[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.