The conversion of biomass to biofuel varies substantially. First-generation bioethanol is produced through conventional fermentation of starch in the feedstock to convert it into glucose, which is then hydrolysed with the help of enzymes (Naik et al. 2010). The rest of the plant, as mentioned previously, is not employed in the production of bioethanol. It is therefore discarded, or used elsewhere, such as for fertilizer or as fuel in stationary energy provision. As a result, a substantial amount of the energy associated with cultivating, harvesting and processing is lost, with concomitant impacts on the environment, especially when carbon-based energy sources contrib­ute the bulk of the energy inputs, as they normally do so at present (Van der Laaka et al. 2007). A relatively high level of inefficiency and an arguably poor allocation of energy resources throughout the production process are therefore observable here.

First-generation biodiesel is produced from lipids, such as animal fats and vegetable oils, being reacted with an aliphatic alcohol, most often methanol or alcohol, in the presence of a homogeneous or heterogeneous catalyst (Naik et al. 2010). This process is generally referred to as transesterification. Some of the major drawbacks of this process include inefficient extraction of oil from seed, poisonous methanol run-off, high-reaction parameters and the complicated purifi­cation process that requires vast quantities of freshwater, which becomes contami­nated by small quantities of biodiesel. This necessitates water treatment to prevent these impurities entering ecosystems (Parida et al. 2011).

Some of the problems discussed above, however, may be addressed in the future through improvements in biotechnology. For example, genetic manipulation, together with biotechnological developments and improved horticultural practices, has the potential to greatly increase the amount of fermentable starches, sugars and oil found in crops destined for biofuel production (McLaren 2005; Davis et al. 2008). The use of sugar cane for biomass in Brazil has already shown itself as a leading light in first — generation bioethanol production, especially given that the fibre of the plant itself is used to produce the energy needed to produce the bioethanol (Larson 2008).

Second-generation biofuels are produced in a more sustainable way. There are two types of processes used to generate these fuels. The first, sometimes referred to as biochemical, uses enzymes to convert plant cellulose into bioethanol (Foyle et al. 2006; von Blottnitz and Curran 2007), with cellulosic or lignocellulosic (if the biomass contains lignin or woody material) bioethanol being the result. The second process, which is thermo-chemical in nature, is generally known as anhy­drous pyrolysis. This involves the chemical decomposition of biomass by heating it in an anaerobic environment, or without any reagents, so as to convert the plant material into liquid bio-oil or syngas. Liquid bio-oil cannot be used in conven­tional internal combustion engines, although it can be combusted to produce elec­tricity for stationary energy requirements (Chiaramonti and Tondi 2003). By way of contrast, fuels for conventional transport applications, including combustion in turbines, can be synthesized from synthesis gas (syngas) by subjecting them to heat treatment in the presence of air (Eggert et al. 2011). This is not a new pro­cess, having existed for decades, such as the gasification of fossil fuels to produce Fischer-Tropsch diesel, which, like Fischer-Tropsch gasoline, can also be cre­ated from second-generation biomass conversion (Larson 2008). In all these cases, high pressure and temperature requirements necessitate considerable energy inputs (Ragauskas et al. 2006).

It is obvious that a production process that uses all or almost all of the bio­mass is much more environmentally advantageous compared with first-generation processes. Furthermore, the choice of biomass for lignocellulosic bioethanol is much wider, which should allow a better matching of crop to local climatic con­ditions. For example, various types of hardy grasses requiring minimal care, and thus reduced energy inputs, can be used to produce the feedstock. Short rota­tion crops emerge as particularly useful for this purpose, including woody plants such as coppiced willow and poplar. Agricultural waste, such as sawdust, wood — chips or bagasse produced from sugar production, also looms as a clear possibil­ity for bioethanol production (Wright 2006). With anhydrous pyrolysis, any kind of organic waste material can be used. At present, second-generation production processes more or less only exist on a test or commercial demonstration scale, with almost all the commercial biofuel currently being used coming from first — generation processes (Eisentraut 2010). Stephen et al. (2011, p. 160) cite “large technological risk, large capital cost (driven by economies-of-scale), and the poor predicted economic performance of biorefineries” as the main barriers to their commercial uptake.

Overall, there is substantial debate about whether the production and applica­tions of fertilizers, pesticides and herbicides, together with energy inputs into the cultivation, harvesting, transport and production processes relating to the biomass and resultant biofuels themselves, in effect cancels out much of the energy derived from combusting biofuels for mobility-related purposes (Patzek et al. 2005). This is particularly so with regard to first-generation processes involving the waste of significant parts of edible food crops. Whatever the case, as Charles et al. (2007, p. 5743) concluded, “earlier biofuels have proved, at best, to be only marginally more environmentally sustainable and less polluting than fossil fuels, especially when one factors in resource requirements, in addition to production and refining costs”. Of course, improvement can clearly be expected as biomass cultivation and biofuel production methods are optimized over time.