h i g h l i g h t s Pollutant emissions during hydrochar–lignite co-pyrolysis were first investigated. Lower emissions of NH 3 and HCN were observed during hydrochar pyrolysis compared to lignite. Synergistic interactions decreased NH 3 and HCN formation and increased N 2 yield. Hydrochar addition in lignite suppressed PAHs emissions, especially high-ring PAHs. a b s t r a c t Nitrogen conversion and polycyclic aromatic hydrocarbon (PAH) formation during rapid pyrolysis of hydrochar, lignite and hydrochar–lignite blends have been investigated within a temperature range of 600–900 °C. The results showed that in comparison to lignite, a higher percentage of hydrochar nitrogen was retained in the char, and less NH 3 and HCN were formed during pyrolysis. During pyrolysis of the individual hydrochar and lignite components, yields of NH 3 and HCN reached a maximum at 800 °C and then decreased with increasing temperature. Addition of hydrochar to the lignite increased yields of total HCN and NH 3 at low pyrolysis temperatures (6700 °C), but suppressed their formation at high temperatures (P800 °C). Synergistic interactions in hydrochar–lignite blends significantly decreased the total nitrogen percentage in the char, and promoted the conversion into N 2 at temperatures P800 °C. These synergistic interactions increased with (but were not linearly proportional to) increasing temper-atures and hydrochar ratios in the blends. With regard to PAH emissions, relatively less high-ring PAHs were present in tars from pyrolysis of hydrochar–lignite blends than in tars from pyrolysis of lignite alone. These findings suggest that co-processing of hydrochar–lignite blends for energy production may have the additional benefit of reducing emissions of nitrogen pollutants and PAHs.