We operate a pre-treatment (dissolved air flotation) unit for an agri-food plant that specializes in duck.
The process works well, even too well, because although a significant amount of animal fat is recovered, it is thick and hardens quickly in the 15-m3 storage tank, which is emptied once a week. This translates into a huge problem for the vacuum trucks when it comes time to pump out the fat.
Hence our question: is there a solution that would allow these fats to remain sufficiently liquid so they could be pumped more easily?
Full disclosure: my knowledge of the subject is only from reading the literature. A lot of food processing plants use insulated stainless steel tanks to store fats. Some are heated using steam injection. Maintaining a minimum temperature for solubility in your storage tank might be an avenue to explore.
Does the duck fat congeal in both summer and winter? (critical temperature). Does it congeal uniformly?
To answer your questions: It is an underground tank, and the fat solidifies in both summer and winter (though obviously more in the latter). The melting point is > 20 °C. In the tank, the entire layer of fat congeals (at least over 2 m and below it is more liquid because it has a higher water content), and it does so across the whole surface as well. The vacuum trucks can only pump out the fat if they inject water at the same time. Of course maintaining the tank at a temperature of at least 25°C is the ideal solution but that demands a big investment and high operating costs, which the company is not prepared to incur. They prefer to pay additional pumping time.
Is there an ideal distance over which fat can be transfered without risking fatbergs?