C/N比和含固率对牛粪发酵产电性能的影响

为了降低牛粪等农业固体废弃物的污染,并获取新能源,该文以牛粪和小麦秸秆为原料构建了双室型农业固体废弃物发酵产电装置,研究了碳氮比(20、30)和含固率(1%、5%、10%)对牛粪发酵产电和发酵固态剩余物性能的影响,分析了牛粪发酵过程中电压、电流和功率密度的变化规律以及发酵后挥发性脂肪酸(volatile fatty acid,VFA)和p H值的变化。研究结果表明:当含固率为1%,C/N比为20时,产生的电流最大,峰值达到1.12 m A,最大功率密度达464 m W/m2;当含固率为1%,C/N比为30时,产生的电压最大,峰值达到0.80 V,最大功率密度为422 m W/m2;在不同的C/N比和含固率条件下,发酵产电前后VFA浓度和p H值变化明显,与发酵原液相比,VFA浓度增加了2~4倍,p H值下降了0.4~1.2。产电结束后,发酵固态剩余物中有机质、总养分含量和酸碱度符合农业行业《有机肥料》(NY525-2012)标准,可以作为有机肥料或有机肥原料使用,为开发高效、环保的农业固体废弃物资源化利用方式提供参考。

Effects of C/N and solid content of raw materials on electricity generation of cattle manure fermentation

Abstract: In recent years, there are many methods to deal with the cattle manure in China. Those methods include the gathering of biogas with the fermentation technology, producing organic fertilizer with composting technology, and building ecosystems between livestock breeding and plant resources. Although these technologies have been industrialized, methane produced by these technology, needs to be transformed into electrical energy again in use. If organic matter could be transformed into electrical energy directly, the utilization efficiency of solid agricultural resources could be significantly improved, and then enormous economic and social benefits would be produced. Nowadays, the studies of microbial fuel cell (MFC) have gained the concern of many researchers for a long time. In order to reduce the pollution of agricultural solid waste and promote the development of agricultural modernization, an electricity production device with double chambers based on MFC was built and investigated to generate electricity from cow dung and wheat straw. Two ratios of carbon-nitrogen (C/N) (20 and 30) and 3 levels of solid content (1%, 5% and 10%) were selected respectively to study their impacts on the electricity generation efficiency. The variations of many factors were monitored during this process, including voltage, current, power density, volatile fatty acid (VFA) concentration and pH value. The process of electricity production was finished when the voltage reduced to a very low level that was similar to the initial voltage. The results showed that when the solid content was 1%, the electricity generation performance was better than others. When the C/N was 20, the highest voltage, current and power density were 0.57 V, 1.12 mA and 464 mW/m2, respectively. When the C/N was 30, the highest voltage, current and power density were 0.80 V, 0.76 mA and 422 mW/m2, respectively. After the fermentation, VFA concentration and pH value changed obviously under different C/N and solid content. When the C/N was 20, and the solid content was 1%, 5% and 10%, respectively, compared with the initial value, the VFA concentration was increased by 270%, 255% and 313%, respectively, and the pH value was reduced by 0.45, 1.11 and 0.92, respectively; when the C/N was 30, and the solid content was 1%, 5% and 10%, respectively, compared with the initial value, the VFA concentration was increased by 281%, 243% and 395%, respectively, and the pH value was reduced by 0.88, 0.90 and 1.13, respectively. Additionally, the organic matter, total nutrient content and pH value in the solid-state remainder after fermentation met the standards for organic fertilizers of agricultural industry standard (NY525-2012). Therefore, the remainders in solid state after fermentation could be used as organic fertilizers or raw materials of organic fertilizers.