First-generation feedstocks

Starch- and sugar-containing crops are quantitatively the most important products of today s agricultural system. Most of the existing biorefinery concepts are based on these plants and they are referred to as first-generation feedstock (vide supra), but they also constitute the backbone of human nutrition. General characteristics of this type of biorefinery are listed in Table 1.1. 

The simple scale up of the current bio-based plastics production technologies usually utilize first-generation feedstock, such as sugarcane or com, which are likely to increase the competition of the production of food and bio-based chemicals. 

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. 

Burdett, K.A., L.D. Harris, P. Margl, B.R. Maughon, T. Mokhtar-Zadeh, P.C. Saucier and E.P. Wasserman, Renewable Monomer Feedstocks Via Olefin Metathesis Fundamental Mechanistic Studies of Methyl Oleate Ethenolysis with the First-Generation Grubbs Catalyst, Organometallics, 23, 2027-2047 (2004). 

Naturally-occurring fatty acids, such as oleic acid, could serve as feedstocks for metathesis-centered transformations. For example, workers at Dow Chemical Company explored the use of Grubbs first-generation catalyst (23) to promote ethenolysis of methyl oleate (equation 11.18) to form C10 alkenes, which might serve as feedstocks for some of the processes that have already been mentioned in this section.49... 

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. 

Each of the described collection and sorting methods have inherent strengths and weaknesses. They will most likely have to be used in combination to achieve good sorting. It remains to be seen whether the economy and energy efficiency of such systems will be competitive compared to incineration or landfill. As will be seen, the efficiency of this first step of plastics recovery determines not only the way the material will be recycled but also the applications for the generated feedstock. 

Shaw selected a combination of polyolefin resins from Dow Chemical as the base polymer of choice for EcoWorx due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled. The EcoWorx compound also had to be designed to be compatible with nylon carpet fiber. Although EcoWorx may be recovered from any fiber type, compatibility with nylon-6 provides a significant advantage. Polyolefins in EcoWorx are compatible with known nylon-6 depolymerization methods, whereas PVC interferes with those processes. Nylon-6 chemistry is well known and not addressed in first-generation production. 

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