Know Your Enemy: a True Reflection on Testing in Renewable Feedstocks

Traditional tests (for example NACE TM0174 procedure B) have been used to evaluate long-term immersion performance of linings in the energy market to confirm performance. Experience has allowed results from these tests to correlate with long term performance in fossil fuel feedstocks (crude etc.). The same cannot be said about lipid-based feedstocks (waste cooking oil, beef tallow, vegetable oils etc.) where the rulebook goes out the window. The material you start testing is not the same as you finish with, as time and temperature have a ridiculous impact on composition and hence performance. Lipids start off innocuous and then they turn on you – degrading into free fatty acids (FFA) in the bulk and organic acids and others in the vapour. To make things worse water and oxygen support the degradation and an initially higher FFA content seems to accelerate the formation of more! A long-term immersion is, therefore, not necessarily the way to test these materials and it becomes necessary to develop tests that reflect what happens in real life where tanks are heated, there is water resent and the stored material will be refreshed (but is it?). Appropriate testing is therefore required to demonstrate the performance of linings.