Application of amendments in composting:A review

Amendments are important assistant materials in the composting process. In order to complete the composting process efficiently, the materials for composting should meet some physical and chemical characteristics such as w(C)/w(N) ratio (carbon nitrogen ratio), moisture content, free air space, etc., under which conditions aerobic microorganisms can thrive. According to amendments’ chemical property, they can be divided into two types: active amendments which can be biodegradable in the composting and inert amendments which can not be. Active amendments mainly improve the chemical characteristic of the materials, while inert amendments mainly improve the physical structure of the composting matrix and the quality of the compost product. This paper reviews the function of many amendments in literatures, which includes six aspects: adjusting the w(C)/w(N) ratio of the materials, regulating moisture content, modulating the free air space, reducing the odors in the process, improving the nutrient quality of the product and decreasing the effectiveness of heavy metals. In recent literatures, researchers focus on whether the composting can be completed successfully after adding amendments. However, there are some other aspects about amendment should be pay more attention, such as: the development of compound amendments, the mechanism in which amendments affect the composting process, the application of amendments in composting engineering.