冬季污泥堆肥过程温室气体排放特征

污泥堆肥处理是一种简便高效的污泥稳定化技术,但堆肥过程产生的温室气体也引起了国内外的广泛关注,我国关于污泥堆肥,特别是低温环境下的堆肥温室气体排放特征研究和基础数据还很缺乏.本实验采用城市脱水污泥,考察低温环境条件下不同调理剂混合污泥堆肥过程中温室气体的排放特征.结果表明,低温环境条件下污泥堆肥能够顺利进行,但高温期持续时间相对较短而腐熟期温度降低过快.木屑处理的总氮损失低于秸秆处理,然而温室气体总排放当量却高于秸秆处理,木屑和秸秆处理总的CO2排放当量(以干污泥计)分别为169.45 kg·t~(-1)、133.13 kg·t~(-1).木屑与秸秆CH_4累积排放量(以干污泥计)分别为0.648 kg·t~(-1)、0.689 kg·t~(-1),N_2O累积排放量(以干污泥计)分别为0.486 kg·t~(-1)、0.365 kg·t~(-1).CH_4的排放75%以上集中在堆肥前2周,而N_2O则90%以上出现在后腐熟期.整体而言,冬季堆肥高温期持续时间相对较短而腐熟期温度低,出现CH_4排放量相对较低而N_2O较高的现象,CH_4排放量均低于IPCC推荐值,N_2O则均高于IPCC推荐值.因此针对低温环境堆肥工艺,温室气体的减排应重点关注堆肥后期N_2O排放的降低策略.

Emissions Characteristics of Greenhouse Gas from Sewage Sludge Composting Process in Winter

Sludge composting is an efficient way to realize the reclamation of waste sludge, while the Green House Gas (GHG) accompanying with it has raised great concern worldwide. However, we do lack the primary data in this area and a great uncertainty of the effect and GHG emission characteristics of sludge composting process in low-temperature environment also exists. This study is aiming to investigate the emission characteristics of GHG from composting in low-temperature environment by applying two different bulking agents to dewatered urban sludge. The results showed that aerobic composting could go smoothly even in an environment with lower temperature, yet the maturity was low due to a sharp drop of pile temperature at the stage of maturing. Sawdust treatment could reduce the total nitrogen loss compared with cornstalk treatment, while its GHG emission equivalence was higher (169.45 and 133.13 kg·t^-1 dry sludge, respectively). The accumulative CH₄ emissions of sawdust and cornstalk were 0.648 and 0.689 kg·t^-1 dry sludge, respectively, of which over 75% was from the first two weeks; total N₂O emissions of sawdust and cornstalk were 0.486 and 0.365 kg·t^-1 dry sludge, of which more than 90% came from the decomposting process. On the whole, because of the relatively short duration of high temperature as well as the low temperature during mature stage, the process had an especially low emission of CH₄ but a relatively high discharge of N₂O. For composting in low-temperature environment, necessary measures should be taken to control N₂O emission in the late period in order to realize GHG reduction.