CO-PYROLYSIS of agricultural waste and estimation of the applicability of pyrolysis in the integrated technology of biorenewable hydrogen production

Abstract

For the production of biorenewable hydrogen, the possibility of pyrolysis of agricultural waste, namely cow manure (CM) and stems of weed Amaranthus retroflexus L. (AR), as well as their mixtures in a ratio of 1:1, 2:1 and 4:1, was investigated. Thermogravimetric analysis was carried out at a heating rate of 10 °C/min in the temperature range from 40 °C to 1000 °C. It was shown that the thermal decomposition of agricultural waste in an inert environment is characterized by three main stages, the most significant of which is in the temperature range from 145 to 410 °C, at which the maximum yield of volatile components occurs. Pyrolysis was carried out at a temperature of 550 °C and a heating rate of 10 °C/min. During the pyrolysis of CM and AR mixture, the material balance was on average as follows: 36.95% pyrolysis liquid, 24.99% syngas and 38.06% biochar, and the maximum hydrogen concentration in the pyrolysis gas was 21.17% with CM to AR ratio of 4:1. With this ratio, the hydrogen yield was 12.1% higher than when using a mixture of CM and AR with a 1:1 ratio. An increase in the proportion of AR in the mixture led to the enrichment of the pyrolysis liquid with phenolic compounds. The obtained high content of fixed carbon (47.52%) in biochar is attractive for its use as soil additives. For further research on increasing the yield of gaseous hydrogen from biomass, a scheme of bio-thermochemical processing was proposed, involving a combination of dark fermentation and pyrolysis.