生命科学学院知识库

我国是人口众多的农业国家， 生物质能在我国的能源结构中占有相当重要的地位，生物质能虽然不是主要的商品能源，在农村仍是主要的能源之一。长期以来，大多生物质能的利用以直接燃烧为主，不仅热效率低下，而且伴随着大量的烟尘和余灰的排放，成为阻碍农村经济发展和社会进步的重要因素之一。农村户用生物质能清洁利用技术的研究与推广应用，可有效提高资源利用效率，减少和避免污染物的产生，保护和改善环境，保障人体健康，促进经济与社会的可持续发展。

本文在系统分析我国生物质能利用特点和半干旱区农业生产基本特征的基础上，提出了半干旱区户用生物质能清洁利用生态工程的设计原则和设计内容，基于将其确定为一个完整的生态系统， 从生态系统生态学的角度对该系统的能量流动状况进行了研究。本文根据国际通用的减排量计算方法，对中国农村户用沼气替代传统生物质能和煤炭所产生的 CO2 和 SO2 的减排量进行了计算和分析。依照生态工程评价原则建立了半干旱区户用生物质能清洁利用生态工程评价指标体系。主要研究结果如下：
1、对半干旱区户用生物质能清洁利用生态工程的设计原理、设计标准、基本结构和特征形成了科学认识。2、应用系统能量学和热力学方法，对半干旱区户用生物质能清洁利用生态工程的典型案例，进行了能量转化试验研究。通过系统模拟技术建立了构成该模式的3个子系统的能量平衡方程。结果表明，日光温室种植子系统、畜圈饲养子系统和沼气池厌氧发酵子系统能量输出分别占总能量输出的21%，47%和32%，能量转化率分别达到1.37%、64%和84%，辅助能转化率为 65%。该系统能量转化机制合理，符合生态系统的基本规律，是适合在中国半干旱地区推广的生态工程。3、农村户用沼气工程是中国生物质能清洁利用的重点建设项目，可为农村居民提供清洁的生活用能，该工程的建设能减轻农村环境污染，有助于部分缓解全球变暖的趋势。利用国际通用的减排量计算方法，对中国农村户用沼气建设替代传统生物质能和煤炭等所产生的 CO2 和 SO2 减排量进行了计算和分析。对现阶段我国农村户用沼气建设中 CO2 和 SO2 的减排效应作了计算和分析，预测了2010-2050 年我国农村户用沼气建设的 CO2 和 SO2 的减排效益。结果表明，1996-2003 年间若用每年所产的全部沼气分别代替秸秆、薪柴或煤炭，替代后CO2的年均减排量为39.76-419.39万t，SO2的年均减排量为2.13-6.20 万t。在2010-2050年的 40 年间，按照农村地区沼气需求及其替代传统生活能源消费的减排效益的常规预测方案，用沼气替代传统生物质能将使 CO2 年排放量减少 187.13-2178.75万t，SO2年排放量将减少7.97-46.90万 t；按照农村地区沼气需求及其替代传统生活能源消费的减排效益的加强预测方案，在2010-2050年的40年间，用沼气替代传统生物质能将使 CO2 年排放量减少 307.77-4592.80 万t，SO2 年排放量将减少 13.11-98.87 万 t。证明农村户用沼气工程的建设可以有效减少 CO2 和 SO2的排放。4、半干旱区户用生物质能清洁利用生态工程综合效益显著。在项目实施区农民纯收入得到增加，农户能够使用以沼气为主的清洁能源，农户传统生物质能源消费比例逐渐下降，可实现节能、增收 、保护环境同步的效益。5、建立了半干旱区户用生物质能清洁利用生态工程评价指标体系。

China is an agricultural country with a large population. Bio-energy is one of important parts of all energy structure in China, especially in rural area, though it is not the main commercial energy. The main use of bio-energy was burning directly for a long time, which was not only low hot efficient but also release a large amount of dusts and ashes, and this has been one of important factors retarded the development of economy and social progress in rural area. The researches on household scaled bio-energy cleaning utilization and the extension of the related techniques can improve resource efficiently, reduce and avoid polluted materials, protect and improve environment quality, and keep people health. Therefore it can improve the sustainable development of economy and society.
This paper analyses characteristics of bio-energy utilization and agricultural system in arid area of China, and puts forward ecological engineering design principle and design context of rural household scaled bio-energy cleaning utilization in arid area. Energy mechanism of transition and energy flowing of this ecological engineering were studied based on taking this system as a whole system in ecology view. According to the international universal calculating methods, the release of CO2 and SO2 were calculated and related analyses were made to biogas as a substitute for traditional bio-energy and coal. Ecological engineering evaluation system of rural area household bio-energy cleaning utilization in arid area was established according to ecological engineering index evaluation principle. The main results contents were summarized as follows:
1. Scientifically recognized rural household bio-energy cleaning utilization ecological engineering in semi-arid area, including the design principle, design standard, basic structure contents and the main characters of this system.
2. Methodologies of system energetics and thermodynamics were applied to study the typical case of the energy transition mechanism in this ecological engineering system. This rural ecological engineering system consisted of 3 subsystems, of which were greenhouse, livestock barn and biogas digester. Energy balance equations for each of the subsystem were established according to systemic simulation technique. The results showed that the percentages of energy output from subsystems of greenhouse, livestock barn and biogas digester were 21%, 47% and 32%, and the rates of energy transition were 1.37%, 64% and 84% respectively. The auxiliary energy transition rate was up to 65%. The mechanism of energy transition in the ecological engineering was reasonable and should be extended in semi-arid rural area of China.

3. Rural household biogas construction is a key construction program to current bio-energy cleaning utilization engineering in China. As daily-consumed energy for livelihood, biogas can substitute traditional biomass energy and provide clean energy for the rural residents, which can reduce the discharge of noxious gas, such as CO2 and SO2, and therefore partly moderate the tendency of the global warming. The quantity of emission reduction caused by household biogas construction’s substitution from 1996 to 2003 was analyzed according to international commonly used calculation method of emission reduction. The result showed that the use of biogas can reduce the discharge of CO2 397 600 to 4 193 900 ton and SO2 21 300 to 62 000 ton. The emission reduction of CO2 and SO2 brought by the development of household biogas industry from 2010 to 2050 is forecasted. According to the regular scenario of the energy demand forecast of rural China, the use of biogas can reduce the discharge of CO2 1 871 300 to 21 787 500 ton and SO2 79 700 to 469 000 ton from 2010 to 2050. As the strengthening scenario the quantity reduce discharge of CO2 30 777 000 to 45 928 000 ton and SO2 131 100 to 988 700 ton from 2010 to 2050.The rural household biogas construction of China is effective measures to save energy, improve the efficiency of energy utilization, decrease the discharge of air pollution and lower the incidence rate of disease caused by poisonous gas.
4. The comprehensive effects on rural household bio-energy cleaning utilization ecological engineering in arid area were significant. Farmers’ income was highly improved in the areas where rural household bio-energy cleaning utilization ecological engineering was used. Biogas can be used as main resource in rural areas,which decreased the percentage of rural household traditional bio-energy utilization, therefore it saves energy and resource, improves farmers’ income and protects rural environment as well.
5. Established the evaluation index system for rural household bio-energy cleaning utilization ecological engineering in arid area.