countries such as Argentina, Brazil, Mexico, Uruguay and Colombia produce agrofuels mainly from sugarcane and oil palm. Brazil has produced fuel alcohol since 1975; it is the leading producer of sugarcane worldwide and produces 60% of the world total of ethanol from sugar, with three million ha of sugarcane crops. In 2005, production reached a record 16.5 billion liters, two million of which were for export (Jason, 2004).
     Among the advantages attributed to agrofuels as an alternative to fossil fuels that they mitigate climate change due to the reduction in gas emissions from the greenhouse effect, bring higher rural incomes for farmers and contribute to greater rural development. In Colombia, moreover, the government (in 2007) considers them an alternative to illicit crops and as a source of employment in rural areas.
     Most oil-dependent countries are engaged in the discussion of biofuels today, seeing in them a viable long-term solution to the problem of regional energy insufficiency. On the other hand researchers put forth concerns because they consider large-scale production of monoculture crops for agrofuels—under the conventional/productivist system of production dependent on chemical inputs (pesticides and fertilizer) made using the fossil energy that is sought to be replaced—will have negative impacts.
     The concerns are related to accelerated processes of deforestation, destruction of biodiversity, soil erosion and degradation, impacts on water and a negative balance of greenhouse gas emissions. To this situation are added the possible effects of displacement of food crops and increases in food prices, which will directly affect the food security and food sovereignty of local communities, mainly in developing countries. In Mexico, the redirection of maize crops for export to the United States to manufacture ethanol brought on a disproportionate increase in the price of maize, an essential ingredient in the tortilla, which is the main source of food and nutrition for the Mexican population. The increase in food prices is also hitting the livestock and poultry industries (Fearnside, 2001a; Bravo, 2006).
     RALLT (2004) cites studies that show that producing one tonne of cereals or vegetables with modern agriculture practices requires six to ten times more energy than using sustainable farming methods. The components of modern industrial agriculture that consume the most energy are the production of nitrogen fertilizers, agricultural machinery and irrigation using pumps. These accounted for more than 90% of the energy used directly or indirectly in agriculture and all are essential to it (RALLT, 2004). In addition, the elimination of carbon-sequestering forests to open the way to these crops will further increase CO2 emissions (Donald, 2004; Bravo, 2006).
     There is also a major debate on the energy balance for making ethanol or biodiesel from some bioenergy crops. The results of the research by David Pimentel and Tad Patzek at Cornell University in the United States (Pimentel and Patzek, 2005) support the notion that the energy balance of all the crops, with current processing methods, is such that more fossil energy is spent to produce biofuels than they provide. Thus, for each unit of energy expended on fossil fuel, the return is 0.778 units of methanol from maize; 0.688 units of ethanol from switchgrass; 0.636 units of ethanol from

wood; and, in the worst of the cases examined, 0.534 units of biodiesel from soybean (RALLT, 2004; Bravo, 2006).
1.6.2.3 Food chains
We understand agrifood chain to refer to the whole set of different movements in the process of food production that take place before, within and after agricultural production systems, linking all those involved, from the producer of inputs to the end consumer. The concept includes items whose end use is food as well as agricultural output sold to other industries. The set of all the agrifood chains, including support services, constitutes the agribusiness (Castro et al., 2001). The predominant model of development in the last 50 years, as already indicated, accorded priority to articulating the production systems and inputs and offered incentives for developing agroexports. The best-articulated agrifood chains in the region are for oil-bearing crops, beef, dairy products and vegetables. The opening up of Latin American markets and the need for the markets of the developed countries to expand has accelerated the economic concentration of the components of agribusiness, especially the supply of inputs and seed and marketing agrifood products, in which the multinational corporations are already the most powerful economic actors, influencing policy decisions that are restructuring agriculture generally, agrifood systems in particular and the process of technological development and technological innovations for the agricultural sector (Friedland et al., 1991; Bonanno et al., 1994; McMichael, 1994).
     Although the agricultural inputs sector was already dominated by large corporations before the 1990s, that decade saw a greater rate of concentration in this sector. For example, today only 10 corporations control 84% of pesticide sales in the world. The 10 largest corporations in the seed business control 50% of seed sales worldwide and the 10 largest biotechnology companies control almost 75% of biotechnology sales, including seed for transgenic crops (ETC, 2005).
     At the other end of the food chains one finds the processors, distributors and supermarkets. The penetration of transnational corporations in this sector is also proceeding by leaps and bounds in the region, even in rural areas. For example, in Argentina only seven supermarket chains control 77.5% of supermarket sales in 1999 and of these, 80% belonged to multinational chains (Carrefour, Ahold and
Wal-Mart, among others). As of that date, only two national chains had survived (Gutman, 2002). In Costa Rica, supermarket chains control 50% of all food sales and the seven largest companies control 98% of supermarket sales (Alvarado and Charmel, 2002). In Chile, four companies (two national and two foreign) control 50% of the market; the milk and dairy products sector is the most heavily dominated by the supermarket chains: the five largest companies account for 80% of sales (Faiguenbaum et al., 2002). The growing control of multinational chains in the sale of foods is taking place throughout the region. As of 2003 supermarket chains controlled from 50 to 60% of all food sales in LAC, an extraordinary increase, considering that just 10 years ago they controlled 10 to 20%. Five corporations control 65% of these sales (Reardon et al., 2003).
     This rapid growth and consolidation of supermarkets