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Title: Evaluation of methane production from wet stillage and the nutritional value of the residue. Final report

Technical Report ·
DOI:https://doi.org/10.2172/6783019· OSTI ID:6783019

Wet stillage was obtained from a farm still at Campo, Colorado that used both corn and milo as feedstocks. The mash was passed through the still and the stillage was run through a screw press which resulted in two streams: a solid fraction containing about 38% solids and a thin stillage fraction containing 5% silo. Methane production was evaluated in a laboratory fermenter of 1-L capacity for samples of the solid fraction and for one sample of the thin stillage. The original stillage and the residue remaining after methane digestion were evaluated as livestock feed by means of the standard in vitro dry matter digestibility method (IVDMD). Methane represented 50 to 70% of the gas production. Methane production ranged from 300 to 500 L/kg of solids after fermenting 22 to 24 days, and was essentially the same whether crop or milo was the feedstock. One sample of thin stillage performed similar to the solid fraction on dry matter basis. The IVDMD of the original stillage averaged 53%, while the residue after methane digestion was only 12%. An economic analysis based upon current prices and the data from this experiment indicated that the total stillage produced from one bushel of grain (25 kg) would be valued at $1.29 as a protein supplement for cattle, 30 cents as fertilizer, or 32 cents, 76 cents, or 88 cents respectively as a replacement for natural gas, propane, or diesel fuel. The same amount of grain would also leave 5% dry matter, for a value of 19 cents as livestock feed and 17 cents as a replacement for propane. Based on these conclusions, we recommend pressing the stillage, feeding the solids to ruminant animals, and fermenting the liquid for methane, which may provide one fourth of the energy for distillation.

Research Organization:
Colorado State Univ., Fort Collins, CO (United States)
DOE Contract Number:
AC02-77CH00178
OSTI ID:
6783019
Report Number(s):
SERI/TR-09076-1
Country of Publication:
United States
Language:
English

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