Effect of vacuum negative pressure aerobic hydrolysis pretreatment on corn stover anaerobic fermentation

Abstract

Lignin degradation restricts corn stover anaerobic fermentation efficiency. The vacuum negative pressure aerobic hydrolysis pretreatment of corn stover was tested, and the optimal combined pretreatment conditions were presented in this paper. Because of the physical characteristics of light weight and large specific porosity of stover, it led to the formation of a scum layer during the fermentation process and thus reduced the gas production rate. In the pretreatment design, the vacuum conditions (0.02-0.08 MPa) and dwell time (5-20 min) were selected to see the changes of volumetric weight, swelling and specific porosity of corn stover, resulting in an increase of the volumetric weight by 7.18%-28.72%, an increase of the swelling by 3.18%-58.59%, and a decrease of the specific porosity by 9.34%-38.59%, as compared with the CK group. Continuous vacuum negative pressure treatment could discharge the air inside the stover destroy the microstructure, and cause the stover to settle more easily during the aerobic hydrolysis process. The optimal aerobic hydrolysis temperature and time were determined to be 39°C and 12.65 h, respectively. With the optimal pretreatment, the corn stover anaerobic fermentation test realized a cumulative methane yield of 260.44 mL/g VS, 22.71% higher than CK group; meanwhile, the hydraulic retention time was shortened by 32.39%.

Comparison of life cycle assessment of large-scale biogas projects with different raw materials in China

“…Then, according to the standardization factor after the standardization weight, eliminate the dimension difference of different impact types, get the standard equivalent environmental impact potential size, intuitive evaluation and analysis [24] . Fossil resource scarcity kg oil-eq 1.02×10 -3 Human carcinogenic toxicity kg 1,4-DB-eq 3.39×10 -3 Human non-carcinogenic toxicity kg 1,4-DB-eq 4.50×10 -7 Marine ecotoxicity kg 1,4-DB-eq 4.06×10 -7 Fine particulate matter formation kg PM2.5-eq 3.91×10 -2 Water consumption m 3 3.75×10 -3…”

“…The current measures to improve the net energy efficiency of biogas engineering are mainly to improve the efficiency of electric energy utilization and reduce unnecessary energy loss. At the same time, optimizing the digestion process, selecting the right raw materials, adding auxiliary materials, optimizing the biogas collection system, recycling waste heat, biofilm reactor technology, and gas purification technology are also hot topics of current attention [1][2][3][4] .…”

“…As a byproduct of agricultural production, cow dung is also a huge biomass resource. However, its energy value is diminished because of the low levels of organic matter and the high concentrations of ammonia [3] . Improper disposal of a large number of agricultural wastes will produce a plethora of gaseous pollutants, including CO 2 , CO, NO x , particulate matter and harmful organic waste gas, which will cause harm to the rural environment [4] .…”