城市污泥不同处理处置工艺路线碳排放比较

随着碳中和目标的提出,城市污泥高效资源化利用成为研究热点,为从碳排放角度对污泥处理处置技术路线进行科学比较,对4种典型污泥处理处置路线进行碳核算.基于联合国政府间气候变化专门委员会(IPCC)提供的方法,结合我国污泥特性,以每t干污泥(DS)为核算对象,核算边界从污泥浓缩开始,到最终作为产品输出或能量回收为止,分为直接排放、间接排放和碳补偿这3种类型计算总碳排放量.结果表明R4路线(重力浓缩+热水解+厌氧消化+板框压滤脱水+运输+土地利用)总碳排放量(以CO₂/DS计,下同)为99.41 kg·t^-1,是最为低碳的污泥处理处置工艺路线,若避免其厌氧消化CH₄逸散排放,该路线现阶段已能够实现碳中和.对碳排放量较大单元,如热干化1 049.24 kg·t^-1,深度脱水960.99 kg·t^-1,卫生填埋786.24 kg·t^-1,焚烧635.52 kg·t^-1,好氧堆肥614.17 kg·t^-1,热水解544.67 ...

Comparison of Carbon Emissions in Different Treatment and Disposal Process Routes of Municipal Sludge

With the introduction of the goal of carbon neutrality, the efficient resource recycling of municipal sludge has been given increasing attention. In order to scientifically evaluate the routes of sludge treatment and disposal from the perspective of carbon emissions, four typical routes were chosen for accounting the carbon emissions per ton for dry sludge (DS). Based on the Intergovernmental Panel on Climate Change (IPCC), combined with Chinese sludge characteristics, carbon emissions were divided into three types:the direct emissions, indirect emissions, and carbon offsets, and accounting boundaries were initiated at sludge thickening and ended at products or energies. The results showed that the total carbon emission of R4 (gravity thickening+thermal hydrolysis+anaerobic digestion+plate and frame filter pressing+transportation+land utilization) was 99.41 kg·t^-1(calculated as CO₂/DS, same below), which was the route with lowest carbon emissions. If the fugitive emission of CH₄ from anaerobic digestion was avoided, the route (R4) could achieve carbon neutrality at this stage. Process units with larger carbon emissions should focus on optimization to reduce the carbon emissions, such as through thermal drying (1049.24 kg·t^-1), deep dewatering (960.99 kg·t^-1), sanitary landfill (786.24 kg·t^-1), incineration (635.52 kg·t^-1), aerobic composting (614.17 kg·t^-1), and thermal hydrolysis (544.67 kg·t^-1). The main carbon offsets were the incineration power generation (-1440.29 kg·t^-1), CH₄ collection of anaerobic digestion (-435.06 kg·t^-1), land utilization (-415.83 kg·t^-1), and building materials utilization (-169.75 kg·t^-1). In summary, "anaerobic digestion and land utilization" has a great potential for carbon offsets, which should be advocated for as the widely used treatment.