Food Waste Recycling and Algal Destruction for Municipalities and Food Plants

Abstract

Algae, food waste (groceries, bakery waste), dairy processing waste (hereafter called dairy waste) and algae comingled with food or dairy waste were digested in Induced Bed Reactor (IBR) anaerobic digesters at mesophilic conditions in trials that ran for about one year; data was collected for 7 months. Algae were harvested from the citys facultative lagoon based 14 MGD wastewater treatment facility to reduce effluent total phosphorus concentration and anaerobic digestion was explored as a method to dispose of the algae. Chemical oxygen demand (COD) removal from the algae was 32 to 62.5% depending on hydraulic retention time. Though the IBR is a high rate digester, in these experiments a long HRT of nearly 40 days gave the best COD removal (62.5%) for algae. COD removal from food waste was about 86%; that from dairy was about 80% and comingling resulted in COD removal of up to 87%. A zeolite based biogas conditioner removed sulfur compounds including H2S and other contaminants from biogas to non-detectable limits (< 0.050 ppmv). The biggest problem with feeding food waste was grinding and materials handling. Otherwise the food waste was good substrate.