Abstract
To solve the difficulty of lignocellulose hydrolysis and the formation of crusted scum in anaerobic fermentation, various parts of corn stover, i.e., pith, rind and leaf, were subjected to a two-phase processing including aerobic hydrolysis (AH) and anaerobic fermentation. The results showed that AH significantly broke down the lignin structure of the various components of corn stover and increased the rate of lignin degradation. After 16 h of AH, the lignin degradation rates of the pith, rind and leaf were 4.20%, 3.91% and 4.90%, respectively, and the acetic acid produced accounted for more than 60% of the total amount of volatile fatty acids (VFAs) and ethanol. After hydrolyzing the pith and rind for 12 h and the leaf for 8 h, the maximum methane yields of fresh mass volatile solid (VS) were 323 mL g−1, 251 mL g−1 and 264 mL g−1, respectively, which were increased by 35.02%, 30.05% and 8%, respectively, while the fermentation cycle of T90 (90% of the total gas production) was shortened by 4–5 days. After hydrolyzing the rind and leaf for 12 h and the pith for 16 h, the thicknesses of the scum layer were only 7.1%, 13.6% and 18%, respectively, of that of the untreated group, indicating that AH coupled with anaerobic fermentation can effectively degrade lignin, reduce the thickness of the scum layer and increase the methane yield.
Highlights
The use of anaerobic fermentation technology to convert stover waste into biogas with high calorific value is an effective way to solve energy and environmental problems and has important economic and social benefits [1,2]
Treatment(the group adjusted providewas an appropriate was added to each reactor, and the pH of aerobic hydrolysis (AH) treatment group were adjusted to provide an appropriate anaerobic environment for the microorganisms; the reactor without AH was supplemented with 1,750 ml of inoculum to keep the amount of inoculum at the same level as in the other treatments
In the hydrolysis and acid production stage, complex polymer organic matter is hydrolyzed into monomers, whichorganic are thenmatter converted to volatile fatty acids (VFAs) into and
Summary
The use of anaerobic fermentation technology to convert stover waste into biogas with high calorific value is an effective way to solve energy and environmental problems and has important economic and social benefits [1,2]. Energies 2019, 12, 381 to form a crust that impedes the separation and emission of biogas and reduces the accessibility of the substrate to anaerobic microorganisms, as well as the effective volume of the reactor, seriously affecting the continuous gas production and long-term operation of the reactor [5,6,7]. A variety of measures, e.g., composting pretreatment, an appropriate increase in the fermentation temperature, a suitable substrate concentration, smaller substrate particle size, and anti-encrustation reactor have been employed, and it has been shown that the thickness of the crusted scum layer can be reduced to some extent [17,18,19], still with unsatisfactory overall effectiveness. AH, lignocellulose, gas production from anaerobic fermentation, and the scum layer were investigated to find the suitable duration of AH to maximally improve the methane yield and comprehensive utilization efficiency of corn stover while providing process parameters for the production of biogas from corn stover
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