The application of priming, the increase of microbial organic matter turnover by the addition of easily degradable carbon, was investigated for improving biogas production and post-digestion efficiency. Continuously stirred tank main- and post-digesters were operated on manure-based agricultural waste. Potato starch was added as the priming substrate to the post-digester. Addition of 0.2 g VS/L starch every other day increased biogas production from 413 ± 97 to 509 ± 58 mL biogas/day. The increased biogas production exceeds the output from the individual substrates confirming the priming effect. Additionally, the specific biomethane production increased from 74 ± 16 to 116 ± 43 mL/g VS. A shift in microbial community was detected, benefiting lignocellulolytic activities, as degradation of cellulose, hemicellulose and total sugar was enhanced. The results indicate successful application of priming which can improve the overall efficiency of biogas production from manure-based feedstock. Funding Agencies|Swedish Energy Agency [35624-2, P2021-90266]