Table 6-1. Oilseed crop typical yields and land requirements for self-sufficiency.

Source: Chisti, 2007.
bon sugars and the fermentation of sugars to ethanol. This remains a technical challenge due to the nature of lignocellulosic feedstocks; and
•     Improving fractionation technology while reducing the sulfuric acid and heat to hydrolyze lignocellulosics.

Research  options  for third generation  algal/cyanobacte-rial biofuels could focus on increasing organism survival, growth and lipid content, carbon dioxide enrichment and yields:
•     Organism survival: the best laboratory strains become contaminated and taken over by indigenous local or­ganisms under field conditions. Transgenes conferring herbicide resistance might overcome this problem;
•     Growth &   lipid content: algae either grow or alterna­tively they produce lipid (fat) bodies, but not do both simultaneously. This requires batch culture or separate growing ponds and lipid producing ponds, increasing production costs. Pathways and genes for continuous production of the best lipids for biodiesel are becoming known and could be explored (Ladygina et al., 2006);
•     Carbon dioxide enrichment: the algal response to added carbon dioxide is not as good as it could be; molecular research in photosynthesis could potentially increase yield (Ma et al., 2005);
•     Seasonal high yields: algal growth is a function of tem­perature—when it is too cold they grow less and most do not do well at high summer temperatures; recent and future AKST with plants will have much to offer to overcome this problem (Shlyk-Kerner et al., 2006); and
•     Poor  light  penetration to  cultures  requires  shallow ponds and lower yields; further research in trimming photosystem antennae size could greatly increase effi­ciency and yields (Tetali et al., 2006).

Research is also required to establish the ecobalance and life cycle analysis for each source.

Fourth generation: producing biohydrogen and bioelectricity
Biophysicists have seen it as an intellectual and practical challenge to harvest solar energy to produce hydrogen or electricity by directly using nature's photosynthetic mecha­nisms, or by embedding parts of the photosynthetic appara­tus in artificial membranes, or using algae to produce sugars and yeast or bacterial enzymes to produce electrochemical energy (Tsujimura et al., 2001; Chiao et al., 2006; Logan and Regan, 2006). This will necessitate considerable long term multidisciplinary efforts to become more than a labo­ratory curiosity. The informational gains, as well as the new fuel gains about basic biophysical processes are bound to be exceedingly important to AKST.

Biofuels and global carbon balance
The grains, oilseeds and specially cultivated grasses (switch-grass and Miscanthus) used for biofuels require consider­able fuel in their production and processing. The straws by-products require energy only in harvest and processing and will give a much more favorable carbon balance. Algae and cyanobacteria can achieve the highest carbon balance, as they can be directly "fertilized" by industrial flue gasses, directly removing them from the environment (Brown and Zeiler, 1993).

6.2.3.2 Improve energy efficiency of supply chains: food miles and life cycle analyses
Changes in food production and marketing systems, ac­companied by changes in transport technologies, have led to increased transportation of agricultural and food com­modities, both in raw and processed forms. Modern food supply chains, transforming goods from field to fork, tend to have greater "food miles" per unit of final consumption than in-season, locally procured items. Transportation en­ables producers to exploit comparative advantage in farm­ing and food by extending the spatial distribution and size of markets for their produce, to the mutual benefit of pro­ducers and consumers, thereby enhancing overall economic efficiency. This applies to produce transported within NAE and between NAE and other regions.
     High food miles, especially involving heavy road vehi­cles, can, however, have negative impacts on sustainability associated with energy use, congestion, pollution and ac­cidents (Smith et al., 2005). These transport related impacts can be significant at the local and national scales. Further­more, failure to fully attribute the costs of these impacts to transport could give unfair advantage to distant compared to local produce. A large share of total food miles, however, is attributable to shopping by car at out-of-town supermar­kets, reflecting changes in retailing and in purchasing habits (Pretty et al., 2005; Smith et al., 2005).
     Thus, the relationship between food miles and sustain­ability of food supply is complicated (Smith et al., 2005). Aggregate travel distance is not in itself a useful indicator. Shorter distances are not necessarily more sustainable due to differences in the characteristics of food and supply systems (Smith et al., 2005; Saunders et al., 2006). Much depends on modes of transport, economies of scale in transportation, complementary functions such as refrigeration and differences
in the overall cost and energy efficiency of food pro