| By blending Class A biosolids with organic and inorganic materials, thirteen unique soil amendments were created with a goal of developing a product able to access a wider market than unblended Class A biosolids. A set of criteria were developed to assess if the developed blends could be successful general-purpose soil amendments used in a wide range of applications. These criteria included public acceptability of product odor and appearance, efficacy in improving plant growth, and ability to meet existing industry specifications for soil amendments. Several blends met all the criteria established for a successful soil amendment product.;The final properties of the blends depended on the initial properties and mixing ratios of the feedstocks and biosolids as well as biological and chemical processes blends underwent during a month long curing period. Certain properties were found to affect plant growth and odor. Blends with rates of CO2 flux from microbial respiration higher than 8 mg CO2-C g OM-1 day-1 or with a pH above 10 were both malodorous and performed poorly in plant growth trials. The five blends which performed best in the plant growth trials had C:N ratios within the range of 10:1-25:1, blends with electrical conductivity (EC5) greater than 6 dS m-1 performed poorly in plant growth trials and there appeared to be an ideal range for NH4+ levels, above and below which plant growth was reduced. |
