Evaluation of a leach bed reactor for the anaerobic digestion of drylot collected cattle manure

Abstract

Conventional anaerobic digestion (AD) technologies are not appropriate for processing drylot collected manure without excessive water addition. An alternative AD approach, the leach bed reactor (LBR), may facilitate the digestion of drylot manures with minimal water use but leach bed reactors (LBRs) are known to experience hydraulic failures with manure wastes. The addition of a top sand layer to LBRs is investigated to facilitate the processing of drylot cattle manure containing up to 90% total solids (TS) without hydraulic failure. Here, LBRs were operated to overcome clogging issues and assess the extent of hydrolysis of organic matter in the manure. The system was operated as a batch process with a digestion time of 42 days. The LBRs showed a mean total chemical oxygen demand (COD) reduction of 51.6% and a total volatile solids reduction of 44.7% in manure. Biochemical methane potential tests on leachate indicated a mean methane yield of 0.13 L CH4/g COD leached. The appropriate operational time for the system was found to be 14 days.