Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING THE PERFORMANCE OF ALTERNATIVE FUELS AND CO-PRODUCTS FROM VEGETABLE OILS Title: Biodiesel Supplement

Author
item Knothe, Gerhard

Submitted to: Inform
Publication Type: Popular Publication
Publication Acceptance Date: August 20, 2007
Publication Date: September 1, 1987
Citation: Knothe, G.H. 1987. Biodiesel Supplement. Inform.

Technical Abstract: 1. What are the greatest challenges facing the biodiesel industry today? The greatest challenges are probably related to the amount of feedstock being available if the current expansion in biodiesel production and use continues. This challenge is addressed below under question 2 regarding the hurdles biodiesel needs to overcome in order to become a mainstream energy source. However, the feedstock challenge entails a variety of other issues. For example, with increasing production and demand for biodiesel feedstocks, the price of the these commodities also tends to increase. Thus the cost differential between petrodiesel and biodiesel can remain even in times of rising petroleum prices. Another issue is the question of production capacity. With new biodiesel plants, quite a few of them large-scale entities, being announced on a regular basis, the question must be asked if an overcapacity will exist, with all possible consequences for the industry. 2. Can biodiesel become a mainstream energy source, and what hurdles must be overcome to achieve that goal? The major hurdle that biodiesel faces in becoming a mainstream energy source (assuming that the word "mainstream" connotes a significant amount of overall energy demand, say 20%, is derived from a certain source) is the amount of available feedstock. However, one may see biodiesel as a mainstream energy source among the "alternative" energy sources. The hurdle of biodiesel becoming such a mainstream energy source is not easy to overcome. Vegetable oils will always have other uses besides being an energy source, foremost, of course, serving human nutrition needs, which raises the well-known food vs. fuel issue. Thus only a fraction of vegetable oil production is available for non-food uses, including fuel applications. Obvious approaches to easing the supply problem are increasing yield per unit of land and increasing the amount of land that is farmed. Especially the latter approach faces natural limits because not all land is suitable for agricultural production, and there is a finite amount of available land anyway. In the case of palm oil, concerns have been raised that cutting down tropical rain forests in order to grow more palms, has a negative carbon footprint. Another approach is to use feedstocks such as used frying oils, animal fats, soapstock, greases, etc., but these feedstocks do not represent any breakthroughs in terms of availability. The utilization of algae is still many years down the road. Besides modifications to production depending on the feedstock, another issue is that many feedstocks do not possess favorable properties, especially cold flow. 3. We have heard a lot lately from petroleum companies desiring to use agricultural lipids to produce alkane petroleum-like fuels. Do you view these as comparable, superior, or inferior to biodiesel? There are advantages and disadvantages of this approach. Advantages of petrodiesel-like fuels are that they usually possess better cold-flow properties and better oxidative stability. Furthermore, they likely face less obstacles gaining acceptance by engine manufacturers. However, many of the biodiesel-typical advantages are lost when using these fuels. These advantages of biodiesel are biodegradability, inherent lubricity, higher flash point, reduction of most regulated exhaust emissions (with the exception of NOx). The energy balance of the petrodiesel-like fuels from biological sources is very likely less favorable than that of biodiesel since the petrodiesel-like fuels are usually produced using high pressure and high temperature. Overall, the use of agricultural lipids for this purpose appears to be a waste of these feedstocks. It appears more reasonable to produce petrodiesel-like fuels from another biomass that would otherwise serve no use. The petrodiesel-like fuels derived from such biomass could find application as aviation fuels, where favorable cold-flow properties are important. Biodiesel is very suitable for surface applications, where its environmentally benign properties give it a distinct advantage in applications such as underground mining, use in environmentally sensitive areas (national parks, etc.), or in marine engines. As a final note, petrodiesel-like fuels from agricultural lipids have in some cases been referred to as "second-generation biodiesel" but this term is a misnomer because these fuels do not meet the definition of biodiesel being the "mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats" (definition per biodiesel standard ASTM D6751).

Last Modified: 7/31/2014
Footer Content Back to Top of Page