Anaerobic digestion (AD) is one of the most popular technologies to convert organic residues into renewable energy. The use of additives has been shown to increase the process stability and degradation efficiency during AD. However, little attention has been paid to the associated fertilizer production. Thus, this study aims to simultaneously investigate the impact of biochar and lignite on AD and fertilizer production of dairy manure in semi-continuous experiments. Results show that compared to the biogas production rate (BPR) of the reference (394.01 +/- 0.39 lN/(kgVS center dot d), lignite can increase BPR by 4.98%, whereas no impact on BPR was detected due to biochar addition. This indicates that higher O/C and H/C ratios attributed to lignite are a dominant factor influencing BPR, while high specific surface area is not beneficial. Nitrogen yield in the solid phase was increased by 19.47% (lignite) and 14.65% (biochar), significantly promoting the utilization of digestate as solid nitrogen fertilizer.
