不同温度下氢氧化钠预处理对玉米秸秆甲烷产量的影响
宋籽霖1,2，孙雪文3，杨改河4，闫志英1,2，袁月祥1,2，李东1,2，李香真1,2，刘晓风1,2
【摘 要】摘要：利用农作物秸秆进行厌氧发酵生产沼气是解决我国农村能源紧张的重要途径，然而秸秆中难以降解的木质纤维结构导致在发酵过程中甲烷转化率较低。利用自行设计的可控性恒温发酵装置，以玉米秸秆为发酵原料，分析了在不同温度条件下氢氧化钠（NaOH）预处理对秸秆木质纤维结构以及厌氧发酵产气效率的影响。结果表明，NaOH预处理能够显著降低玉米秸秆的木质纤维素含量，与未预处理的秸秆相比，经NaOH处理后的秸秆纤维素含量降低了24.4%～33.2%，半纤维素含量降低了14.2%～52.4%，木质素含量降低了9.3%～29.3%。在6%、8%和10%浓度中，经8%NaOH处理的秸秆在55℃下的甲烷产量最高，达到188.7 ml CH4·(g VS)?1，较未处理的增加了84.2%，因此可作为提高秸秆厌氧发酵产气效率的预处理方法。 【期刊名称】化工学报 【年(卷),期】2014(000)005 【总页数】7
【关键词】甲烷产量；厌氧发酵；NaOH；预处理；玉米秸秆
Introduction
Depletion of fossil energy and continuous increase in greenhouse gas emission in the atmosphere have attracted scientists’ interest to develop renewable and sustainable energy alternative to fossil energy[1-2]. Biomass is considered as a valuable renewable energy
because it can be converted to various available forms of energy, such as heat, steam, electricity and biofuels. As the largest agriculture country in the world, China has abundant biomass resource, including crop straw, animal manure and organic wastes.
An estimate shows that approximately 800 million tons of various crop residues are produced in China per year, of which corn and wheat straw account for 216 million and 135 million tons, respectively[3]. Apart from part of crop straw utilized as animal feed, most straw is dumped into field or burnt in open environment. Methane yield from crop straw through anaerobic digestion (AD) is growing worldwide and is considered as the important energy because it not only meets the life needs for energy, but reduces methane emission[4-5]. However, the efficiency of this technology was limited due to the lignocellulosic structure (cellulose, hemicelluloses, and lignin) resistant to anaerobic microorganism for converting into methane[6]. Pretreatment
before
digestion,
including
solubilization
and
biodegradation of the hemicellulosic and lignin components of the substrates can increase methane yield by overcoming hydrolysis limitations[7]. The pretreatment methods mainly include physical method[8], chemical method[9]and biological method[10]. Sodium hydroxide (NaOH) and thermal treatments are the two common methods that have been used for pretreatment of lignocellulosic
biomass[11-13]. In particular, the treatment at high concentration of NaOH (at 6%—10%) can dissolve the lignin and/or cellulose (depending on temperature) of lignocelluloses and efficiently improve the structure of these materials. These methods have been carried out on different lignocellulosic materials like rice straw[2], cattle manure with corn stover[14], hardwoods[15], softwoods and pulp and paper sludge[16]to improve digestibility. However, these studies were mostly focused on single (NaOH) treatment or thermal treatment during the AD process, no available information is on the combination of these two methods. In the present study, the effects of NaOH pretreatment of corn straw at different temperatures on the lignocellulosic structure changes and methane yield by AD were investigated. The objective was to determine the optimal conditions of NaOH pretreatment for improving anaerobic digestibility of corn straw.
1 Material and methods
1.1 Material collection
Corn straw was obtained from local village near Northwest A&F University (Yangling, Shaanxi, China). Prior to use, straws were air dried and cut into 20 mm to 30 mm in length by using a grinder. The composition of corn straw is shown in Table 1. 1.2 Pretreatment process
NaOH was used for pretreatment. Firstly, 6%, 8%, and 10% (dry mass of
不同温度下氢氧化钠预处理对玉米秸秆甲烷产量的影响
