The processing of biosolids from wastewater treatment plants have resulted in the production of affordable organic fertilizer which can be used in agriculture to revitalize nutrient deficient soils. Instead of ending up in landfills, biosolids have given farmers a cheap and environment-friendly source of organic fertilizer.
Through the years, the process of biosolids production has been refined to the point where “exceptional quality” biosolids are now possible. These have high nutrient content designed specifically for facilitating vegetative growth and have high levels of nitrogen.
Nitrogen is key to this growth but only a portion of it is consumed by the plants. This fraction is known as bioavailable nitrogen.
Odiney Alvarez-Campos, a researcher at Virginia Tech, has been studying the optimum levels of nitrogen in biosolids that can be used as organic fertilizers. “We need to know how much nitrogen becomes bioavailable when we add biosolids to the soil. We want to supply enough for healthy crop growth and yields, but not surplus nitrogen.”
Excess levels of nitrogen in organic fertilizers can be harmful to the environment because it can pollute the groundwater and cause an imbalance in aquatic ecosystems that can result in algal blooms. “It’s a balance between supporting plant growth, while not polluting,” added Alvarez-Campos.
Different biosolid products were examined and their bioavailability levels were studied when spread in urban soil. It was discovered that the degraded quality of urban soils plays a role in decreasing the bioavailability of nitrogen.
Urban soils are very compact and have very low organic matter and nutrients as a result of human activities like heavy vehicle traffic and construction. Alvarez-Campos believes that biosolids can restore these soils because of the higher organic matter content of biosolids which can assist with reducing soil compaction. This provides a healthy environment for plant life because it allows the root to grow. It also allows for more water retention which can be retained longer when organic fertilizers from biosolids are applied.
The researchers found that pure biosolids had higher nitrogen bioavailability compared to biosolids that were mixed with organic matter such as woodchips. This is due to the low organic matter and high clay content of urban soil which made the nitrogen less accessible to the plants.
Alvarez-Campos used a modality called the 7-day anaerobic incubation method to get the best estimates of nitrogen availability from biosolids. “It showed the greatest potential to be used as an indicator of the biosolids’ nitrogen availability,” she claimed.
It is expected that the data extracted from this study will be used to better determine application rates of biosolids depending on the degree of soil degradation. They are evaluating the reliability of quick tests to estimate nitrogen availability from biosolids applied to urban soils.
The next step is to expand their study to more areas to size up the variety of soils across the country.
“Recycling biosolids into the soil is one of the most sustainable ways to manage waste,” says Alvarez-Campos. “It returns carbon and nutrients—like nitrogen—to the soil, and helps vegetation grow.”
Clearly, biosolids can do more for the environment rather than ending up in landfills. Studies like these are valuable in unlocking a renewable resource that would lead to zero waste and sustainable vegetations even with poor soil quality.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.