Class A biosolids is a term used primarily in the US to describe biosolids that are the end product of municipal wastewater treatment plant residuals that have been further processed to achieve a greater level of pathogen reduction. Equivalent materials in Canada are land applied as a fertilizer with a Canadian Food Inspection Agency label. Class B biosolids continue to be applied to land using a NASM Plan.
There is a demand for Class A biosolids in the agricultural community as an alternative to traditional land application programs since there is less restriction in end use. Class A technologies include thermal drying, composting, pasteurization and lime stabilization, and can produce a pellet, solid or liquid material with pH adjusting properties.
Some benefits of Class A biosolids include:
- Reduction in volume, weight and storage requirements
- Pathogen and vector attraction reduction
- Reduction in odour
- Reduced transportation cost
- Opportunity to sell the material as a fertilizer
- Rehabilitation of mine and forestry projects
- Use on publicly accessible areas (i.e. parks, golf courses and gardens)