Studies have shown
that anaerobic digestion (AD) has an effect
on the liquid and solid product property of sequential pyrolysis,
but its influence on the gaseous products is lacking. In this study,
syngas produced by pyrolysis from three raw organic solid wastes and
the corresponding digestates, i.e., food waste, vinasse, and cow manure
were investigated. AD causes a decrease in the contents of volatile
solid, fixed carbon, C, H, and N and an increase in the S content.
The weight loss of the wastes mainly occurs at 200–550 °C
during the pyrolysis and the loss of the food waste and vinasse is
higher than that of cow manure. In the carbon (C)-containing gas,
AD leads to a decrease in the CH
4
content of the syngas,
implying that the heat values of the digestates are lower than that
of the raw substrates. After AD, the total amount of nitrogen (N)-containing
gas from the vinasse increases by 40.1%, while that from cow manure
decreases by 14.1%. On the contrary, the total amount of sulfur (S)-containing
groups in the syngas from vinasse drop by 22.0%, while that from cow
manure increases by 9.1%. In addition, slight changes in the C-, N-,
and S-containing gases are found from food waste. The results indicate
that AD has a different effect on the N- and S- containing gaseous
groups from different organic solid wastes, and the mechanisms deserve
further investigation. The findings supply a theoretical foundation
for environmental-friendly application of syngas from the digestates.