Two real-world issues involving the use of biodiesel

There are a number of different feed stocks (methyl esters, refined canola oil, french fry oil, etc.) that are used to produce biodiesel, but in the end they all have a few common problems.

First, any of the biodiesel products have a problem of gelling when the temperatures get below 40 °F (4.4 °C) or so, depending on the mix of esters. At the present time there is no available product that will significantly lower the gel point of straight biodiesel. A number of studies have concluded that winter operations require a blend of bio, #2 low sulfur diesel fuel, and #1 kerosene. The exact blend depends on the operating environment: successful operations have run using a 65% LS #2, 30% K #1, and 5% bio blend. Other areas have run a 70% LS #2, 20% K #1, and 10% bio blend or a 80% K#1, and 20% bio blend. Factors in choosing a blend include volume, component availability, and local economics.

The second problem with biodiesel is that it is hydrophilic. Some of the water present is residual to processing, and some comes from storage tank condensation. The presence of water in biodiesel is a problem for a number of reasons:

• Water reduces the heat of combustion. This means more smoke, harder starting, less power.
• Water will cause corrosion of vital fuel system components: fuel pumps, injector pumps, fuel lines, etc.
• Water, as it approaches 32 °F (0 °C) begins to form ice crystals. These crystals provide sites of nucleation and accelerate the gelling of the residual fuel.
• Water is part of the respiration system of most microbes. Biodiesel is a great food for microbes, so the presence of water accelerates the growth of microbe colonies which can plug up a fuel system. Biodiesel users who have heated fuel tanks therefore face a year-round microbe problem.