Using biosolids for your garden and landscapes is beneficial for the community and the environment. Since biosolids are locally produced, with its sources coming from domestic waste, using it as organic fertilizers for your garden is directly impacting in a positive way the local community and environment.
There are three types of biosolids that can be used for gardens. Each of this type has different properties and uses. They have been treated and processed with heat to remove the pathogens and other harmful contaminants.
These are considered the type of biosolids with the most nutrients retained. They pathogens are removed through the use of intense heat. It also dries up the biosolids. The temperature used to destroy pathogens is somewhere between 300 degrees and more than 1000 degrees Fahrenheit. Heat drying biosolids not only remove the pathogens, but it does so without ridding the biosolids off the important nutrients garden soil needs. The result is similar to pellets that are contained in organic fertilizers.
The nitrogen content of heat-dried biosolids ranges from 4% to 7%. The phosphorus is at a similar level. Heat-dried biosolids vary in size. Some look like pellets while others may be a bit dusty and are unpleasant to handle. They may have a strong odor when they become wet from rainfall, so test out a small area first if you can handle the smell.
Like heat-dried biosolids, the process of composting kills off pathogens by using high temperatures (even greater than 131 degrees Fahrenheit). Commercial composting methods mix the biosolids with other carbon-rich materials because they do not have enough porosity to supply the oxygen needed by the composting organisms. Among the materials used to mix with the biosolids are wood waste and yard debris. The result is a material that is porous and moist enough for composting.
However, the mixing of biosolids with carbon-rich materials also reduces the concentration of plant nutrients such as nitrogen. Biosolids compost typically only has 1.5% to 2% total nitrogen, 5% to 10% of which are used during the first year. Biosolids compost is better used as a soil amendment rather than fertilizer.
Undiluted biosolids are sticky and they clump readily, which is why they are not convenient to be used in gardens and landscaping projects. In order for these biosolids to be garden-friendly, they have to be blended with other materials that could reduce clumping. These materials are identified as sand, sawdust, and bark. Biosolids blends have less than 1.5% nitrogen and phosphorus because they have been diluted with wood and sand.