BioDiesel

Overview:
Bio-diesel is developing into one of the most important bio-fuels of the future. This is because virtually all industrial vehicles used for farming, transport and trade are diesel-based. Currently, bio-diesel is produced from animal or plant oils in a reaction known as transesterification. Oils are first extracted from the plant and then reacted with methanol and a catalyst such as sodium methoxide to produce bio-diesel and glycerol¹. Bio-diesel is considered to be an excellent renewable carbon-neutral fuel, but to enhance its economic viability, improved production systems must be developed.

In the past decade, the bio-diesel industry has seen massive growth both in Australia and globally. The increased demand for vegetable oils for the production of bio-diesel has lead to significant pressure on the domestic vegetable oil market. In response to this, a number of crops are now being grown solely for the purpose of bio-diesel production, most notably soy, canola, jatropha and palm oil. With more crops being dedicated to production of bio-fuels, increasing pressure is being put on the food supply. Eventually the combined pressure of food and fuel production is predicted to produce a phenomenon known as ‘peak soil’. With only 13.3% of the world’s land mass considered to be arable, and oil-producing crops being specific to certain climates, it is not possible for land-based plants to meet global fuel demand alone.

Algal production systems have long been recognised as the most efficient means of producing biomass for food or fuel; they do not require arable land and therefore don’t compete for space with existing crops. Over the same area micro algae can produce 20-300 times more bio-diesel than traditional crops (Table 1) and the remaining algal cake can still be useful for animal feed, fertiliser or other bio-fuel production systems. However, the initial set-up and maintenance of such systems has, to date, always proven to be cost prohibitive for fuel.

Table 1: Comparison between crop efficiencies for bio-diesel production ^2,3

Plant Source	Bio-diesel (L/Hect/Year)	Area required to match current global oil demand (million hectares)	Area required as a percentage of global land mass
Soybean	446	10932	72.9
Rapeseed	119	4097	27.3
Mustard	1300	3750	25.0
Jatropha	1892	2577	17.2
Palm Oil	5950	819	5.5
Algae (low)	45000	108	0.7
Algae (high)	137000	36	0.2

Common stream:
The first stage of all bio-fuel production is the production of biomass. Following the modules set out for improving photosynthetic efficiency, we will be utilising methods developed in the bio-hydrogen project to modify algal species best suited for bio-diesel production.

Specific stream:
The Solar Bio-fuels Consortium is building up a large collection of local algal species from marine, brackish and fresh water environments. Each of the isolated species is being grown under a variety of conditions and then screened for properties desirable for bio-fuel production. Using scaled-up systems, the most promising local strains are being compared to the highest oil-producing algal species for bio-fuel production from around the world. The key properties being screened include:

Efficiency of oil production
Engineering-improved light capture efficiency
Engineering-improved salt tolerance
Growth rates
Resistance to fluctuating climatic conditions
Competitiveness in mixed culture
Valuable by-products (eg. protein and carbohydrate composition, as the processed algal cake can be further utilised for animal feed, fertiliser or in other bio-fuel production systems
Bio-reactor design

References:

Fukuda, H., Kondo, A. & Noda, H. (2001) Biodiesel fuel production by transesterification of oils. J Biosci Bioeng 92: 405–16.

Sheehan, J., Dunahay, T., Benemann, J. & Roessler, P. (1998) A look back at the U.S. Department of Energy's Aquatic Species Program—biodiesel from algae. National Renewable Energy Laboratory, Golden, CO; Report NREL/TP-580–24190.

Chisti Y. (2007) Biodiesel from microalgae. Biotechnol Adv 25: 294–306.