As observed, the production of the US and Brazil combined covers almost 90 per cent of the world production of biofuels. In 2006, the US produced 18.4 billion litres (46 per cent of the world’s total) and Brazil 16 billion litres of ethanol (42 per cent of the world’s total; World Bank, 2008).
Even though this still does not represent a large-scale production at world level (in 2005, ethanol comprised only 1.2 per cent of the world’s liquid fuel supply), it is large enough to allow an assessment of the technological coefficients from the analysis of aggregated values referring to the whole sector. This method is much more robust than inferring aggregate values from measurements taken at the level of individual plants, a method which implies a risky scaling-up.
The total output and total labor demand of ethanol production, both in the US and Brazil, used in the following assessment is based on data provided by the ethanol industry for the whole sector. Using these data we assessed the external and internal constraints.
In relation to internal constraints, we focus here only on the requirement of labour in the energy sector by using an evaluation of the EMRAB, the power level of exosomatic energy consumed per worker in the agro-biofuel production process.
This evaluation depends on the output/input ratio, since the energy consumed in the process of generating GSEC coincides with the input of energy carriers (GSEC -> NSEC) that has to be consumed in order to generate NSEC. The power level is calculated by dividing GSEC -> NSEC by the hours of work in the process.
Finally, in this assessment we used the output/input calculated by Farrell et al (2006) for ethanol from corn in the US, but corrected the value by eliminating the energy credits for by-products. In fact, even at a 3 per cent substitution of liquid fuel with the net production of ethanol – fully renewable and with zero emissions the displacement method is not justified.