Long-Term Mesophilic Anaerobic Co-Digestion of Swine Manure with Corn Stover and Microbial Community Analysis

Abstract

Long-term anaerobic co-digestion of swine manure (SM) and corn stover (CS) was conducted using semi-continuously loaded digesters under mesophilic conditions. A preliminary test was first conducted to test the effects of loading rates, and results indicated the 3 g-VS L^-1 d^-1 was the optimal loading rate. Based on the preliminary results, a verification replicated test was conducted with 3 g-VS L^-1 d^-1 loading rate and different SM/CS ratios (1:1, 2:1 and 1:2). Results showed that a SM/CS ratio of 2/1 was optimal, based on maximum observed methane-VS_des generation and carbon conversion efficiency (72.56 ± 3.40 mL g^-1 and 40.59%, respectively). Amplicon sequencing analysis suggested that microbial diversity was increased with CS loading. Amino-acid-degrading bacteria were abundant in the treatment groups. Archaea Methanoculleus could enhance biogas and methane productions.

Keywords: Amplicon sequencing; biogas; farm waste; semi-continuous digesters; swine manure.

Figure 1

Biogas (A) methane (B) production rates of the control (C1-C3) and treatment digesters, periods a and b were when the digesters were loaded with 2 and 3 g-VS L⁻¹ d⁻¹, and period c was when all digesters were loaded following the experiment design.

Figure 2

Variation of biogas (A) and methane (B) production of control and treatments in Test 2.

Figure 3

The pH value in different treatments in Test 2.

Figure 4

Relative abundance of main taxa at phylum level.

Figure 5

Relative abundance of main taxa at genus level. Uncultured genus microbial was showed family level within bracket because of considerable abundance and importance degree.