New approach of characterizing fruit and vegetable waste (FVW) to ascertain its biological stabilization via two-stage anaerobic digestion (AD)

Abstract

Assessing some of the very basic physical and chemical properties, such as moisture content, specific gravity, fixed solids, volatile solids, pH, VFA/Alkalinity, hydrolyzable solid matter, orthophosphate concentration, sulfate concentration, and inorganic nitrogen concentration, of fruit and vegetable waste (FVW) is fundamental towards its efficient management. The present study establishes a cost-effective measurement technique/protocol to characterize FVW that not only helps in understanding the nature of the FVW generating at a particular place, but also helps in designing the appropriate waste-to-energy technology that ameliorates the generated FVW. As such, the characterization results in the present study were used to design a novel two-stage hybrid anaerobic digester. The proposed measurement technique/protocol can be very easily replicated at any standard chemical laboratory having basic facilities. Besides, it can also be extended to characterizing any such organic solid waste (agricultural waste) that resembles the nature of FVW, and with the slightest of modification can also be used to characterize organic fraction of the municipal solid waste (OFMSW) on the whole. The results of the chemical characterization for the fresh, 24-h old, 48-h old, and 72-h old FVW matter indicated the suitability of 24-h old FVW matter to undergo the highest degree of stabilization via anaerobic digestion (AD). Results from subsequent batch studies, pertaining to the stabilization of the aforesaid four FVW types via the designed two-stage anaerobic digester, corroborated this observation. AD of 24-h old FVW yielded the highest biogas production rate (12.5 L d−1), and the highest COD-removal percentage (90%), under the shortest batch period (48–60 h).