CRUDE GLYCERIN

The two major uses of crude glycerin are as a fuel and as a feedstock for making purified glycerin.   Crude glycerin can obviously be purified, but the main way of doing this is through distillation, optionally with vacuum.  However, it's very energy intensive.  Prior to the buildup and rise of biodiesel in the US, Europe and Southeast Asia, glycerin was considered a high-value chemical ingredient and was mainly refined from soapmaking glycerin.  Afterwards, its value dropped precipitously to the point where the price is almost entirely determined by the cost of energy rather than the cost of the raw material. Crude glycerin has a positive heating value despite all of the water in it, but because of the necessity of absorbing all of that heat capacity can only realistically be combusted if it is co-fired in a very large burner.  In addition, it often has a witch's brew of other components including a high ion content (which translates into ash).  As a result its actual heating value in monetary terms is so low that few places can handle it.