Second generation feedstocks

As crop residues are by-products of food production they are termed as so-called second-generation feedstock, especially for biofuels production (see e.g., [35]). So far, no world market for straw aimed at industrial applications exists. However, prices can be approximated by calculating production and logistics costs [36]. 

Table 5.6 Second-generation feedstocks as possible raw material for the production of bulk chemicals and bioethanol (based on Antzar-Ladislao, Turrion-Comez [19]).

Table 13.1 indicates the advantages and disadvantages for different feedstock options for bio-based plastics. It shows that there is no easy answer to the question of whether second-generation feedstock really is a better solution for the production of bio-based products. The answer depends on the criteria one is looking for. 

The production of biofuel from edible oils (first generation of biodiesel) has increased many environmental issues such as competition over land usage for crops agricultural and biofuel production. In conjunction with this, food shortage, raised food prices, and destruction of biodiversity as deforestation occurred (Lin et al., 2011) are major causes for concern. The production of biodiesel from second-generation feedstocks should be encouraged to make these more viable/profitable and will be discussed in depth in Section 6.2.3.1. 

In summary, these second-generation gasifiers offer promise for the future in terms of increased efficiency as weU as for use of other feedstocks, such as biomass. The older, first-generation gasifiers, however, continue to be used. 

Second-generation biofuel technologies make use of a much wider range of biomass feedstock (e.g., forest residues, biomass waste, wood, woodchips, grasses and short rotation crops, etc.) for the production of ethanol biofuels based on the fermentation of lignocellulosic material, while other routes include thermo-chemical processes such as biomass gasification followed by a transformation from gas to liquid (e.g., synthesis) to obtain synthetic fuels similar to diesel. The conversion processes for these routes have been available for decades, but none of them have yet reached a high scale commercial level. 

The same holds true for hydrogen however, biomass yields more kilometres when used via hydrogen in fuel-cell cars than liquid biofuels in ICE cars (see Fig. 7.5). Moreover, as hydrogen is produced via gasification, it is equivalent to second-generation biofuels, as it can use feedstock that does not interfere with the food chain. 

The development of second-generation biofuels may however require more patience. Some of the most popular biocrop feedstocks seem to belong to what are called "invasive species," better known as "weeds," with a high tendency to escape biofuel plantations and overrun adjacent farms and natural land [66]. One expert stated that investors have often started these new ventures in the expectation to produce biofuels in return and in the not-too-far future. It is understandable that they do not like negative assessments. But clearly this is another example where a proper assessment has to be made and patience needs to be applied. 

It was observed that Pt/HZSM-5 was of higher catalytic activity than commercial C0M0/AI2O3 in the hydrodesulfurization of thiophene. Therefore, there is a possibility for using Pt/HZSM-5 as highly active, second generation hydrodesulfurization catalyst for petroleum feedstocks. 

It is evident that 0.5wt%Na-5wt%Rh/USY catalyst shows higher and more stable catalytic activity for the hydrodesulfurization of thiophene than 5wt% Rh/USY and C0M0/AI2O3 catalysts. Therefore, it can be concluded that there is a possibility of usage of Na- Rh/USY as highly active second generation hydrodesulfurization catalyst for petroleum feedstocks. 

Biofuels can be classified as first generation when they are produced from fermentation of sugar-based raw materials, second generation if they are produced from feedstocks such as lignocellulose and municipal solid wastes, and third generation when they are formed from algal biomass [314,315]. Currently, the most used biofuels are ethanol and butanol. 

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