Application of torrefaction for recycling bio-waste formed during anaerobic digestion

The problem of waste recycling becomes more serious every year. As the population grows, the amount of organic bio-waste is increased proportionally. Even the subsequent energy utilization of such bio-waste leaves a huge amount of unprocessed organic mass, as in the case of anaerobic digestion. In this paper, the results of experimental studies of the torrefaction of sewage sludge and animal waste (mixture of horse manure and crop waste) after anaerobic digestion are presented. The aim of this work was to investigate the possibility of applying torrefaction to improve the thermotechnical properties of bio-waste products. The research results showed that the torrefaction allows to improve heating value and hygroscopicity, but with increasing of process temperature these values grow insignificantly. In addition, the conclusion about the ash content value of the bio-waste in which it is effectually to apply torrefaction treatment was made.