Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis

<div><p>The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum <i>Chloroflexi</i> decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. <i>Methanosarcina</i> absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies.</p></div

Characteristics of the substrates and inoculums.

<p>–Not determined.</p>a<p>FW: food waste.</p>b<p>TS: total solids.</p>c<p>VS: volatile solids.</p>d<p>TAN: total ammonia nitrogen.</p

Taxonomic compositions of bacterial communities at phyla level in each sample retrieved from pyrosequencing.

<p>Taxonomic compositions of bacterial communities at phyla level in each sample retrieved from pyrosequencing.</p

Performance parameters of three reactors with different total solids contents.

a<p>Y_biogas: biogas yield.</p>b<p>Y_methane: methane yield.</p>c<p>VS_r: VS reduction.</p>d<p>SBP: specific biogas production rate based on removed VS.</p>e<p>SMP: specific methane production rate based on removed VS.</p>f<p>BP: volumetric biogas production rate.</p>g<p>MP: volumetric methane production rate.</p

Taxonomic compositions of methanogens at order level in each sample retrieved from pyrosequencing.

<p>Taxonomic compositions of methanogens at order level in each sample retrieved from pyrosequencing.</p

Taxonomic composition of bacterial communities at the genus level for the sequences retrieved from each sample.

<p>Taxonomic composition of bacterial communities at the genus level for the sequences retrieved from each sample.</p