Overview

Biomass resources, which could be used as renewable carbon sources in the chemical industry, are for the most part used for food and feed. Plant derived and refined starch, sugar, and oils/fats account for the biggest volumes and will therefore be considered in more detail. In terms of CO2 reduction, however, a closer look has to be given to the use of plant residues and thus biomass as a whole.

In 2007, about 7% of all chemical sales were generated using bio - based feedstock, biotechnological production methods or a combination of the two. Products include pharmaceutical ingredients, enzymes, ethanol, oleochemicals and food and feed ingredients [3]. For the German chemical industry for example, fats and oils are the most important renewable feedstocks with about half of the total of 2.7Mtons of renewable raw materials used, followed by starch (23%), cellulose (12%) and sugar (11%) [4]. More than a third of these triglycerides are used tenside production - not only to make cleaning detergents but also for the pharma-, cosmetic- and textile industry. Also lubricants, polymers and polymer additives as well as lacquers and colorants are important branches using these raw materials. Fats for the chemical processing are mainly derived from animals (e.g., milk or tallow), from plants (e.g., palm oils or seed oils), and from microorganisms (e.g., algae).

Sugar (esp. glucose) is mainly used for the production of ethanol. Complex carbohydrates such as starch and cellulose can also be used as a glucose source. The main sources of starch are maize (corn), potatoes, wheat, tapioca (cassava), rice, arrowroot and barley. Starch as well as sugar (here sucrose) is used mainly in the ethanol production, but also in the fermentation of organic acids (such as citric and lactic acids), amino acids, and antibiotics. Some of the other technical applications include biodegradable plastics (polylactic acid (PLA)) for the packaging and textile industries, surfactants, polyurethane, resins, binders, solvents, biopesticides and lubricants. On the other hand cellulose is mainly separated, along with lignin and proteins, from plants and biomass residues, such as wood or straw. In contrast to starch, the fermentation of cellulose with current enzymes is relatively slow and inefficient. Harsher environments as well as more complex and capital intensive enabling technologies are therefore necessary, leading to a relatively high cost constraint with current techniques.

Regarding CO2 emissions from various biomass sources, Figure 12.1 compares total emission data from crop cultivation and acquisition for the entire biomass material. Best practice yield values (between 2005-2008) in large producer countries (see brackets) were selected. Palm oil, sorghum, cassava and sugar cane have a level of associated emission from transportation but their high yields result in relatively low emissions per material feedstock. On the basis of common expert opinion, the lowest relative feedstock- based CO2 emission is held by the high-

Figure 12.1 Carbon dioxide emission vs. biomass dry weight for regional half-products [5].

yielding Brazilian sugar cane, whereas sunflower with its low biomass yield results in the highest relative emissions.

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