A review of sustainable technologies for bio-char production from biomass

Abstract

The present research work is aimed to conduct the pyrolysis of the shredded cotton stalk, as feed stalk, considering more economical for the preparation of raw material, as compared to ground biomass to be used as feed stalk. Keeping the above background in mind, the present study on the development of a small capacity (5 kg) fixed bed pyrolyser for shredded cotton stalk as feed stalk A total number of sixteen experiments were performed on the pyrolysis of shredded cotton stalk at four levels of temperature 200, 300, 400 and 500°C and four residence times of 60, 120, 180 and 240 min respectively. Three main products of pyrolysis of shredded cotton stalk biomass were determined in terms of bio-char, bio-oil and pyro-gas yield. Calorific value of cotton stalk biomass was found as 3685.3 cal/g. The minimum and maximum calorific value of its bio-char was found as 4622.0 cal/g and 8101.3 cal/g at 200°C and 60 min and; 500°C and 240 min temperature and residence time. Thus calorific value was increased by 1.19 times. The quality of bio-char of shredded cotton stalk obtained at 500°C temperature and 240 min is best out of the all experimental levels of variables of temperature and residence time. At this temperature and residence time, the quality of bio-char in terms of calorific value, nitrogen content, carbon content and C/N ratio were found as 8101.3 cal/g (33.89 MJ/kg), 1.56%, 79.30%, and 50.83 respectively. The minimum and maximum value of bio-oil yield was found as 10.2% and 19.0% at 200°C and 60 min and; 500°C and 240 min temperature and residence time respectively. The minimum and maximum value of pyro-gas yield was found as 19.6% and 47.8% at 200°C and 60 min and; 500°C and 240 min temperature and residence time respectively. Slow pyrolysis process is the most suitable process for bio-char production. The quality of bio-char of shredded cotton stalk obtained at 500°C temperature and 240 min is best out of the all experimental levels of variables of temperature and residence time. At this temperature and residence time, the quality of bio-char in terms calorific value (8101.3 cal/gor 33.89 MJ/kg), nitrogen (1.56), carbon (79.30), and C/N ratio (50.83) respectively. The quality of biochar for various applications are discussed along with different quality parameters.