Since we began the Green Coffee Shop Scheme four months ago, we have saved over 12 tonnes of coffee grounds from going to landfill, from the first week at the beginning of June when we collected 200kg, to last week’s collection of almost 900kg. Working with cafes, coffee shops, restaurants and offices across Cambridge and South Cambridgeshire we’re having a significant impact in terms of reducing the waste we produce and capturing a valuable resource.

So what *is* the value in a cup of spent coffee grounds?

As I described in a previous blog post, so far our coffee grounds have been going to biobean. Based near Alconbury, they transform coffee grounds into ‘Coffee Logs’, a solid fuel that can be used in the place of wood. They burn 20% hotter and longer than wood logs and are, of course, using a resource that would otherwise be lost.

However, our coffee grounds are now also bringing benefit to a local business in another way too. We are now providing some of our coffee grounds to Waterland Organics, near Lode. Waterland Organics is a small family business run by Paul and Doreen on their farm, Willow Farm. They provide organic fruit and vegetables to retailers and households across Cambridge.

As an organic farm, they use no artificial fertilisers. Five years ago, Paul made the decision to stop using animal inputs to enhance the farm’s fertility. This left them with just plant-based inputs – and they knew that maintaining the soil’s potassium levels would be a major challenge.

Potassium is an essential plant nutrient. It is needed for proper growth and reproduction and plays a number of different roles in the functioning of plants, including the regulation of CO2 uptake (by regulating the opening and closing of stomata); regulation of water, both uptake through the roots and loss through stomata; the synthesis of proteins and starches; and is essential for the production of Adenosine Triphosphate, the energy source for many chemical processes that take place in plant tissues.

Potassium is most readily available in clay soils. However, due to its location in the Fens, the soils at Willow Farm are dominated by sand and gravel. The use of green manures on the farm has enabled nutrients such as phosphate and magnesium to be drawn up from the deeper clays, but over the years potassium levels at Willow Farm have continued to fall.

This is where our cup of coffee comes in.

Coffee grounds are naturally high in potassium. They’re often used by gardenerers as an addition to composts and act as a slow-release fertiliser. With the coffee grounds from hundreds of cups of coffee drunk across Cambridgeshire, Waterland Organics will see crop yields improve. The solution is sustainable and has very low carbon emissions associated with it, as we’re using a material that would otherwise have gone to landfill. Our first delivery of coffee grounds was even made in a zero-emission electric vehicle.

It gets even better. We’re all about efficiency and making the best use of our vans being out on the road. At the same time as we drop off the coffee grounds for composting, we collect fabulous organic veg for the Cambridge Organic Food Company, which goes out to households and wholesale customers.

Reducing waste, bringing benefit to a small local farm, and developing circular food supply chains – what’s not to love?