Waste streams have traditionally been considered a source of pollutants to environmental systems. Poultry litter has been a topic of recent interest in Israel and the U.S. due to high nutrient loads in waste-runoff from agricultural areas.
Moreover, the Phosphorus present in the poultry litter is a non-renewable resource that is critical for global food security. Unfortunately, majority of the world’s phosphorus supply stems from phosphorus-rich ores, whose geographical distribution is highly skewed. More importantly, these deposits are rapidly being depleted. If current usage trends continue, the world will run out of mineable phosphorus supplies in the next hundred years. And that will result in an unprecedented global crisis.
A joint BARD-funded collaboration, led by Dr. Sukalyan Sengupta from University of Massachusetts Dartmouth and Dr. Beni Lew from ARO, together with Dr. Lee Blaney from University of Maryland Baltimore County, aimed at investigating possibilities of a hybrid technology that will provide a solution both for continuous-flow treatment of poultry litter, and for high recovery of phosphorus. The researchers want to do so by shifting nutrient loading issues into potential resource/revenue streams. They believe that progress in reducing nutrient loads to sensitive ecosystems can be accelerated. Two pilot-scale facilities were involved in testing these techniques, one in Israel, and the other in the U.S.
The project’s hypothesis was that phosphorus can be sustainably recovered from concentrated poultry litter using a two-phase process. This process consists of a Phosphorus Extraction and Recovery System (PEARS), which allows for phosphorus release from poultry litter and subsequent precipitation as a high-value product, and a hybrid ion exchange, Hydrated Ferric Oxide - Polymeric Ligand Exchanger (HFO-PLE) unit that treats the PEARS effluent to ensure low-phosphorus content, Figures 1 & 2.
The hypothesis was tested through the following steps. First, optimizing and modeling the process chemistry for PEARS to produce struvite and potassium struvite from poultry litter. Then, achieving additional phosphorus recovery from PEARS effluent using specialty polymeric ligand exchangers impregnated with hydrated ferric oxide. Once this was done, the researchers wanted to determine the purity of the recovered phosphorus product and explore the sustainable reuse of extraction and regeneration solutions.
The next steps in the plan were to develop a start-up program for two PEARS-HAIX pilots, one in Israel, and the other in the United States, to determine potential nutrient load reductions in the Kineret Lake (Israel) and the Chesapeake Bay (US) watersheds. The overall phosphorus recovery rate achieved in this pilot-scale reactor was > 80%, rising to > 90% under certain conditions.
Fig. 1: Schematic of the PEARS-HAIX zero-waste system for phosphorus recovery.
Figure 2: PEARS Reactor