Zhang DaLei

High-solid Anaerobic Co-digestion of Food Waste and Rice Straw for Biogas Production

Anaerobic co-digestion of food waste (FW) and rice straw (RS) in continuously stirred tank reactor (CSTR) at high organic loading rate (OLR) was investigated. Co-digestion studies of FW and RS with six different mixing ratios were conducted at an initial volatile solid (VS) concentration of more than 3 gVS · L−1. The biogas production, methane contents, degradation efficiency of VS, chemical oxygen demand (COD) and volatile fatty acids (VFAs) were determined to evaluate the stability and performance of the system. The results showed that the co-digestion process had higher system stability and higher volumetric biogas production than mono-digestions. Increase in FW content in the feedstock could increase the methane yield and shorten retention time. The efficiency of co-digestion systems mainly relied on the mixing ratios of FW and RS to some extent. The highest methane yield was 60.55 mL·gV·S−1 · d−1 at a mass ratio (FW/RS) of 3 : 1, which was 178% and 70% higher than that of mono-digestions of FW and RS, respectively. Consequently, the anaerobic co-digestion of FW and RS could have superior stability and better performance than mono-digestions in higher organic loading system.

Comparison of the physical-chemical properties of corn stalk by expansion and chemical pretreatments and their effect on the yield of biogas

The physical-chemical properties of corn stalk were comparatively investigated after 1% of sulfuric acid, 2% of sodium hydroxide and expansion pretreatments, and then their effect on producing biogas of the treated corn stalk were assessed. Three physical-chemical indicators including the reducing sugar yield, the organic components and the microstructures revealed by scanning electron microscopy were detected in this study. The results showed that the conversion rate of the reducing sugar of corn stalk treated with 1% of sulfuric acid was the highest (17.8%), the startup speed of anaerobic zymolysis of corn stalk treated with 2% of sodium hydroxide was the fastest, and the total effect on producing biogas of corn stalk treated with expansion method was the best. The daily gas production rate of corn stalk after expansion pretreatment reached 0.63 m3·m-3·d-1, the 60d total gas production rate reached 5.89 m3·m-3, and the methane content come up to 82.9%. The results obtained in this paper provide a new and effective method to improve by a large amount the biogas yield of corn stalk.