Phosphorus reclamation through hydrothermal carbonization of animal manures.

Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from large farms was investigated as a scenario for the reclamation of phosphate for agricultural use and mitigation of the negative environmental impact of phosphate pollution. Hydrothermal reaction conditions were identified for poultry, swine, and cattle manures that resulted in hydrochar yields of 50-60% for all three manures, and >90% of the total phosphorus present in these systems was contained in the hydrochars as precipitated phosphate salts. Phosphate recovery was achieved in yields of 80-90% by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Phosphate recovery was achieved in yields of 81-87% based on starting manures by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Swine and cattle manures produced hydrochars with combustion energy contents comparable to those of high-end sub-bituminous coals.

Industrial symbiosis: corn ethanol fermentation, hydrothermal carbonization, and anaerobic digestion.

The production of dry-grind corn ethanol results in the generation of intermediate products, thin and whole stillage, which require energy-intensive downstream processing for conversion into commercial animal feed products. Hydrothermal carbonization of thin and whole stillage coupled with anaerobic digestion was investigated as alternative processing methods that could benefit the industry. By substantially eliminating evaporation of water, reductions in downstream energy consumption from 65% to 73% were achieved while generating hydrochar, fatty acids, treated process water, and biogas co-products providing new opportunities for the industry. Processing whole stillage in this manner produced the four co-products, eliminated centrifugation and evaporation, and substantially reduced drying. With thin stillage, all four co-products were again produced, as well as a high quality animal feed. Anaerobic digestion of the aqueous product stream from the hydrothermal carbonization of thin stillage reduced chemical oxygen demand (COD) by more than 90% and converted 83% of the initial COD to methane. Internal use of this biogas could entirely fuel the HTC process and reduce overall natural gas usage.

Salt tolerant membrane adsorbers for robust impurity clearance.

Clearance of impurities such as viruses, host cell protein (HCP), and DNA is a critical purification design consideration for manufacture of monoclonal antibody therapeutics. Anion exchange chromatography has frequently been utilized to accomplish this goal; however, anion exchange adsorbents based on the traditional quaternary amine (Q) ligand are sensitive to salt concentration, leading to reduced clearance levels of impurities at moderate salt concentrations (50-150 mM). In this report, membrane adsorbers incorporating four alternative salt tolerant anion exchange ligands were examined for impurity clearance: agmatine, tris-2-aminoethyl amine, polyhexamethylene biguanide (PHMB), and polyethyleneimine. Each of these ligands provided greater than 5 log reduction value (LRV) for viral clearance of phage phiX174 (pI approximately 6.7) at pH 7.5 and phage PR772 (pI approximately 4) at pH 4.2 in the presence of salt. Under these same conditions, the commercial Q membrane adsorber provided no clearance (zero LRV). Clearance of host-cell protein at pH 7.5 was the most challenging test case; only PHMB maintained 1.5 LRV in 150 mM salt. The salt tolerance of PHMB was attributed to its large positive net charge through the presence of multiple biguanide groups that participated in electrostatic and hydrogen bonding interactions with the impurity molecules. On the basis of the results of this study, membrane adsorbers that incorporate salt tolerant anion exchange ligands provide a robust approach to impurity clearance during the purification of monoclonal antibodies.