Search

Effect of adding bamboo biochar into the compost at different dosages on greenhouse gas emissions was investigated by analyzing the dynamic characteristics of the process of municipal sludge composting with four different composts (S1:adding 2.5% bamboo biochar, S2:adding 5% bamboo biochar, S3:adding 10% bamboo biochar, CK:without bamboo biochar). The results showed that CH 4 emissions mainly occurred during the heating period and the beginning of the altithermal period, accounting for 99.01%-99.81% of the total emissions. When the added bamboo biochar is less than 5%, CH 4 emissions decrease with the increase in the amount of bamboo biochar. If it is more than 5%, CH 4 emissions will clearly increase. CO 2 emissions mainly occurred during the heating period and the altithermal period, accounting for 75.65%-86.58% of the total emissions. Adding bamboo biochar can reduce 3.37%-13.48% of the CO 2 emissions but there is no significant difference between the treatments ( P >0.05). N 2 O emissions mainly occurred during the heating period and the rotten period. Adding bamboo biochar can reduce the emissions of N 2 O; the more the amount of bamboo biochar, the less N 2 O emissions ( P <0.05). The emission factors of CK, S1, S2, and S3 were 44.10, 37.57, 35.10, and 35.44 kg·t -1 of dry sludge, respectively. S1, S2, and S3 showed 14.81%-20.41% reduction in greenhouse gas emissions owing to the addition of bamboo biochar, indicating that bamboo biochar can reduce the carbon emissions in the process of sludge composting.

Effect of application of sewage sludge compost on the emission of greenhouse gas from soil was investigated by analyzing the dynamic characteristics and emission factor of CO 2 , CH 4 and N 2 O in soil after spiking two different composts (A:compost with biochar, B:compost without biochar) with varying fertilizing amount into soil. The results indicated that emissions of CO 2 and CH 4 mainly occurred in the plant growth period with low fertilizer amount of biomass charcoal compost reducing CO 2 emissions, and high application content increasing CO 2 emissions. CH 4 emission fluxes showed negative values, indicating that soil could adsorb CH 4 , and the adsorbing amount for control was significantly higher than those for other treatments ( P <0.01). The absorbing amount in treatment A increased with the fertilizing amount ( P <0.05). N 2 O emissions mainly occurred at the germination and seedling stages, and emission fluxes increased with the fertilizing amount ( P <0.01). N 2 O was considered as the main generated greenhouse gas during agricultural process with sludge compost, and its emission factor from sludge compost soil was 1.02%-1.90% (A compost) and 1.28%-2.93% (B compost), respectively. Biochar could significantly reduce the carbon emission, as the total greenhouse gas released from soil with biochar compost was 19.49% to 35.56% less than that in soil without biochar, which was more obvious for N 2 O emission reduction (compared with CH 4 mitigation).

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 CH 4 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 N 2 O 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 CH 4 but a relatively high discharge of N 2 O. For composting in low-temperature environment, necessary measures should be taken to control N 2 O emission in the late period in order to realize GHG reduction.