Ping Ai

Enhancing ethanol production from thermophilic and mesophilic solid digestate using ozone combined with aqueous ammonia pretreatment

Pretreatment with ozone combined with aqueous ammonia was used to recover residual organic carbon from recalcitrant solid digestate for ethanol production after anaerobic digestion (AD) of rice straw. Methane yield of AD at mesophilic and thermophilic conditions, and ethanol production of solid digestate were investigated. The results showed that the methane yield at thermophilic temperature was 72.2% higher than that at mesophilic temperature under the same conditions of 24days and 17% solid concentration. And also the ethanol production efficiency of solid digestate after thermophilic process was 24.3% higher than that of solid digestate after mesophilic process. In this study, the optimal conditions for integrated methane and ethanol processes were determined as 55°C, 17% solid concentration and 24days. 58.6% of glucose conversion, 142.8g/kg of methane yield and 65.2g/kg of ethanol yield were achieved, and the highest net energy balance was calculated as 6416kJ/kg.

The studies on the methane production with solid state fermentation by mixed the rice straw and swine manures

In this study, an anaerobic dry fermentation system was designed and erected to validate the feasibility and test the performance of dry fermentation by using the mixtures of rice straw and fresh pig manures under the near middle temperature. And during the course of fermentation the leachate was refluxed from the leachate tank to the fermentation tank in order to increase the performance of mass transfer. Some key parameters such as pH value, VFA value, start-up time, gas production and CH4 content were used to reflect the fermentation performance. Experimental results show that after 6 days CH4 content in biogas can be above than 45%, which means that the anaerobic dry fermentation is started up. In addition, the total amount of biogas produced is about 16.55 m3 from 6-day to 22-day, and the maximum volume gas production rate can be about 1.2 m3 biogas/(d·m3 fermentation tank). Furthermore the CH4 content in the biogas after the start-up time can be maintained at about 50%∼70%. These useful results imply that the anaerobic dry fermentation using rice straw and fresh pig manures is viable. On the other side, the germinating index (GI) for cabbage was also experimented to test whether or not the leachate and the fermentation residues can be used to act as fertilizer. Results show that the GI is higher than 70% after 25 days anaerobic fermentation which suggests that these residues can be adopted to act as fertilizer.

Biorefining of rice straw by sequential fermentation and anaerobic digestion for bioethanol and/or biomethane production: Comparison of structural properties and energy output

Three routes; namely R1 representing direct anaerobic digestion (AD), R2 representing enzymatic hydrolysis followed by fermentation, distillation, then AD, and R3 representing AD of fermentation broth without distillation; of alkali pretreated rice straw were investigated. Results showed that sequential fermentation and AD effectively enhanced fibers degradation with significant changes in the composition. Fermentation through R2 resulted in ethanol yield of 87.4 g kg-1 dry straw. Maximum biogas yields of 286.9, 233.3 and 372.4 L kg-1 VS were recorded by AD for R1, R2 and R3 after reaching the steady state at 36, 24 and 33 days, respectively. However, biogas produced through R3 showed the highest significant biomethane content (79.3%) which represented 15 and 8% higher than that of R1 and R2, respectively. Therefore, the highest bioenergy output and energy conversion efficiency of 10.58 GJ ton-1 and 75.6%, respectively, were obtained through R3 demonstrating the positive effect of fermentation prior to AD.

The Assessment of Three Straw Utilization Project of Rural Energy

As a large agricultural country, China ranks first in the world of the output of crop residues. However, due to the decreasing requirement of rural living energy usage for straw, the surplus of straw is extremely severely in rural area. Recently, the central government encouraged greatly the straw utilization, and the large-scale straw utilization is the main content of the rural energy now. As for three modes of large-scale straw utilization in rural energy fields such as: straw gasification, straw biogas and straw molding fuel (solidification/carbonization), these modes are planned to be compared, analyzed and evaluated in this paper to capably provide selection reference for large-scale utilization of straw and boost the development of straw resource utilization in rural China.

The Effect of Alkali Pretreatment of Rice Straw for Anaerobic Digestion

The anaerobic digestion is an efficient utilization way of crop residues and alkali pretreatment are often used to enhance the degradation. Alkali pretreatment based on Ca(OH)2 addition of rice straw was studied.The tests of 3 g/l, 9 g/l Ca(OH)2 addition had an significant effect on enhancing solubilization and rapid acidification, the results were 1521.2 gCOD/l and 935 ml biogas yield of 3 g/l Ca(OH)2 addition, 1600.7 gCOD/l and 1200 ml biogas yield of 9 g/l Ca(OH)2 addition , compared to 405.5 gCOD/l and 1162 ml of control( 0 g/l Ca(OH)2 addition) . The results also showed that tests of 15 g/l , 21 g/l of Ca(OH)2 addition were entirely inhibited to biogas yield. The result of the present work implied that although alkali pretreatment to rice straw can significantly enhance solubilization, the inhibition to methane yield was liable to occur.