In any discussion of the enzymatic approach for biodiesel, one comes across two major bottlenecks. The first is the deactivation of the biocatalyst, usually within a period so short that the whole process is deemed to be not cost-effective. The second bottleneck is the high cost of enzyme and the cost associated with its need for con­stant replacement.

In studies conducted by SBC, the lipase is observed to be deactivated due to glycerol, methanol or ethanol when inert solvent is absent. When the reaction pro­ceeds to form the product, glycerol droplets present as a secondary phase gradually poison the catalyst. Some techniques make use of dilute portions of the lipase in a CSTR design to avoid this problem. However, all this does is lower the probability of contact between catalyst and glycerol. The disadvantage is the increased reaction time, which can be prolonged to several hours. If the reaction time is to be short­ened, a higher amount of lipase will have to be used. However, in this case, glycerol amount will also increase rapidly, thereby deactivating the catalyst. Shifting to a packed bed design will result in glycerol clogging up the bottom of the reactor after the reaction progresses for quite some time.

In the ET Process®, the problem of catalyst poisoning is solved with the use of an inert solvent. The solvent dissolves glycerol and produces a homogeneous solution. Without a secondary phase, the immobilized lipase maintains optimum performance and converts 100% of the oil (natural triglyceride and FFA) into products. The short reaction time and long lipase life span are two of the most important features of a tech­nology that is industrially viable and competitive in the market. Without the use of the inert solvent, the lipase cost problem cannot be overcome. Both CSTR and packed bed design can be used with the inert solvent, although the latter is more highly preferred.

Another feature that can complete the formation of a sustainable, green energy business is low cost. That cost is important is undeniable. In the history of any green energy business, novel ideas alone cannot force mass adaptability of a technology. The solution to fossil fuel dependence needs to address not just environmental con­cern but also economic practicality. Only then will it have widespread use and be called a truly sustainable technology.

Characteristics of the immobilized lipase used in the ET Process® are good enough to render its cost contribution in the process insignificant over its life span. The current lipase cost is USD 350/kg. Over the lifetime within which the immobi­lized lipase is used, the cost contribution to the biodiesel product will be USD 0.029/ kg or less. A further extension to 18 months will decrease it to USD 0.019/kg. To date, there are more than ten different lipases that could meet the requirements of

the process. When this kind of biocatalyst is regularly used in the future, mass pro­duction will reduce the cost even more.

The value of the technology is in its pioneering method of prolonging biocatalyst life span and, in doing so, minimizing the operating cost. This is previously unreach­able with an enzymatic biodiesel process. Another significant effect is the reduced cost allocation for the feedstock. The enzymatic process allows for flexible feedstock acceptance, such that oils with high FFA content can be used without expensive purification steps.

In the past, a biodiesel production system assigns 70-90% of expenses to feed­stock procurement. Sourcing is affected by strict requirements for low FFA level and low water content, while output is affected by catalyst removal, soap formation and absence of profitable co-products. The ET Process® can reduce feedstock cost allocation to lower than 50%. This is the major cost-saving factor. The profit­boosting factor comes from the co-production of pharma-grade glycerol, phyto­chemicals and zoochemicals. The mild reaction inherent to the enzymatic process and absence of basic and acidic catalysts allow these substances to be extracted through downstream processing. Other applications can also produce high value — added products like fatty acid isopropyl esters or similar products from the reaction of oil with higher alcohol reactants.

Table 11.3 Typical composition of crude palm oil (Hui 1996)