Anaerobic digestion performance of sweet potato vine and animal manure under wet, semi-dry, and dry conditions

Abstract

Sweet potato vine (SPV) is an abundant agricultural waste, which is easy to obtain at low cost and has the potential to produce clean energy via anaerobic digestion (AD). The main objectives of this study were to reveal methane production and process stability of SPV and the mixtures with animal manure under various total solid conditions, to verify synergetic effect in co-digestion of SPV and manure in AD systems, and to determine the kinetics characteristics during the full AD process. The results showed that SPV was desirable feedstock for AD with 200.22 mL/g VSadded of methane yield in wet anaerobic digestion and 12.20 Lmethane/Lworking volume in dry anaerobic digestion (D-AD). Synergistic effects were found in semi-dry anaerobic digestion and D-AD with each two mixing feedstock. In contrast with SPV mono-digestion, co-digestion with manure increased methane yield within the range of 14.34–49.11% in different AD digesters. The values of final volatile fatty acids to total alkalinity (TA) were below 0.4 and the values of final pH were within the range of 7.4–8.2 in all the reactors, which supported a positive relationship between carbohydrate hydrolysis and methanogenesis during AD process. The mathematical modified first order model was applied to estimate substrate biodegradability and methane production potential well with conversion constant ranged from 0.0003 to 0.0953 1/day, which indicated that co-digestion increased hydrolysis efficiency and metabolic activity. This work provides useful information to improve the utilization and stability of digestion using SPV and livestock or poultry manure as substrates.

Biomethane Potential of Selected Organic Waste and Sewage Sludge at Different Temperature Regimes

“…The digestion was conducted in wet conditions, and the TS content of the final prepared mixtures (when inoculum was added) was within the range 3.22-5.54%. As reported, there is wet digestion when the TS of final mixtures is lower than 10%, whereas higher values correspond to the semi-dry (TS = 10-15%) and dry (when TS is about 20% and higher) digestions [26,27]. Blank control sample digestion (standalone inoculum) was also done (Figure 1).…”

High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance

“…Agricultural residues with a high lignocellulosic content and a low moisture content may represent an excellent potential energy resource [82] to produce biogas as a valuable fuel if the proper conversion can be attained at a reasonable cost under a solid-state configuration. In addition, co-digestion with manures may take advantage of the synergistic effects reported by several authors [83][84][85][86], particularly when the solid content of the system is increased. However, some difficulties still need to be solved, such as the higher degradation time needed, the high inoculation rate required to start up this process, and the low degradability of lignocellulosic biomass.…”

The impact of thermal pretreatment on various solid-liquid ratios of palm oil mill effluent (POME) for enhanced thermophilic anaerobic digestion performance

“…The total volume of biogas produced by the treated 100S solid loading was obtained as 970.00±2.89 mL , which results in 137 mL more biogas than the untreated 100S solid loading. Another explanation for the reduction in biogas production at higher solid loadings is attributable to the decrease in water content and the associated least effective transport and mass transfer conditions whereby the microorganisms cannot thrive in an environment with limited soluble substrates, thus making the anaerobic digestion process less efficient (Le Hyaric et al, 2012;Xu et al, 2014;Zhang et al, 2018).…”