Biomedical Engineering Reference
In-Depth Information
by Yang et al (2007). The test biodiesel (B20) was blended with 80% diesel and 20%
methyl ester derived from waste cooking oil. The results presented that the average total
PAH emission factors were 1097 and 1437 μg bhp-h-1 for B20 and diesel, respectively. For
most ringed-PAHs and total-PAHs, B20 has lower PAH emission levels than that of diesel
fuel. For both B20 and diesel, total PAH emission levels decreased as the driving mileage
accumulated [6]. Some studies have shown also, that biodiesel may actually produce an
increase in NOx emissions as shown in Figure 3. However, this larely varies due to
composition of the fuel. In actuality, some fuels decrease emissions, while others are seen
to increase generalizing statement [4].
1.4. Challenges with Biodiesel
One of the challenges of the biodiesel industry is improving efficiency to make the
production cost-competitive with diesel [1]. In 2003, biodiesel cost over $0.50/l while
diesel cost $0.35/l [7]. This high cost is mostly due to the usage of virgin vegetable oil as
a feedstock [7]. Soybean oil cost $0.36/l in June 2002 [7]. This is already over the cost of
diesel. Using cheaper feedstocks, such as waste cooking oil, is seen as a promising way
of reducing cost, as they are estimated to be about half the cost of refined oils. The
obstacle with cheaper feedstocks is the higher content of FFA and other unwanted
ingredients. Although biodiesel has been proven profitable, but if there are more lucrative
alternatives, actors will not pursue it. The analysis focuses on quantifiable economic
costs and benefits driven by markets, since few production decisions in competitive
agricultural and fuels markets are driven by non-market logic. Situations in which non-
economic considerations might influence production decisions are noted. Table 1
considers the regional actors required to realize biodiesel production [8]. It shows that the
development and economic analysis of biodiesel industry can be influenced by several of
factors. Those factors are the major challenges for considerations of which shall be taken
priority.
2. Biodiesel Production
Methods such as pyrolysis, microemulsification, solid-liquid phase conversion, and
transetherification applied to reduce the high viscosity of vegetable oils to enable their
use in general diesel engines without operational problems have been investigated.
Transesterification is the most common technique used for biodiesel production. The
most commonly prepared esters ate methyl esters due to methanol is the least expensive
alcohol, although there are exceptions in some countries. Although those fresh or used
oils and fats can be suitable for biodiesel production; however, changes in the reaction
procedure frequently have to be made because the presence of water of free fatty acid
(FFA) in feedstocks. This section discusses the reaction based on transesterification
technologies.
