In fossil refinery, succinic acid is currently produced from butane/butadiene via maleic acid and has a production volume of 30-50 kilotons/year (Bos et al., 2010). This process is relatively expensive and the existing market for succinic acid is limited. However, if a more economic production route could be established, it has a potential market of hundreds to thousands tons, thanks to its many possible derivatives (Sauer et al., 2008). Succinic acid can be efficiently produced from fermentation of sugars, on condition that low-cost fermen­tation routes are established. The basic chemistry of succinic acid is similar to that of the petrochemically derived maleic acid/anhydride. These compounds can be converted via hydrogenation/reduction to butanediol, tetrahydrofuran, and gamma-butyrolactone.

In the case of succinic acid, the technical challenge is the development of catalysts that would not be affected by impurities in the fermentation. Noteworthy is the possibility to produce pyrrolidinones, so addressing a large solvent market (Werpy and Petersen, 2004).

6.2.4 C5 Bulk Chemicals

Furfural is the starting material for industrial production of furan compounds and today it is completely produced from biomass feedstocks rich in C5 sugars. The market volume is

0. 2-0.3 million ton/year. It is obtained from hydrolysis of C5 sugars along with other degra­dation products. Removal of these impurities is expensive and industrial uses of furfural will benefit of an optimization of the furfural production process (Patel, 2006). Many valuable chemicals can be derived from furfural (e. g., maleic anhydride, furfuryl alcohol, etc.), and the chemistry for the conversions is well developed (Kamm et al., 2006b).

Itaconic acid has a chemistry similar to the fossil-derived chemicals maleic acid and maleic anhydride, which are used as monomers in the production of acrylate-based polymers and thermoset resins in oil refinery (Bos et al., 2010). Itaconic acid is currently produced via fungal fermentation and is used primarily as a specialty monomer. The major applications include the use as a copolymer with acrylic acid and in styrene-butadiene systems. The major techni­cal hurdles for the development of itaconic acid as a bulk chemical include the development of very low-cost fermentation routes. The primary elements of improved fermentation include increasing the fermentation rate, improving the final titer, and potentially increasing the yield from sugar. Besides important chemical derivatives, itaconic acid can also undergo polymerization, but the properties of polyitaconic polymers need to be ascertained in order to evaluate its use as a polymer (Werpy and Petersen, 2004).

Xylitol is commercially produced from hydrogenation of xylose, the most abundant C5 sugar in hemicellulose. At the moment, there is limited commercial production of xylitol, but once a cheaper production route is established a large potential for production of ethylene glycol and 1,2-propanediol via hydrogenation is expected.

Another promising C5 bulk chemical is LA. It is produced from dehydration by means of acid treatment of C6 sugars like glucose and fructose. LA is one of the most important build­ing blocks available from carbohydrates and has attracted interest from a number of large chemical industry firms: it has frequently been suggested as a starting material for a wide number of compounds (Bozell et al., 2000; Hayes et al., 2006; Kamm et al., 2006b; Werpy and Petersen, 2004). The technical barriers for this option include improvement of the process for LA production itself, even if the LA yield is already at 70% (Hayes et al., 2006). The family of chemical compounds available from LA is quite broad, and addresses a number of large volume chemical markets. Besides chemicals, LA shows promising efficiency in the conver­sion to methyltetrahydrofuran and ethyl levulinate, two fuel additives which can be blended up to 20% with gasoline and diesel (without requiring any modification of the engine).