Efficient Biogas and Ethanol Production from Safflower Straw Using Sodium Carbonate Pretreatment
journal contributionposted on 18.11.2016, 00:00 by Seyed Sajad Hashemi, Keikhosro Karimi, Mohammad Javad Nosratpour, Ilona Sárvári Horváth
Safflower straw, an agricultural lignocellulosic waste, was used for biogas and bioethanol production. Prior to bioconversion, the straw was pretreated with 0.5 and 1 mol/L sodium carbonate (Na2CO3) at 120, 150, and 180 °C for 1–5 h, resulting in a liquid fraction containing hemicellulosic sugars and a solid fraction mainly containing cellulose. Two scenarios were followed: (I) subjecting both solid and liquid fractions to biogas production and (II) subjecting the solid fraction to bioethanol production and the liquid fraction to biogas production. The highest yield of glucose was 91.4%, achieved after pretreatment at 180 °C with 0.5 mol/L Na2CO3 for 5 h, as compared to that of 22.1% for the untreated substrate. The ethanol yield of untreated straw was 11.1%, and it was improved to 58.1% after alkali pretreatment at 180 °C with 1 mol/L Na2CO3 for 2 h. The highest methane yield obtained was 139.6 N mL/g of volatile solids (VS) after pretreatment at 120 °C with 0.5 mol/L Na2CO3 for 1 h, while that from the untreated straw was only 92.1 N mL/g of VS. On the other hand, from the liquid fraction, a maximum of 88.2 N mL/g of VS of methane was produced after pretreatment with 0.5 mol/L Na2CO3 at 180 °C for 2 h. The highest equivalent gasoline (on the basis of 1 ton of safflower straw) for scenario I was 113.9 L, obtained by pretreatment at 120 °C with 0.5 mol/L Na2CO3 for 1 h. This value for scenario II was 100.0 L, observed after pretreatment at 180 °C with 1 mol/L Na2CO3 for 2 h. The equivalent gasoline for untreated straw for scenarios I and II was 93.6 and 17.1 L, respectively.