Resourclization Of Corn Stover Using Electrochemical Microbial Anaerobic Systems

Electrochemical microbial anaerobic system (EMAS) make it possible to take corn stalks as potential recourse, yeilding diversiform production such as CH₄ and H₂. What is more, the predominances, such as high efficiency, low utilized cost and high energy transform ratio, of EMAS are obvious. Building up and domesticating high efficiency microbial fuel cell (MFC) system was considered to be the necessary process and key technic in approching the EMAS and comprehensive utilization of corn stalks.Raw corn stalks were added directly into microbial fuel cell (MFC) system after crushed . In order to obtain higher maximum power density, different types of anode material and configurations of air cathode MFCs (carbon brush anode bottle reactor and carbon brush anode cubic reactor) were investigated in MFC system. Raw corn stalks could be degraded by cellulose bacteria community H C , and be consumed in single chamber,air cathode MFC with 50mM phosphate buffer system . In the carbon brush anode and air cathode bottle reactors, the maximum power density was 651±10mW/m² using glucose (1g/L) as substrate. After adding H C and raw corn stover into this systerm at the same time, the maximum power density of corn stover reduced to 599±15 mW/m². In the carbon brush anode and air cathode cubic reactors, the maximum power density of glucose (1 g/L) was 769±3 mW/m². When the corn stover was used as substance, the maximum power density obtained was 444±36 mW/m², although the voltage generation was not very stable due to the problem of matter transfer between anode and cathode. The result indicated that changing anode material and configurations of reactor could greatly enhance the maximum power density. When dissolvable organisms were used as substrate, the cubic reactor obtained higher max power density. However, the bottle reactor has advantages in comparison with cubic reactor using raw corn stalks as substrate , due to larger volume and better mass transfer condition.Raw corn stalks could be degraded by cellulose degradation beacteria community H C without MFC system. Degradation solution of corn stalks , after 1¹4 days of degradation by H C ,were investigate about their possiblity to be used as substrate in MFc system . During the period of degradation, the COD of corn stalks degradation solution were observed to increase fluctuantly. The peak of COD data (2022 mg/L) was observed in the 12th day of degradation. During the degradation, three distinct areas of high degradation rates, respectively, observed in the vicinity of 3, 7 and 12 days. Compared with glucose, the maximum power output , using degradation solution of corn stalks as substrate, were generally low. Howere, when the degradation solution of straw collected at 12th and 13th day were used as substrate, higher maximum power density (respectively 820.5±31.6 mW/m² and 851.1±13.5 mW/m²) were observed to obtain than glucose (802.5±19.4 mW/m²). The electrode potential analyse indicated that the corn stalks degradation solution could keep the anode potential relatively lower than that of glucose, which were thought to be propitious to the grow and power generation of anode bacteria community. However, the cathode protential were observed to decrease, which was the main cause that result in the maximum power output of degradation solution of corn stalks generally lower than that of glucose. It was approved in the experiment that power generation from degradation solution of corn stalks is doable. Compared with glucose, higher power density output could be obtained, using degradation solution of corn stalks through a proper period of degradation.In order to creat condition for farther study of using raw corn stalks and degradation solution in EMAS system as a potential resource, a application oriented pilot MFC system (250L, brush anode and air cathode ) was designed and started up. By far ,domestic sewage was used as substrate. After 250h's domestication, stable output current (0.14⁰.18A) was generated. Measured by polarization curves, after adding 40% corn stalks degradation solution into the system, the reaction ohmic resistance was only 2.5±0.2Ω, maximum power output was 58 mW (0.93W/m³). Sucessful design and strat up of the pilot MFC system, make the utilization of raw stalks, basing on the technic of microbial fuel cell, more meaningful and closer to the practical application.