Research team touts vegetable benefits for used coffee grounds

A study has found that used coffee grounds offer several benefits such as being able to boost vegetable growth when added to compost or fertilizer and as an insect repellent to protect citrus fruit.

The use of a compost pile with 10 percent of it consisting of coffee grounds to grow water spinach in its initial growing period produced water spinach whose weight was larger than regular ones by 105 percent, Lin Shu-i (林淑怡), an associate professor at National Taiwan University's Department of Horticulture and Landscape Architecture, said at an event to present research findings on the use of spent coffee grounds.

After using a compost pile with two percent of it being spent coffee grounds (SCG) to grow bok choy, the length of the vegetable's leaves increased by 13 percent and the weight by 22 percent, Lin said. Adding coffee grounds to compost helps build a nutrient-rich, fertile compost soil but it will take about at least three months before the coffee grounds start decomposing as organic fertilizer, according to Lin.

Field experiments showed that coffee grounds are good for growing 30 to 40 popular leafy green vegetables, Lin noted. However, she added that when adding untreated spent coffee grounds to a compost pile, the volume of the grounds should not exceed 2 percent of the pile because untreated SCGs have detrimental agronomic effects due to a high amount of noxious compounds produced during the fermentation process.

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