Adaptation of continuous biogas reactors operating under wet fermentation conditions to dry conditions with corn stover as substrate

Abstract

Corn stover (CS) is the agricultural by-product of maize cultivation. Due to its high abundance and high energy content it is a promising substrate for the bioenergy sector. However, it is currently neglected in industrial scale biogas plants, because of its slow decomposition and hydrophobic character. To assess the maximum biomethane potential of CS, long-term batch fermentations were carried out with various substrate concentrations and particle sizes for 72 days. In separate experiments we adapted the biogas producing microbial community in wet fermentation arrangement first to the lignocellulosic substrate, in Continuous Stirred Tank Reactor (CSTR), then subsequently, by continuously elevating the feed-in concentration, to dry conditions in solid state fermenters (SS-AD). In the batch tests, the <10 mm fraction of the grinded and sieved CS was amenable for biogasification, but it required 10% more time to produce 90% of the total biomethane yield than the <2 mm sized fraction, although in the total yields there was no significant difference between the two size ranges. We also observed that increasing amount of substrate added to the fermentation lowered the specific methane yield. In the CSTR experiment, the daily substrate loading was gradually increased from 1 to 2 g/L/day until the system produced signs of overloading. Then the biomass was transferred to SS-AD reactors and the adaptation process was studied. Although the specific methane yields were lower in the SS-AD arrangement (177 mL CH/g in CSTR vs. 105 mL in SS-AD), the benefits of process operational parameters, i.e. lower energy consumption, smaller reactor volume, digestate amount generated and simpler configuration, may compensate the somewhat lower yield.

Intensification of Ex Situ Bioremediation of Soils Polluted with Used Lubricant Oils: A Comparison of Biostimulation and Bioaugmentation with a Special Focus on the Type and Size of the Inoculum

“…Shortly, 35 g soil was weighed into a plastic cylinder (the bottom of which was secured with cotton fabric and a rubber band), saturated for 48 h and then placed onto damp sand to drain for 48 h. Soil organic matter was indicated by the weight loss on ignition at 550 • C for 4 h, while carbonate content in soil was measured by combustion at 950 • C for 2 h [48]. Total C and total N in soils were analyzed using a Vario MAX CN Analyzer equipment (Elementar Group, Hanau, Germany) with the operating parameters described in Kakuk et al [49]. For available P determination, the optimized colorimetric method of Franson [50] was used.…”

Anaerobic Digestion Technology for Methane Production Using Deer Manure Under Different Experimental Conditions

“…With TSes of 15% as the limit, AD can be divided into dry AD and wet AD [66]. In general, wet AD produces more biogas than dry AD does [67][68][69][70]. In the process of AD, the TSes of the fermentation material also change with degradation [71].…”

Dry Anaerobic Digestion Technologies for Agricultural Straw and Acceptability in China

“…Straw is characterized by its low bulk density, high-water holding capacity, and poor fluidity, resulting in poor heat and mass transfer, which results in detrimental non-homogeneity of the mixture that degrades digestion performance [29,38]. Mixing is deemed as very important for achieving a good distribution of the substrates, microorganisms, and enzymes in the digester, in order to optimize anaerobic digestion [39]. Ivoachu et al confirmed that recycling percolate in dry anaerobic digestion is a viable method for digesting straw more rapidly and effectively, due to the higher nutrient and microbial concentration in the recycled percolate [38].…”