Industrial use of bioenergy and high-value molecules extracted from winemaking by-products. Ecological aspects

Abstract

From the concept of circularity, a new industrial revolution is arising where waste as unwanted or unusable material is virtually unknown. In present times, indicators describe the main constraints posed on our world`s future development: population growth, carbon dioxide in the atmosphere, energy consumption, overuse of minerals and natural resources, and shortage of water, which leads to a future zero-waste society. In this context, a study was developed to explore the potential applications of winemaking sub-products, known as grape pomace (GP), which have incomplete exploitation and part of which is dumped as biowaste. In European countries, the winemaking industry converts 22 million tonnes annually of grapes into wine, giving rise to 5 million tonnes of GP as a product. The goal of this research was to examine the antioxidant capabilities of GP polyphenols in order to identify useful industrial uses. With a total phenolic content (TPC) of 86 mg GAE/g DM in Loureiro variety seed and only 35.1 mg GAE/g DM in Vinhão variety, with very significant differences (p < 0.01), GP can offer a wide range of products with high-value bioactive molecules. In the skin fraction, the TPC value was higher in Vinhão variety than Loureiro variety (120 and 24 mg GAE/g DM, respectively). The findings of TPC and the antioxidant activity as determined by DPPH activity are correlated, with r = 0.988 for Vinhão and r = 0.975 for Loureiro. From the seeds of the grape types Loureiro and Vinhão, a high-yield edible oil content of 16.5% and 17.7%, respectively, was found. When compared to other biomass heating values, the heating value results of GP samples after the fat and polyphenol extraction, which are between 16.9 and 17.2 MJ/kg, show that GP extracted residue has the potential for energy recovery. This byproduct offers fresh prospects for alternative industrial uses when taking into account the quantities of GP that are produced each year and its chemical characteristics.