Effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers

Abstract

In order to enhance the biogas production and provide nitrogen sources for the growth of microorganisms, experiments on urea ammonia pretreatment of corn stovers were implemented at (35±1)°C to investigate the effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers. This study assessed the effects of urea ammonia contents (2%, 4%, and 6%) and moisture contents (30%, 50%, 70% and 90%) on the physical structures of lignocelluloses and the efficiency of biogas production from anaerobic fermentation of corn stovers. The results indicated that the methane production reached 230.31 mL/g VS (volatile solids) at pretreatment with 4% urea ammonia and 70% moisture contents for the batch anaerobic fermentation, which was 26.6% higher than that of the untreated group. The degradation rates of cellulose and hemicellulose were 66.34% and 75.47% after the anaerobic fermentation, respectively, which were about 22.6% and 20.9% higher than that of the untreated group, respectively. Thus, it was concluded that urea ammonia pretreatment can improve the efficiency of biogas production from anaerobic fermentation of corn stovers.

Biomethane Yield, Physicochemical Structures, and Microbial Community Characteristics of Corn Stover Pretreated by Urea Combined with Mild Temperature Hydrotherm

“…During the pretreatment, the initial pH of CS dropped rapidly from 6.9 to 5.4. However, after 24 h, pH slowly escalated to 5.9 and stabilised for nearly 24 h, finally settling at a slightly increased 6.3 after 96 h. The trend in pH changes was similar to the result reported by Li et al [ 13 ]. The reason why pH value dropped at the initial 24 h is that the water exhibits acid properties at high temperatures.…”

“…Urea is well known and widely used as a fertilizer, but, little is known on its ability to serve as a pretreatment reagent for lignocellulosic wastes, including for wheat straw, CS, softwood spruce and hardwood birch [ 13 , 14 , 15 ]. Compared to other alkaline reagents, using urea has the following advantages: (i) relative cheap price and easy application and use; (ii) as a pretreatment reagent, its nitrogen source assists with adjusting the carbon-to-nitrogen ratio (C/N) of CS—which would otherwise be added during the AD process [ 16 ] and (iii) increases fertiliser value of N-digestate when added during pretreatment [ 17 ].…”

Co-Fermentation of Edible Mushroom By-Products with Soybeans Enhances Nutritional Values, Isoflavone Aglycones, and Antioxidant Capacity of Douchi Koji

“…The above results were in agreement with Zhang et al [2], who found that the AN content increased noticeably during the fermentation of natural-type and artificial-type Yongchuan Douchi. It was reported that the increase in the AN content might be related to the nitrogen compounds generated by the protein degradation in the raw materials [21]. Additionally, urea, a nonprotein nitrogenous compound, also plays a key role in increasing the AN content, through the decomposition of urease-producing microorganisms, such as Pseudomonas sp., into volatile compounds of ammonia [2,22].…”

Determining Optimal Temperature Combination for Effective Pretreatment and Anaerobic Digestion of Corn Stalk

“…Among different alkali chemical pretreatment methods, ammonia solution, urea, NaOH, KOH, Ca(OH) 2 and deep eutectic solvent (DES) are commonly used chemical reagents. Ammonia solution and urea pretreatments can cause ammonia inhibition in the AD reactor system, which will thus reduce biogas production [18,19]. From an economic point of view, the KOH reagent is actually too expensive to be suitable for pretreatment.…”