Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/28/2013
Publication Date: 8/23/2013
Citation: Haas, M.J., Stroup, R.L., Latshaw, D. 2013. Soybean meal retains its nutritional value as an animal feed following its use for biodiesel production via in situ transesterification. Journal of the American Oil Chemists' Society. 90, Issue 9, p.1343-1349. Interpretive Summary: We and other researchers have recently been developing a new approach for biodiesel production called “in situ transesterification” or “direct transesterification.” In this new method, biodiesel is produced directly from a fat- or oil-containing agricultural material. In the older, conventional biodiesel production process, the fat or oil is first extracted from the agricultural material, then purified and finally converted into biodiesel. Our new “direct” method is potentially attractive because it eliminates the necessity of some process steps that are found in today’s conventional technologies, and thus could reduce the cost of biodiesel production. However, as in all biodiesel production methods, the sale of fuel itself will not generate sufficient funds to make the overall process economically affordable. Rather, economic profitability will be derived from the additional sale of coproducts of the reaction. In the case of in situ transesterification the coproduct is the fat-free residue (meal) left over after conversion of the fat in the feedstock into biodiesel. A common use for agricultural meals is as an ingredient in feeds for swine, poultry, beef and dairy animals. In the work reported here, using soybeans as a feedstock, we investigated the suitability of the meal exiting an in situ transesterification reaction as a component of poultry diets. The meal was found to perform comparably to the soybean meals currently prevalent in poultry nutrition. This, and similar prior work involving rainbow trout conducted by our group, are the only reported investigations to explore and establish the possibility of a market value for the meal coproduct of in situ transesterification. These data could foster adoption of this new, potentially cost saving, approach to biodiesel production.
Technical Abstract: The suitability in poultry nutrition of the lipid-depleted meal generated by in situ transesterification of flaked soybeans to produce biodiesel was examined. For purposes of comparison, analogous diets were formulated using flaked soybeans whose lipid had been removed by conventional industrial hexane extraction. Each test group consisted of 300 newly hatched broiler chicks of both sexes. The duration of feeding was 42 days, during which two diets, a starter formulation (1- 21 days) and a grower formulation (22 - 42 days) were fed. In situ transesterification removed over 97% of the lipid from the soybean flakes. Trypsin inhibitor was successfully denatured by steaming. The residual lysine levels in the transesterified flakes were comparable to that reported for soybeans, indicating that the transesterification process had probably not caused widespread damage to the proteins and fatty acids in the sample. Chicks accepted both the test and control diets, and no acute toxicities occurred. Weight gain, feed consumption and feed efficiency were generally comparable between the two test groups, with no more than a 3 - 4% difference at the starter and grower diet phases. Over the entire duration of the trial there was no significant difference between the ratios of feed consumed to weight gained for the two test groups. Mortalities within the group receiving transesterified meal exceeded those in the hexane-extracted meal group (6.8% vs. 3.4%) but may have been influenced by excessive temperatures in the last week of the trial. In general, soybean meal that has been subjected to in situ transesterification appears to be an acceptable component of poultry diets.