Combined heat treatment and acid hydrolysis of cassava grate waste (CGW) biomass for ethanol production

The effect of combined heat treatment and acid hydrolysis (various concentrations) on cassava grate waste (CGW) biomass for ethanol production was investigated. At high concentrations of H2S04 (1-5 M), hydrolysis of the CGW biomass was achieved but with excessive charring or dehydration reaction. At lower acid concentrations, hydrolysis of CGW biomass was also achieved with 0.3-0.5 M H2SO4, while partial hydrolysis was obtained below 0.3 M H2SO4 (the lowest acid concentration that hydrolysed CGW biomass) at 120°C and 1 atm pressure for 30 min. A 60% process efficiency was achieved with 0.3 M H2SO4 in hydrolysing the cellulose and lignin materials present in the CGW biomass. High acid concentration is therefore not required for CGW biomass hydrolysis. The low acid concentration required for CGW biomass hydrolysis, as well as the minimal cost required for detoxification of CGW biomass because of low hydrogen cyanide content of CGW biomass would seem to make this process very economical. From three litres of the CGW biomass hydrolysate obtained from hydrolysis with 0.3 M H2SO4, ethanol yield was 3.5 (v/v %) after yeast fermentation. However, although the process resulted in gainful utilization of CGW biomass, additional costs would be required to effectively dispose new by-products generated from CGW biomass processing.