Two Stage Base / Base Biodiesel Recipes

Improving Quality

If you find you’re having trouble making biodiesel to the quality you desire, you may want to consider the Base/Base method. This method is nothing more than splitting the mixing into two steps with a portion of the methoxide used on each step.

Since Transesterification is reversible, we need an excess of methanol to ensure complete conversion. With more methanol present than glycerine we ensure that our reaction goes the way we want. The Base/Base method is another way to improve the reaction by shifting the ratio of glycerine to methanol even further in favor of methanol and complete reaction.

Recipe:

Determine your recipe just like you would for your normal single stage recipe with whatever percentage of methanol you are using and NaOH or KOH according to your normal procedure. Mix up your methoxide and divide it into two containers. The first container containing 80% of your methoxide and the second containing the remaining 20% of your methoxide.

Process

Notes

This method was initially from the University of Iowa. However, the researchers there strongly favor the acid/base method over the base/base method. This is primarily due to the dramatically improved economics of the acid/base method in a commercial setting. The biggest advantage of this method over the acid base method is that we don’t need to use acids in the process. That means one less hazardous material to stock in our production areas.

Reducing Methanol Consumption

If your quality is acceptable and you desire to reduce your methanol consumption, you can use this process to maintain your quality while reducing the methanol used.

Here we have a different approach to building the recipe. In this case we are aiming for the minimum methanol and catalyst we can use in the first stage and still obtain a good separation. It takes at least 14% methanol to consistently achieve separation with good mixing. If you have trouble making high quality fuel then increase the amount of methanol you use in the first stage slightly and you should improve. In order to adjust for the fact that higher titration oils may not separate every time we multiply the titration value by 1.15 for the first stage.

The second stage will not change with the titration since we have converted all the FFA to soap in the first stage, so we use the same recipe on the second stage no matter the titration.

The Recipe

The Process

The process will be the same as described earlier for the 80/20 method.

Both of these methods are more time consuming and make more soap than the single stage base method we normally use, but can either increase the conversion level of our fuel or reduce methanol consumption.