — what comes out is more or less neutral.

Getting involved

This is the easiest part, because the finished product is waiting for you at the office or local cafe right now! Any espresso machine is a source of used coffee grounds, and all you need to do is get them home and into the soil or compost. A handful within the root zone of most plants every week is plenty, and a bucket-load into the compost will help create a beautifully dark and rich finished product.

Last year, I started the group Ground to Ground, which relies on volunteers to collect used coffee grounds from offices and cafes. Starting it off was a big step for me, because for years I had been promising myself to get involved with the community. After collecting close to two tonnes of coffee grounds for my own use, the connection hit me. If I could do this in my own back yard, then surely there would be others out there like me — and what a difference that could make for the community. So the problem of always waiting to take a lead in something solved itself!

There has been no shortage of volunteers for Ground to Ground, at home and abroad. I've been amazed by the diverse groups and individuals that have found me via the website or in general conversations and asked for more information. There are plenty of gardeners out there who already know about the benefits of used coffee grounds, and it can be difficult for individuals to start out, to work with the cafe manager or at their own office to set up a process. What we are doing is making the whole thing easier for everyone, and recording our successes to encourage others to join in.

There have been some challenges along the way, mostly when it comes to asking cafe managers to start making their used coffee grounds available for collection. For some cafes, taking the extra five minutes a day to keep the grounds clean and in a separate bin seems like too much hard work, and this behaviour can be difficult to change.

However, for every cafe that does not want to get involved there will be a couple that do, and those successes are an incentive to keep going.

The biggest success to date has been our increasing levels of self-sufficiency. As more and more of this quality organic material is added into the soil you can actually see improvements over time, which results in higher yields over a longer period, and the ability to support an increased variety of vegetation. Healthy soil encourages diversity in animal and insect life, with everything playing its part as intended.

The ultimate success of Ground to Ground is to encourage a future where it is considered as normal to reuse coffee grounds as it is to throw plastics and paper into the recycling bin. That is the vision I am working towards. So to get involved, have a chat to your local cafe about what they do with their used coffee grounds, and you will normally find them more than happy to leave some aside for you. It takes just five people to collect all the coffee grounds that a typical cafe produces, and over time this represents a real reduction in their contribution to landfill and sends a very positive message to their customers. I have collected tonnes of used coffee grounds for my garden, and in doing so have transformed the quality of my soil and plants. It feels great to know the difference I am making to our environment, and hope you can find a place in your gardening routine to join me.

To find us online, just search 'Ground to Ground' or go to groundtoground.org. You are welcome to all the resources on the site, and I am always available to help out. Best of luck!

Photos by Fiona Tunnicliff

References

International Coffee Organisation: www.ico.org/prices/po.htm
Coffee consumption statistics: http://chartsbin.com/view/581
Coffee statistics: http://factsanddetails.com/world. php?itemid=1567&catid=54&subcatid=346