No abstract

Both the high phosphorus (P) content and P bioavailability of the animal feed coproducts of the corn-ethanol industry could potentially contribute to increased manure and soil P levels and associated environmental issues (e.g., eutrophication). Therefore, a detailed modeling of total P mass flow to the coproducts (i.e., dry distillers grains with solubles, DDGS) was performed. Distribution of P between inorganic P and phytase-hydrolyzable P forms was quantified for selected coproducts (thin stillage, DDGS, modified DDGS [mDDGS]). The P mass balance indicated that although corn is the major P contributor to the coproducts (80.2%), a substantial portion (19.4%) comes from yeast addition. Of the two components constituting DDGS, wet distillers grains and condensed solubles, the latter contributes to only one-third of the mass but, importantly, yields 70.9% of P. The phytase enzyme used, , was very effective in hydrolyzing the nonorthophosphate P components of thin stillage, DDGS and mDDGS. Our results would help track P movement during various dry-grind processing steps and formulate strategies for phytase enzyme supplementation to various postfermentation coproducts from corn-ethanol plants.

No abstract

Manure characteristics change through processing, including anaerobic digestion (AD). These changes can alter handling of manure during downstream operations. This study analyzed the density, total solids (TS) content, and volatile solids (VS) content of pre-digested and anaerobically digested dairy manure from seven dairy farms in Wisconsin. The density of pre-digested manure increased from 990 to 1065 kg m−3 as the TS level increased from 1.5% to 13.0%. Density and TS for pre-digested manure from facilities using separated solids as bedding were related with a linear model for TS ranging from 1.5% to 13.0% and with a polynomial model for TS ranging from 1.5% to 50%. The model shows that density decreases with an increasing TS content when TS is greater than 8.0%. Manure from dairy facilities that used sand bedding had a VS/TS ratio of 0.87. This ratio was higher than the ratio when manure solids were used as bedding (0.81) and when food waste was incorporated into the digester (0.77). This study also provides a simple methodology to estimate biogas yield by using the density of pre- and post-digested manure.

The potential use of commercial enzyme and pH control has been investigated for enhancing dairy manure fermentation and modeling dissolved organic matter and orthophosphate (PO4-P) dynamics of fermenters. Anaerobic lab-scale batch fermenters (initial total solids concentration (TSo) = 3.8 wt. %) were fed with separated dairy manure solids and operated under pH controls (5 and 9.5). The enzymesupplemented alkaline fermenters clearly outperformed the acidic fermenters in terms of chemical oxygen demand (COD) solubilization: ca. 50% vs. 20%, respectively. Soluble PO4-P in the acidic fermenters was comparably higher but constituted less than 20% of total phosphorus. Better soluble COD (>80%) and soluble PO4-P (>70%) yields were noted for the dilute fermenters (TSo = 0.6-0.8 wt. %). An existing model was retrofitted, calibrated and validated for simulating dynamics of soluble COD, volatile fatty acids, and soluble orthophosphate under various pH and enzyme conditions. SYMBOLS Ceconcentration of hydrolytic enzymes, mg COD·dm -3 Cis concentration of insoluble substrate, mg COD·dm -3 Cmo concentration of monomer species, mg COD·dm -3 CNH 4 -Nconcentration of ammonia, mg N·dm -3 Cpp concentration of particulate orthophosphate, mg P·dm -3 Cprot -Nitrogen content of particulate proteins, mg N·dm -3 Csp concentration of soluble orthophosphate, mg P·dm -3 Css concentration of high-molecular-weight soluble substrate, mg COD·dm -3 . 156 K. GUNGOR et al. CVFAconcentration of volatile fatty acids, mg COD·dm -3 CXa concentration of acidogenic bacteria, mg COD·dm -3 CXmconcentration of methanogenic bacteria, mg COD·dm -3 kammammonification rate constant for proteins, d -1 kdis dissolution rate constant for particulate orthophosphate, d -1 kh,is hydrolysis rate constant for insoluble substrate, d -1 kh,s hydrolysis rate constant for soluble substrate, dm 3 ·mg -1 ·d -1 kpre precipitation rate constant for dissolved orthophosphate, d -1 µmax,amaximum specific growth rate for acidogens, d -1 µmax,mmaximum specific growth rate for methanogens, d -1 Ka half-saturation coefficient for monomer species, mg COD·dm -3 Km half-saturation coefficient for volatile fatty acids, mg COD·dm -3 Kn half-saturation coefficient for ammonia, mg N·dm -3 Yayield for acidogens on monomer species, g COD·g -1 COD Ym yield for methanogens on VFAs, g COD·g -1 COD YN/Xweight fraction of nitrogen in bacterial cell, g N·g -1 COD da decay rate constant for acidogens, d -1 dm decay rate constant for methanogens, d -1