大型秸秆沼气集中供气工程温室气体减排估算

发展秸秆沼气工程可有效地减少农业温室气体排放,科学核算温室气体减排量为管理和监督温室气体排放状况提供数据支撑。该文以河北省沧州市耿官屯大型秸秆沼气集中供气工程为研究对象,参考和借鉴了自愿减排项目方法学、CDM方法学,构建了大型秸秆沼气集中供气工程温室气体减排计量方法,包括项目边界、基准线排放量、项目排放量、泄漏量、减排量5个方面,计算了2014年耿官屯大型秸秆沼气集中供气工程温室气体减排量。研究结果表明:项目基准排放量包括秸秆处理产生的温室气体排放、未建秸秆沼气工程情况下农村居民生活用能及农田施用化肥生产耗能产生的温室气体排放。项目排放量包括秸秆与沼肥运输过程耗能排放、工程运行过程耗能排放及沼气处理温室气体排放,项目泄漏量即沼气生产、储存、管网供气和利用过程中产生的因物理泄漏所造成的排放。2014年耿官屯大型秸秆沼气集中供气工程基准线CO2排放量为5 776.15 t,项目排放量为57.53 t,泄漏量为136.59 t,减排量为5 582.03 t,约相当于2 100 t标准煤CO2排放量,每消耗1 t(干质量)秸秆可净减排3.56 t,每利用1 m3沼气可净减排11.50 kg。同时,在工程设计、管道设计、工程管理、工艺技术改良升级等方面提出了提升大型秸秆沼气工程温室气体减排能力的策略。

Greenhouse gas emission mitigation calculation of large scale straw biogas centralized supply project

Abstract: The large straw biogas project is an important way of new energy utilization of straw resource in China. It has great meaning to facilitate the construction of a resource-saving and environment-friendly society and mitigation of climate change. The methods of literature research, fixed point monitoring and quantitative analysis were adopted. Taking the straw biogas project in Gengguan Village of Cangzhou City in Hebei Province of China as an example, this paper establishes a methodology of greenhouse gas emission reduction for large scale straw biogas project. The greenhouse gas emission reduction measures include project boundary, calculation of baseline emissions, project emissions calculation, leakage calculation, emission reduction and project monitoring. Calculation of baseline emissions refer to the greenhouse gas emission by straw stalk treating, rural resident daily used energy, and fertilizer production in farmland under no large straw biogas project. Project emissions calculation refers to the emissions produced by engineering transportation, power consumption, fossil fuel consumption and extra biogas torch combustion. We calculate the greenhouse gas emission reduction of the straw biogas project in 2014. The results show that the baseline CO2 emissions are 5 776.15 t, the project CO2 emissions are 57.53 t, the leakage of CO2 is 136.59 t and the CO2 emission reduction is 5 582.03 t, which is approximately equal to CO2 emissions by 2 100 t standard coal combustion. As required in NY/T 2142-2012 Specification for Process Design of Straw Biogas Engineering, the design working life of straw biogas engineering is no less than 25 a, the Gengguan Village straw biogas centralized gas supply project can at least achieve CO2 emissions of 139 600 t. For every 1 t straw (dry weight) consumed, a net reduction of 3.56 t CO2 emission can be got, and for every 1 m3 methane used, 11.50 kg CO2 emission can be reduced. Through the construction of greenhouse gas emission reduction measurement method of large scale straw biogas centralized gas supply projects, it is helpful to understand the emission reduction utility of large scale straw biogas centralized gas supply projects scientifically, analyze the main greenhouse gas emission sources during the project operation quantitatively, and further enhance the straw emission reduction capacity of biogas centralized gas supply projects. The order of the contribution of greenhouse gas emission is: Leakage > engineering operating power consumption emission > energy consumption emission of coal combustion in engineering operation > engineering transport activity emission. Leakage accounts for 70.36% of the total emissions, engineering operating power consumption emission accounts for 22.41%, energy consumption of coal combustion in engineering operation accounts for 4.71%, and engineering transport accounts for 2.52%. To reduce the operation and leakage emissions, the straw biogas projects should be located in the more concentrated areas of farmers, choose the material with corrosion resistance, good pressure resistance and strong environmental suitability, and change the flange connection and threaded connection to welding. In the meantime, we should strengthen the daily inspection, maintenance and management, upgrade the straw pretreatment (crushing) process technology, promote and use the solar heating, biomass furnace heating, biogas warming and other clean energy warming technology and greenhouse thermal insulation technology measures, and layout the straw storage sites and biogas fertilizer treatment center reasonably to reduce the energy consumption in the transportation. In view of the shortcomings of this study in the parameter selection, regional application and other aspects, we will strengthen the studies on relevant parameters and different regional case further.