Effect of Particle Size on the Aerobic and Anaerobic Digestion Characteristics of Whole Rice Straw

Abstract

The effect of reducing particle size on physical properties, the methane yield and energy flow were investigated through the biochemical methane potential (BMP) experiment of aerobic-anaerobic digestion (AAD) of rice straw (RS). The whole straw was crushed through four sieves of different aperture sizes (1, 3, 5, and 7 mm) to obtain the actual and non-uniform particle size distribution (PSD). The results indicated that the actual particle sizes were normally or logarithmic normally distributed. Reducing particle size could significantly promote the aerobic hydrolysis and acidification process, increase the content of volatile fatty acids (VFAs) from 4408.78 to 6225.15 mg/L and the degradation of volatile solids (VS) from 40.56% to 50.49%. The results of path analysis suggested that particle size reduction played an important role in improving lignocellulosic degradability, which was the main factor affecting methane production with the comprehensive decision of 0.4616. The maximum methane production obtained at 1 mm sieve size was 176.47 mLCH4g−1 VS. The phyla of Firmicutes (61.5%), Proteobacteria (9.3%), Chloroflexi (8.3%), Bacteroidetes (4.1%), Cyanobacteria/Chloroplast (4.6%) were mainly responsible for VFAs production and lignocellulose degradation. However, the net negative energy balance was observed at the 1 mm sieve size due to the increased energy input. Therefore, the optimum sieve size for AAD was 3 mm.

Mechanical pretreatment of lignocellulosic biomass toward enzymatic/fermentative valorization

“… Luo et al. (2021) used this technology to observe the influence of particle size on methane production.…”

“…However, regarding energy consumption, it was the most efficient one. Size reduction also reduced the crystallinity of the biomass from 24.65 to 15.31% for the smallest particle size ( Luo et al., 2021 ). Al Afif and Pfeifer, 2021 used hammer-milled cotton stalks to produce methane.…”

“…After comminution, the minimum particle found was 0.6 μm ( Victorin et al., 2020 ). However, the most common final particle size ranged between 500 and 250 μm ( Luo et al., 2021 ; Maitra and Singh, 2021 ). Table 4 shows the references consulted regarding hammer milling.…”

“…However, it needs large equipment and high residence times to complete the reaction ( Amin et al., 2017 ). Again, owing to the recalcitrant nature of LCB, A.D. is usually performed with previous treatments, so reducing sugars can become more accessible ( Luo et al., 2021 ). Authors have used mechanical treatments before A.D., i.e., Garuti et al.…”

Methane Production from Anaerobic Co-Digestion of Cow Manure and Sugarcane Bagasse Under Mesophilic Condition: Effect of Mixing Ratio

“…[12,18]. SB was dried and grinded and a household grinder reduced its size to (2-3) mm [13]. The samples were then maintained at 4 degrees Celsius for three days to determine their features and feed the anaerobic digesters.…”