generation biofuels). The possibility of producing biohydro-gen and bioelectricity using nature's photosynthetic mechanisms (4th generation biofuels) might be explored as well.
Ethical considerations—effects on food security
The rapid growth of biofuels industry is likely to keep farm commodity prices high through the next decade as demand rises for grains, oilseeds and sugar from 2007 to at least 2016 (OECD/FAO, 2007). This will substantially increase meat and milk prices in the NAE and decrease the amount of grain available to the poorer parts of the world both as direct imports and food aid. Brazil's earlier diversion of cane sugar to ethanol stabilized high sugar prices, assisting farmers worldwide, but at a higher consumer price. The diversion of grain to fuel can negatively affect the millennium goal of alleviating hunger throughout the world in the short term, but might have a positive long-term effect. Because heavily subsidized NAE grain will no longer be "dumped" on developing world markets below production costs, the subsistence farmers in the developing world could switch from subsistence to production agriculture, increasing yields and self-sufficiency. There are also eco-ethical considerations; putting more ecologically fragile and necessary lands into production of biofuels; whether oil palm production in Southeast Asia at the expense of jungles, or soybean production at the expense of rangeland or rain forest. It may not be morally justifiable to purchase oils for biofuels from areas where the environment is being negatively exploited. Proponents of some biofuel crops state that they will be grown on "marginal" land. Such lands may not be marginal to biodiversity and wildlife, posing another ethical issue. As discussed below, a major NAE biofuel crop, oilseed rape emits a major greenhouse gas and Jatropha, which is promoted by many NAE organizations in Africa and Asia is highly poisonous. There are ethical issues about promoting the cultivation of such crops. Thus alternative feedstocks that do not increase agricultural area are needed for biofuel production, such as waste cellulosic material, algae and cyanobacteria.
First generation biofuels (cereal grains and oilseeds)
The energy, economic and environmental results of the 1st generation liquid biofuels cannot make them a substantial alternative to fossil transport fuels (IEA, 2004; Sourie et al., 2005). Co-production can improve energy and economic balance and biofuel costs will go down as the technologies improve in production efficiency and economies of scale are realized (Farell et al., 2006). In addition, the amounts of land that would be required to obtain self-sufficiency in biodiesel using oilseed crops alone varies from 9-122% of the global cropping area (Table 6-1), which makes it clear that both fuel and food needs cannot be supplied by standard crop agriculture alone.
Second (cellulosic substrates) and third generation (algae and cyanobacteria) biofuels
New developments in biofuel production seem necessary. Two types of cellulosic second generation substrates for biofuel production are being considered: straws and specially cultivated material. The use of cellulosics will have a higher net energy gain than seed grains/oilseeds (Samson et al.,
2005; Farrell et al., 2006), but the present technologies are less environmentally friendly than those using grain, as they use dilute sulfuric acid and heat to separate lignin from the carbohydrates. Third generation sources, such as algae, may be even more environment friendly as well as cost effective. Concentrating future R&D options on the following areas can help make second and third generation sources viable:
Research can help define plant ideotypes that fulfill certain criteria and respond to certain needs:
• Assimilation of carbohydrates (starch and sucrose) at the detriment of proteins. This is cost effective as the crop requires a lower quantity of inputs (particularly water and nitrogen) and has less hauling requirements; some examples are leguminous plants, as they require less fertilizer and the cultivation of C4 plants adapted to low temperatures (Heaton et al., 2004);
• Production of fermentable 5- and 6-carbon sugars that can subsequently be converted to ethanol;
• Increasing the amount of cellulose (especially at the expense of lignin), or modifying its structure such that more is available to cellulases could increase the bio-ethanol yield of straws and specialty grasses, while lowering demands for acid and heat for hydrolysis (Attieh et al., 2002);
• Increasing the lignin content and the digestibility of straws through transgenics. The solution to increasing digestibility without affecting important traits is to transform elite material to contain modified lignin and cellulose contents, e.g., by partial silencing of the pathway enzymes leading to lignin (Gressel and Zilberstein, 2003), or by enhancing cellulose synthesis (Shani et al., 1999);
• Lowering the presence of polluting silicon in both straws and cultivated grasses;
• Lowering emissions of methyl bromide from oilseed rape or canola (Gan et al., 1998);
• Developing lodging-tolerant varieties and when necessary dwarfed varieties;
• Developing insect resistant varieties, as lower lignin can lead to pest infestation;
• Improving the stand establishment of perennial grasses (Schmer et al., 2006);
• Compensating for the reduction of soil carbon and its consequences on soil quality due to straw harvesting; and
• Explore the harvesting of unwanted aquatic weeds such as water hyacinth for biofuel production.
Biotechnologies including genetic engineering could potentially achieve most of the above mentioned targets by modifying certain metabolic pathways. Development of such modified varieties requires taking into account appropriate safety concerns.
Research and technological developments could focus on increasing processing efficiency by:
• Increasing the efficiency of cellulolytic enzymes, e.g., by gene shuffling to increase activity, stability, temperature optima;
• Improving the pretreatment step that disrupts the structure of the biomass and releases 5-carbon sugars from hemicellulose, hydrolysis of the cellulose to form 6-car-