Bioreactor Feeding Strategies to Improve Biogas Production and Pig Slurry Management Flexibility

Abstract

Pig slurry (PS) management is a challenge that needs appropriate strategies. Anaerobic digestion (AD) has proved to be an interesting option to follow when it comes to livestock effluent management. Although this technology is well established, it is crucial to investigate different scenarios that demonstrate its suitability to motivate farmers to adopt new strategies for PS management. Previous research, based on a daily feeding regime and a 2-day starvation-induced period, investigated the impact of feast/famine cycles on the AD process. There was evidence of a positive link between AD performance and the starvation regime. From this assumption, new scenarios were designed combining different feeding frequencies: a) one daily feeding (F1) and six feedings per day (F6), b) two days of starvation with one feeding (S1) and with six feedings (S6). The operational parameters were settled in advance: organic loading rate (1.5±0.2 g VS/Lreactor.d), hydraulic retention time (15 days), and mesophilic conditions (37±1 ºC). The results obtained in this work indicate a significant improvement (P < 0.05) of 92% in specific methane production when comparing the trial F1 with F6. VS reduction remained constant in F1 and F6, but the starvation period (S1) led to an increase in VS reduction compared to both F1 (27%) and F6 (33%). The results obtained are in agreement with the previous work conducted by the authors. This study highlights how feeding frequency and starvation affect biogas production, assessing their effectiveness on biogas yield. This tool will give farmers a key decision factor to make an evidence-based decision and can work as a contingency planning strategy, aligning their PS management needs with AD versatility.