Human urine is a significant source of nutrients for plants, but digesting it with current sanitation methods can be difficult. Drying diverted urine can be a game-changer in terms of maximizing its benefits. Prithvi Simha, a postdoctoral researcher in environmental engineering at the Swedish University of Agricultural Sciences, told about how pee can be separated, collected, and treated to create fertilizer pellets. In February 2022, Simha published a report on the subject in Source magazine.
Benefits of Dry Urine:
Prithvi Simha says, “Potassium, nitrogen, and phosphorus are abundant in urine. When we flush, pee travels through sewer pipes to treatment plants, where it is diluted by flush water. This makes the process of removing nitrogen from urine, which can be utilized to boost soil fertility, more difficult. Urine can be treated at the source by collecting and drying it separately.”
“We have manufactured dried food and other materials for a long time, therefore the drying technique is not new. We already have the materials necessary to build a urine-drying toilet. The high-end ceramic urine-diverting toilet may be out of reach for the average family. To make urine collection more cost-effective, a simple canister or drum can be placed.”
Stabilization is done to balance the pH level of urine by adding limestone and making it more alkaline. The nutrients are then air blasted at a specific temperature and humidity level to eliminate water and maintain them in a non-volatile state. A concealing trap- 'S' trap or 'C' trap- pipe can be placed to prevent scent or urine from returning to the toilet bowl.
“It has the potential to be a solution for rural India. Multiple urine-handling chambers can be avoided in rural India, and an economically scaled semi-centralized system can be erected, linking several urinals/toilets together, to make the urine-drying system affordable and user-friendly.”
“To treat and dry urine, many urinals or pee-diverting chambers can be connected to a single container/chamber with a dryer. The proceeds from the sale of the finished product (fertilizer) can be put to good use in the system's operation and maintenance,” says Prithvi Simha.
Improves Soil Fertility
The nitrogen and phosphate content of urea promotes soil fertility. By adjusting the nitrogen-phosphorus-potassium ratio, the fertilizer can be turned into pellets. Biochar, for example, adds carbon to the fertilizer, whereas recycling struvite provides phosphates.
The fertilizer has been lab and field tested in three countries. It thrives in paddy crops such as barley, wheat, maize, and sugarcane. The fertiliser-produced food or liquids are returned to markets, sold, and consumed by households. This contributes to the development of an urban-rural link because the more people who urinate, the less we pollute the environment and wastewater treatment plants, and the less we rely on fresh water.
(Source: Down To Earth)
