Chemical composition and value-adding applications of coffee industry by-products: A review

Processing urban waste is becoming a major challenge, with the current state and forecasted increase in urbanisation. Finding novel approaches to reduce and recycle this waste, using value-adding applications, is paramount if we are to meet the needs of a growing population. Organic waste is of particular concern, as much of this can be treated and recycled for horticulture practices, but most find their final sink in landfill. With coffee now the second largest commodity worldwide, recycling these nutrient-rich by-products could reduce the amount of organic waste sent to landfill, whilst producing value adding products. Some chemical compounds present in these by-products, such as caffeine, tannins and chlorogenic acid are of ecotoxicological concern and can limit their value-adding applications. The aim of this literature review was to 1) characterise the waste obtained from the coffee industry; 2) outline the current value adding applications; 3) highlight limitations that prevent full utilization of coffee by-products and 4) discuss possible solutions that could maximize by-product utilization and ameliorating their negative environmental impacts. It was concluded that full utilization of these by-products is not always achieved, even though there is evidence to support their potential. This was mainly due to a lack of infrastructure and cross-chain networks between applications.