The Use of a Screw Press to Maximize the Liquid Fraction Extracted from Fruit and Vegetable Wastes for Methane Production

Abstract Fruit and vegetable waste (FVW) consists in a significant challenge in terms of waste management around the world. Anaerobic digestion (AD) represents a potentially effective solution as FVW is composed largely of biodegradable material. This study investigates the use of a screw press to extract a liquid fraction from the FVW for subsequent anaerobic digestion. Different pressure (10- 30- 60 psig) and speed (5- 20- 33 rpm) were tested with the best performance at 60 psig and 20 rpm, showing 61% of the FVW mass obtained as a liquid fraction. Under these conditions, the liquid fraction represented 39% of the organic content from the FVW. Various amount of water (10 – 200% w / w) were added to the solid fraction in a 24 h (h) maceration step in order to further extract the organic content from the solid. An addition of 50% of water to the solids allowed for an additional 17% recovery of organic content in the liquid fraction. A final mass balance showed that 56% of the organic content of the FVW was transferred into the liquid fraction, while leaving 44% of the initial FVW organic content in a solid fraction amounting to only 20% of the initial mass of FVW, requiring further processing. Finally, methane yield confirmed that most of the FVW liquid fraction was biodegradable with a value of 507 ± 14 L STP CH 4 / gTVS. Graphical Abstract