Effect of carbon resources conditioner on composting process and carbon and nitrogen loss during composting of cucumber stalk

Abstract: In China, vegetable growing area and production has been increased rapidly in order to satisfy the demand for vegetable and benefit, which must be accompanied with more and more vegetable waste hard to be treated nowadays. Because of no harmless and circle treatment technology for vegetable wastes in vegetable origin, they would become sources of environmental pollution, especially for cucumber, one of the major vegetables in China. In order to successfully produce soil amendment transferred from vegetable wastes, with the characteristics of high moisture, low C/N ratio, and potential pathogens, we try to use aerobic composting technology to treat them, cucumber waste as an example. The study set three treatments, cucumber waste itself as the control (CK), and the other two with the supplementary carbon conditioners, corn stalk (CS) and woody peat (WP), to make the C/N ratio of the mixed material as 25. By analysis the indexes: the emission rates and accumulative emission amounts of CO2 and ammonia produced per kilogram dry matter, material matter loss, organic matter degradation, pH value, EC, and germination rate index (GI) et al, the effects caused by different carbon conditioners were certified, in order to improve the composting maturity process, and to reduce the losses of carbon and nitrogen in the forms of CO2 and ammonia, so that to reduce greenhouse gas emissions at the same time. The results showed that utilization of additional carbon conditioners (corn stalk and woody peat) during the cucumber waste composting, could decrease the material matter loss in the mixed material, from 59.25% in CK to 54.35% (CS) and 50.75% (WP); accelerate the composting maturity process, one month was enough to get maturity; and corn stalk had better improve effect than woody peat as a carbon conditioner. However, addition of corn stalk increased the organic matter degradation percent (31.27%), CO2 emission rate and the cumulative emission amount (100 g·kg?1), while utilization of woody peat reduced the organic matter degradation percent (17.96%) and total emission amount (77 g·kg?1) when compared with CK (26.55% and 93.52 g/kg). The two carbon conditioners (corn stalk and woody peat) can help to control the ammonia cumulative emission amount, from 7.68 g/kg in CK to 6.52 g/kg in WP and 6.51 g/kg in CS, reduced by more than 15 %. And the work time and mechanism by the carbon conditioners were different. Besides, the two conditioner could help to improve the pH value and EC of the compost product, which would decrease the limitation of the product utilization in agriculture, especially woody peat in WP. Incorporating the composting maturity process, CO2 and ammonia emission rates and cumulative amounts during cucumber waste composting, woody peat had better performance than corn stalk when used as carbon conditioner. While considering the characteristics of corn stalk and woody peat, the improvement effect for maturity process and carbon and nitrogen loss controlling must be more significant if they could be used at the same time, but the performance need to be certify by experiment in the next step.