Coffee grounds are often applied to the soil directly by many farmers and gardeners as fertilizers in their farms. Coffee grounds are rich in nitrogen as well as phosphorus, potassium and other micronutrients. It is commonly used as a slow-release fertilizer which the nutrients are release as it breaks down. Other than fertilizer it has also been used in pest management， as a deterrent against snails and birds. This makes it sounds like a great idea for farming. However if the spent coffee grounds are not composted and added to the soil to the soil directly, it may actually bring negative effects to the plants and soils instead.
1. Effects on The Plants
The reason of this concern is the presence of caffeine in coffee beans. When coffee leaves fall, the caffeine in the leaves have inhibitory effects on germination of other plants and reduces competition with other plants. Spent coffee grounds contain chlorogenic acids, tannins and caffeine that impose toxicity to plants and soils. Caffeine possesses phytotoxicity and inhibits growth of the plants as well as germination. Studies show that the use of a high dose of caffeine on plants would eventually lead to stunted plant growth. One of the solutions that helps reduce the negative impact is through composting spent coffee grounds before adding to the soil.
2. Environmental Impact
Over a billion cups of coffee are consumed everyday worldwide, leading to spent coffee grounds ending up in garbage dumps as waste. This waste is not properly disposed and commonly being left in a landfill, generating tonnes of methane gas from its decomposition process in the landfill. Methane is a greenhouse gas that could be way more harmful than carbon dioxide to the environment. The direct use of spent coffee grounds is not as environmental friendly as how some of us thought, as the presence of bioactive compounds causes the decomposition of spent coffee grounds highly polluting due to the release of methane in the process. Caffeine and polyphenols have a high toxicity rate for the soils and consequently causes environmental hazards. An alternative to lower the environmental impact and toxicity could be through vermicomposting, in order to yield a nutrient source that has beneficial effects on plant heath and soil quality.
3. Go For Vermicomposting!
Earthworms love coffee grounds! Coffee is one of the most consumed beverages in the world and there is a massive amount of coffee ground waste produced every single day. However there is a lack of waste management of spent coffee grounds especially in developing countries. Spent coffee grounds are in fact rich in nutrients needed by plant growth. Vermicomposting of spent coffee grounds turns the waste into a form that is more environmental-friendly and it makes the nutrients more readily absorbed by the plants, causing less negative effects to the soil quality.