Glycerol, also known as glycerin, can be obtained through biodiesel production from vegetable oils or animal fats.
Through a process called “transesterification,” the fatty acids are separated from glycerol and re-esterified into an alcohol known as methanol, leaving glycerol as a residue.
For every 100 kg of biodiesel produced, approximately 4 to 10kg of glycerol is obtained.
With the growth of the biodiesel industry, the use of glycerol in livestock diets is gaining increasing interest due to its greater availability and more favorable prices.
This by-product is a viscous liquid that needs to be stored at temperatures above 13°C to ensure fluidity.
According to the FAO, glycerol is recognized as a safe ingredient for animal diets. However, the levels of methanol found in this by-product obtained from biodiesel production must be taken into account.
Its purity depends on the processes to which it is subjected to. The higher the purity, the lower the methanol content it contains.
This is why variable levels of methanol can be found, ranging from 1.3% to 27%. The latter is an undesirable alcohol for livestock feed due to its toxicity.
In ruminants, methanol toxicity is lower than in monogastric animals, thanks to ruminal bacteria that can detoxify this alcohol. However, under the presence of high doses or in unaccustomed animals, renal and nervous disorders may occur.
Glycerol as a nutrient
It is classified as a concentrated and energy-rich feed ingredient. Its water content varies but never exceeds 27% (Table 1).
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