A biorefinery approach to recover nutrients, proteins, and methane from raw swine manure

The livestock industry is expanding rapidly, generating large amounts of manure rich in nutrients and energy. This study develops a novel integrated biorefinery approach that combines multiple technologies to enable the simultaneous recovery of nutrients, proteins and energy from pig manure, maximizing resource valorization and economic returns. The technologies included gas-permeable membrane (GPM) to separate the ammonia, solid-liquid separation to separate organic particles, acid-base solubilization to separate phosphorus and proteins (SPP) from the particles, anaerobic digestion (AD) to produce biogas and combinations thereof. Using the GPM method, nitrogen (N) concentrations were reduced by up to 90 %, with total ammonia nitrogen (TAN) recovery rates ranging from 25 to 27 g N m −2 d −1 . Solid-liquid separation did not significantly increase pH or N recovery. The SPP method provided a phosphorus extraction efficiency of 114 % and a protein extraction efficiency of 86 % from the solid fraction of pig manure. The methane yield was 1.9 times higher when nitrogen was recovered before AD, while phosphorus and protein removal resulted in methane yields comparable to swine manure (215.5 mL CH 4 g −1 VS). A techno-economical study was carried out for the AD treatments proposed in the biorefinery approach. High internal rates of return (IRR) were obtained, 21–37 %, and a return on the investment in 3–5 years was obtained for all the treatments. This integrated strategy demonstrated a comprehensive and economically viable solution for sustainable pig manure management and resource recovery. • A biorefinery approach is developed for pig manure valorization combining different technologies. • Nitrogen (N) was reduced up to 90 %, with N recovery rates ranging from 25 to 27 g N m −2 d −1 . • Up to 100 % of the phosphorus and 86 % of protein were recovery by a novel method of separation (SPP). • N recovery before anaerobic digestion increased CH 4 yield by 1.9 times compared to swine manure. • Techno-economic analysis revealed a rapid investment payback (3–5 years) for AD treatments.