Producing ready-to-use phosphorus fertilizer from food waste, fish entrails, and dewatered nightsoil sludge

Types of food materials: Food waste, fish entrails, dewatered nightsoil sludge
Product obtained from research: Phosphorus fertilizer

In 2020, Thailand imported around 5,141,100 tons of chemical fertilizers valued at over 46,342 million baht (DOA, 2020), leading to an increased demand for phosphorus. The world’s phosphorus deposits are diminishing and are expected to be exhausted within 50–100 years (Cordell et al., 2009). The shortage of phosphorus in global sources directly impacts food security in Thailand. This is because the agricultural sector requires phosphorus fertilizer as the main component for cultivation.

Organic waste, including food waste from cooking and eating, and fish entrails from markets and factories, is often disposed of with general waste. This leads to an increase in the overall waste volume and creates a burden for disposal. Therefore, proper waste separation is crucial for maximizing utilization and adding value to organic waste, resulting in more efficient overall waste management.

This study aims to recover phosphorus from organic waste sources such as food waste, fish entrails, and dewatered nightsoil sludge. The process involves anaerobic biodegradation and the crystallization of chemical phosphorus fertilizers. This process transforms accumulated waste phosphorus into a crystalline form, making it a ready-to-use fertilizer that is convenient for transportation. The chemical properties of phosphorus fertilizers derived from this study closely resemble to those of commercial fertilizers and can facilitate biogas production through anaerobic co-fermentation. The economic evaluation found that the process can be further developed or expanded to generate profits in the future, especially if the market price of fertilizer increases above $13.5 or 493 baht/kg P. (exchange rate 36.5 baht/1 USD).

Picture of a struvite crystal formation reaction tank.

The Project of Process technology for Phosphorus crystallization from food waste and dewatered nightsoil sludge
Research supported by National Research Council of Thailand, Fiscal year 2022

Researcher
Assoc. Prof. Dr. Supawadee Polprasert
Department of Environmental Health Sciences, Faculty of Public Health, Mahidol University
420/1 Ratchawithi Road, Thung Phaya Thai Subdistrict, Ratchathewi District, Bangkok 10400 
Tel: 084-527 2277, Fax: 02-354 8525, Email: supawadee.pol@mahidol.ac.th