Coffee is one of the most consumed drinks in the world. It is grown in more than 70 countries and produces more than 16 billion pounds of beans annually. That’s a lot of beans… and if they’re used just once and thrown away, that also amounts to a huge amount of waste.
If you drink a lot of coffee or have worked in a coffeehouse, you’ve probably looked at the enormous amount of coffee grounds thrown away after one use and wondered, “Can’t this be used for something?” You’re not the only one; researchers around the world have wondered the same thing and investigated the problem. The good news: coffee grounds DO have value! What possible uses for used coffee grounds have been found?
How to use used coffee grounds
1. Remove lead from water
Researchers at Japan’s Kinki University investigated the possibility of using coffee grounds to remove lead from drinking water and found that it was indeed not only possible, but that it actually worked quite well. [1] The prospect of using coffee grounds, an all-too-common waste product, for a purpose as useful as removing lead from drinking water is an exciting idea!
2. Biodiesel production
You may have heard of diesel vehicles being converted to run on waste grease from fast food restaurants. Wouldn’t it be great if discarded coffee grounds could also be used as an energy source? Maybe.
Researchers from the University of Nevada, Reno discovered that oil extracted from coffee grounds can be converted into biodiesel. Depending on the type, used coffee grounds can contain approximately 15% oil. This may not sound like much, but experts estimate that biodiesel production levels could reach more than 340 million liters, if we take into account all the coffee grounds used in the world. As a bonus, they also found that even after the oil has been extracted, the coffee grounds are still excellent for garden fertilizer, feedstock for ethanol and fuel pellets. [2]
Moreover, the Research Institute of Industrial Science and Technology in South Korea conducted similar experiments and found that coffee grounds were a good candidate for bioethanol and biodiesel production. [3]
3. Improves composting
A 2008 study from Malaysia found that when coffee grounds were added to vermicompost – composting that uses worms – it helped produce more earthworms than just kitchen waste. This is, at least in part, because the coffee grounds increased the nutrient content in the vermicompost. [4] This is easy for everyone to participate in. If you’re not composting, start composting. And if you already are, make sure you throw your coffee grounds into the mix!
4. Agricultural nutrient
It is quite common for gardeners to add used coffee grounds to the garden soil. I had a friend who routinely dumped the remains of his French press into his plant pots. Old wives’ talk? Not entirely, research shows that it is a valuable idea.
In early 2012, Portuguese researchers investigated the impact of adding coffee grounds to lettuce cultivation. The results were astonishing: the carotenoid and chlorophyll content in the lettuce increased, as did the amount of lutein and beta-carotene. There is a ceiling, however, as they also found that the benefits stopped at a 10% limit on the coffee grounds to soil ratio. [5]
In Japan, the National Institute of Vegetable and Tea Science has published information recommending adding coffee grounds to rice cultivation to increase rice yields and nutrient content (in addition to reducing waste in landfills). [6]
5. Source of antioxidants and other nutrients
So why are coffee grounds so useful? Because they are not actually “used up” and still contain valuable nutrients. Earlier this year it was confirmed that coffee grounds still contained antioxidants that could be used for nutritional supplements, food or cosmetics. [7]
In fact, research at Spain’s University of Navarra found that spent coffee grounds actually contain up to seven times as many beneficial antioxidants as brewed coffee! [8]
The logistics of using coffee grounds
References (8)
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- Tokimoto T, Kawasaki N, Nakamura T, Akutagawa J, Tanada S. Removal of lead ions from drinking water by coffee grounds as plant biomass. J Colloid interface Sci. January 1, 2005;281(1):56-61.
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- Kondamudi N, Mohapatra SK, Misra M. Uses coffee grounds as a versatile source of green energy. J Agricultural Food Chem. December 24, 2008; 56(24):11757-60. doi: 10.1021/jf802487s.
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- Kwon EE, Yi H, Jeon YJ. Sequential co-production of biodiesel and bioethanol with coffee grounds. Bioresour technology. May 2013; 136: 475-80. doi: 10.1016/j.biortech.2013.03.052. Epub March 16, 2013.
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- Adi AJ, Noor ZM. Waste recycling: use of coffee grounds and kitchen waste in vermicomposting. Bioresour technology. 2009 Jan;100(2):1027-30. doi: 10.1016/j.biortech.2008.07.024. Epub August 26, 2008.
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- Cruz R, Baptista P, Cunha S, Pereira JA, Casal S. Carotenoids from lettuce (Lactuca sativa L.) grown on soil enriched with coffee grounds. Molecules. February 7, 2012; 17(2):1535-47. doi: 10.3390/molecules 17021535.
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- Morikawa C.K., Saigusa M. Recycling coffee grounds and tea leaf waste to improve the yield and mineral content of paddy grains. J Sci Food Agric. August 30, 2011; 91(11):2108-11. doi:10.1002/jsfa.4444. Epub May 5, 2011.
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- Panusa A, Zuorro A, Lavecchia R, Marrosu G, Petrucci R. Recovery of natural antioxidants from spent coffee grounds. J Agricultural Food Chem. April 11th 2013.
- Bravo J, Juániz I, Monente C, Caemmerer B, Kroh LW, De Peña MP, Cid C. Evaluation of spent coffee obtained from the most common coffee makers as a source of hydrophilic bioactive compounds. J Agricultural Food Chem. December 26, 2012; 60(51):12565-73. doi: 10.1021/jf3040594. Epub December 13, 2012.
†Results may vary. The information and explanations provided are for educational purposes and are not intended to replace the advice of your doctor. If you have a serious medical condition or health problem, consult your doctor.