The Zero Waste Coffee Project

How to make great use of coffee grounds

This article was first published on February 13, 2022 (The Conversation)

Courtesy to María Dolores del Castillo Bilbao*, Amaia Iriondo de Hond**

To start the day with energy, more than 22 million people in Spain (63% of Spaniards over the age of 15) drink at least one cup of coffee a day. Of these, 32% in a coffee shop and the remaining 68% at home. But what happens to the tons of coffee grounds that are generated when preparing this delicious and healthy drink?

Probably the first thing that comes to mind is to use it to fertilize plants or unblock pipes. But you can go much further. To make the most of coffee grounds, the best thing to do is to eat them! But not just any old way.

The following recipe for biscuits made from coffee grounds is the result of research aimed at evaluating their use as a food ingredient and their application in baked goods.

The results showed that they are a natural source of antioxidant insoluble fibre, essential amino acids and low glycaemic index sugars. What's more, the biscuits are of high nutritional quality, are very tasty, have the potential to reduce the risk of chronic diseases such as obesity and diabetes, and help people fall asleep.

This is the recipe for coffee grounds biscuits, a healthy and sustainable snack:

Biscuits made from coffee grounds.
Ingredients:

- 60 g wheat flour
- 20 g water
- 8 g sunflower oil
- 0.6 g yeast
- 0.4 g salt
- 0.35 g soy lecithin
- 2 g stevia
- 3,5 g fructo-oligosaccharides (FOS also known as Beneo or inulin)
- 4.5 g coffee grounds*.

Preparation:

* Preheat the oven to 185°C and line a baking tray with baking paper.
* Mix all the ingredients in a bowl until you have a dough.

* Roll out the dough with a rolling pin, cut out the biscuits with a mould or a glass and place the biscuits on the previously prepared tray.
* Bake the biscuits for about 15 minutes (185 °C), remove them from the oven and let them cool.

Cookie made with spent coffee grounds

How to use coffee grounds
You can use fresh coffee grounds, those obtained from a freshly brewed beverage by any method (drip, French press, Italian coffee machine, etc.). Coffee grounds from capsules can also be used. If they are not used within a few hours after the preparation of the beverage, they can be dried in an oven at over 185°C until all water is removed and stored in a cool, dry place until use. Dregs from the industrial processing of instant or soluble coffee can also be used for this purpose.

Alternatively, the wet grounds can be kept frozen (-20°C) until sufficient quantities are available to make a number of healthy biscuits rich in fibre and low in sugar.

Stevia or inulin can be replaced by other low-calorie sweeteners to achieve a healthy product with a low glycaemic index. The World Health Organisation (WHO) recommended in 2015 to reduce the content of free sugars in our diet.

The fibre we need
Coffee grounds are mainly composed of dietary fibre (47%), fat (24%), polysaccharides (13%) and protein (11%). According to WHO recommendations, consuming 25 grams of fibre per day provides major health benefits and helps to reduce the risk of chronic non-communicable diseases such as obesity and diabetes, which also aggravate other pathologies such as covid-19.

According to the European Food Safety Agency (EFSA), the average fibre intake in Europe is 12.5 grams per day, half of what is recommended for optimal health. Therefore, the consumption of coffee grounds as a food ingredient can contribute to the necessary increase in dietary fibre intake.

The coffee fibre present in these biscuits can ferment in the gut and release antioxidant and anti-inflammatory compounds that contribute to good gut health. They are a natural source of molecules considered antioxidant fibre, such as melanoidins.

In a study conducted by our research group, we observed that more than half of the fat from coffee grounds is excreted in the faeces and 77% of the unsaturated fatty acids remain bio-accessible to the body.

Helps you sleep better
The health benefits of coffee grounds do not stop at the intestine. These biscuits may also be suitable for regulating the biorhythm.
Diet and the amount of physical activity during the day are factors that determine the quality of sleep. Too little or too little sleep can negatively affect health. It is recommended to sleep 7-9 hours to ensure good health. Biscuits made using coffee grounds as a food ingredient or dietary fibre extracted from coffee grounds can have a positive effect on circadian rhythm and sleep quality.

Reducing food waste
The Food and Agriculture Organisation of the United Nations (FAO) has established a hierarchy for reducing food waste in the form of an inverted pyramid.

FAO´s food waste reduction hierarchy pyramid

The use of dregs and their constituent dietary fibre as an ingredient for human consumption has been accepted by EFSA in 2021, during the current covid-19 pandemic. Its application will contribute to nutritional security in line with the zero-waste philosophy, placing it at the top of the pyramid of strategies proposed by the FAO. Kaffebueno, for example, markets dietary fibre and oil from coffee grounds for use in food and beverages.

Shoe soles, cosmetics and energy
Beyond the popular household uses of coffee grounds, they are also used as a raw material, contributing to a more sustainable use of natural resources, in different industries with a high economic impact. Coffee grounds are used in the manufacture of shoe soles, coffee cups, furniture and tiles, jewellery, cosmetics containing the oil isolated from coffee grounds, and in the energy industry as biofuel and pellets.

While coffee grounds are one of the two most abundant by-products of roasted coffee beverage processing and brewing, other equally abundant by-products are produced on the journey from plant to cup and need to be properly managed in order to achieve a more sustainable food chain and contribute to global nutritional security. How to make the best use of these is the subject of another publication.

Authors

* María Dolores del Castillo Bilbao
CSIC Research Scientist, Biochemist and Dr. in Food Science and Technology, CIAL-CSIC Institute of Food Science

** Amaia Iriondo De Hond
Postdoctoral Researcher, graduate in Biochemistry and PhD in Food Science, CIAL-CSIC Institute of Food Science Research