The use of sewage has two key points in favour. First it involves recycling waste and this helps to reduce the carbon footprint. Secondly, the sewage contains a high level of phosphorus, which is a key growth factor for many plants. Plants must have phosphorus for normal growth and maturity. Phosphorus plays a role in photosynthesis, respiration, energy storage and transfer, cell division, cell enlargement and several other processes in plants.
The common source of phosphorus is from non-renewable phosphate rocks. Due to this being a infinite and expensive resource there is a driver to find easy ways to recycle phosphorus. It is for this reason scientists have looked towards the use of sewage sludge.
Researchers from the University of Antananarivo (Madagascar) have developed a phosphorus radiotracer technique that measures the availability of phosphorus for plants in thermally conditioned sewage sludge.
This technique was used to examine ryegrass. The grass was grown in pots that contained either no fertilizer, thermally conditioned sewage sludge, or a commercial phosphate-based fertilizer. The plants without fertilizer grew poorly and those with fertilizer grew well and showed larger root biomass. The thermally conditioned sewage sludge gave similar results to the commercial fertilizer.
In a research note, the lead scientist Dr. Andry Andriamananjara explains that the thermally conditioned sewage sludge has “shown to have a higher agronomic effectiveness in comparison with commercial fertilizer.”
He also reiterated the advantages as: “sewage sludge is a non-limited continuously available and sustainable fertilizer source.”
The use of sewage as a fertilizer is published in the journal Frontiers in Nutrition. The research study is titled “Drivers of Plant-Availability of Phosphorus from Thermally Conditioned Sewage Sludge as Assessed by Isotopic Labeling.”
