Abstract: Urban agriculture is a highly concerned issue during the period of rapid urbanization in Vietnam. Research aims to propose a cultivation process for cultivating oyster mushrooms, utilizing coffee grounds from coffee businesses as a resource. This approach promotes circular economy principles, generating economic benefits for households while protecting the environment and being suitable for urban areas. The study conducted experiments on grey oyster mushrooms using different mixtures of coffee grounds and rubber wood sawdust at the following ratios: 0%, 25%, 50%, 75%, and 100% coffee grounds/rubber wood sawdust, filled into bags with a weight of 1.2kg. The research results showed that disease infection rates were mild in the 0% and 25% mixture ratios, while the remaining ratios exhibited moderate to severe infection levels. The highest mushroom yield was observed in the mixture ratio of 25% coffee grounds, with an average number of mushroom ears per bag reaching 29.7grams/bag, the dry weight is 63.8 grams/bag, with an average size ranging from 3 to 14 cm and a moisture content of 79.5%. The fastest colonization speed on the substrate is achieved by 25%, 50% coffee grounds blend, which fully colonizes the bag in a period of 25 to 35 days, the shortest time compared to the 75% and 100% coffee grounds blends, which take 40 to 45 days. The experimental results show that the 25% coffee grounds: 75% rubber sawdust blend is suitable for urban mushroom cultivation models and can be expanded on a large-scale farm, contributing to minimizing environmental pollution, utilizing limited urban land area, and providing high economic efficiency.

Coffee is among the favorite drinks in Vietnam and many other countries. Production and consumption of coffee have released a huge amount of spent coffee ground. This study aimed to determine phenolic acids and fatty acids of spent coffee grounds collected in Ho Chi Minh city and how phenolic acid profile was affected by different environmentally friendly extractants. The results showed that average level of chlorogenic acid in ethanol/water extracts (840.4 779.9 ug/g) was significantly higher compared to water extracts (300.0 ug/g). Furthermore, the average total level of phenolic acids in ethanol/water extracts (1215.3 ug/g dry weight) was greater than that in the water extracts (779.9 ug/g dry weight). This indicated that ethanol/water outperformed water in regard to extraction of phenolic acids in the spent coffee grounds. Oil extracted from the spent coffee grounds was rich in linoleic acid (61 ug/g) and palmitic acid (47 ug/g). The findings of our study showed that the spent coffee grounds originating in Vietnam are a good source of phenolic acids and polyunsaturated fatty acids that could be utilized for food and nutraceutical production.