Biodiesel How to Make Biodiesel Biodiesel Byproducts
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Biodiesel Byproducts.
A Byproduct of the manufacture of Biodiesel is a mixture of Glycerine, methanol and the catalyst used.. After the transesterification process the oil seperates into a layer of biodiesel and a layer of this glycerine mixture. This however is not pure glycerine, it will contain some methanol, sodium hydroxide and soap. Some places will buy it from you like this and purify it themselves if you are lucky. If not you will have to purify it yourself. To seperate the glycerine from the lye and soaps you will need to add some Phosphoric acid (H3PO4) to it. This will break down the soaps back to Free Fatty Acids (FFA's) and leave you with three distinct layers. Lye/Phosphorus at the bottom Glycerine/methanol in the middle and FFA's at the top. To recover the Methanol from the glycerine and use it in a next batch you will have to heat the mixture to above 65°C (150°F). Don't breath any of the fumes. Use a closed container and let the methanol fumes run through a simple condenser to turn the methanol gas back into a liquid. The amount of Phosphoric acid required will depend on the amount of catalyst used and the purity of the phosphoric acid. The most common purity is 85%. A general rule is, if using 85% phoshoric acid, to use one and a half times the amount of Sodium hydroxide used. For example if you used 6 grams of catalyst per liter of oil you will need 9 grams of Phosohoric acid to seperate the glycerine. 6 x 1.5 = 9 grams per liter of oil used. That means if you used 100 litre of oil to make biodiesel you will need 900 mililiters of Phosphoric acid. Add the acid to the glycerine mixture and watch how it seperates into three layers first the Free fatty acids will form at the top. Allow at least twelve hours for the whole process to be complete. When the seperation is complete you can drain the different layers. What can I do with the Byproducts? The Free Fatty Acids burns very well so it can be used as a heating fuel. It can also be used as a fertiliser. It works best in a hot compost heap with other plant material. The Catalyst reacts with the phosphoric acid to form Sodium Phosphates if you used Sodium Hydroxide as a Catalyst or Potassium Phosphates if you used Potassium Hydroxide. Both Sodium and Potassium Phosphates makes a great fertiliser but just like the FFA's it is beter to use a hot compost heap. The Glycerine layer will still contain some methanol in it that can be reclaimed. Make a simple condenser. Heat the Glycerine/methanol mixture to above 65°C (150°F) to evaporate the methanol through the condenser. Be careful not to breath the fumes. Do this until all the methanol has evaporated. It is not neccesary to seperate the FFA's and Catalyst before this process, but if you do this process first seperating the FFA's and Catalyst will be very difficult. What can I do with Glycerine? Pure Glycerine has a great number of uses.
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