Given the current robust forces driving sustainable production, and available biomass conversion technologies, biomass-based routes are expected to make a signifi cant impact on the production of bulk chemicals within 10 years, and a huge impact within 20-30 years. In the Port of Rotterdam there is a clear shortterm (0-10 year) substitution potential of 10-15 % of fossil oil-based bulk chemicals by bio-based bulk chemicals, especially for oxygenated bulk chemicals, such as ethylene glycol and propylene glycol, iso-propanol and acetone, butylene and methylethylketone and for the replacement of methyl tertiary butyl ether (MTBE) by ethyl tertiary butyl ether (ETBE). Glycerin, as a byproduct of biodiesel production, is a very favorable short-term option for the production of ethylene and propy lene glycols in the Port of Rotterdam. In the mid-term (10-20 years) there is clear potential for a bio-based production of ethylene, acrylic acid and N-containing bulk chemicals such as acrylonitrile, acrylamide and ε-caprolactam. Technologies involving direct isolation of aromatic building blocks from biomass, or the conversion of sugars or lignin to aromatics are still in their infancy. Biorefi neries that are being started up today will form the stepping stones toward the chemicals mentioned above if we learn to upgrade their side streams. For main ports like the Port of Rotterdam, these developments imply that it has to consider in much closer detail those facilities it has to offer for a more bio-based chemistry and economy.

The depletion in fossil feedstocks, increasing oil prices, and the ecological problems associated with CO 2

This paper describes several examples of knowledge-intensive technologies for the production of chemicals from biomass, which take advantage of the biomass structure in a more efficient way than the production of fuels or electricity alone. The depletion in fossil feedstocks, increasing oil prices, and the ecological problems associated with CO(2) emissions are forcing the development of alternative resources for energy, transport fuels, and chemicals, such as the replacement of fossil resources with CO(2) neutral biomass. Allied with this is the conversion of crude oil products utilizes primary products (ethylene, etc.) and their conversion into either materials or (functional) chemicals with the aid of co-reagents such as ammonia, by various process steps to introduce functionalities such as -NH(2) into the simple structures of the primary products. Conversely, many products found in biomass often contain functionalities. Therefore, it is attractive to exploit this in order to by-pass the use, and preparation of, co-reagents as well as to eliminate various process steps by utilizing suitable biomass-based precursors for the production of chemicals.

Oils, fats, carbohydrates, lignin, and amino acids are all important raw materials for the production of biorenewables. These compounds already play an important role in everyday life in the form of wood, fabrics, starch, paper and rubber. Enzymatic reactions do, in principle, allow the transformation of these raw materials into biorenewables under mild and sustainable conditions. There are a few examples of processes using immobilised enzymes that are already applied on an industrial scale, such as the production of High-Fructose Corn Syrup, but these are still rather rare. Fortunately, there is a rapid expansion in the research efforts that try to improve this, driven by a combination of economic and ecological reasons. This review focusses on those efforts, by looking at attempts to use fatty acids, carbohydrates, proteins and lignin (and their building blocks), as substrates in the synthesis of biorenewables using immobilised enzymes. Therefore, many examples (390 references) from the recent literature are discussed, in which we look both at the specific reactions as well as to the methods of immobilisation of the enzymes, as the latter are shown to be a crucial factor with respect to stability and reuse. The applications of the renewables produced in this way range from building blocks for the pharmaceutical and polymer industry, transport fuels, to additives for the food industry. A critical evaluation of the relevant factors that need to be improved for large-scale use of these examples is presented in the outlook of this review.

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Use of biomass is crucial for a sustainable supply of chemicals and fuels for future generations. Compared to fossil feedstocks, biomass is more functionalized and requires defunctionalisation to make it suitable for use. Deoxygenation is an important method of defunctionalisation. While thermal deoxygenation is possible, high energy input and lower reaction selectivity makes it less suitable for producing the desired chemicals and fuels. Catalytic deoxygenation is more successful by lowering the activation energy of the reaction, and when designed correctly, is more selective. Catalytic deoxygenation can be performed in various ways. Here we focus on decarboxylation and decarbonylation. There are several classes of catalysts: heterogeneous, homogeneous, bio-and organocatalysts and all have limitations. Homogeneous catalysts generally have superior selectivity and specificity but separation from the reaction is cumbersome. Heterogeneous catalysts are more readily isolated and can be utilised at high temperatures, however they have lower selectivity in complex reaction mixtures. While bio-catalysts can operate at ambient temperatures, the volumetric productivity is lower. Therefore it is not always apparent in advance which catalyst is the most suitable in terms of conversion and selectivity under optimal process conditions. Here we compare classes of catalysts for the decarboxylation and decarbonylation of biobased molecules and discuss their limitations and advantages. We mainly focus on the activity of the catalysts and find there is a strong correlation between specific activity (turn over frequency) and temperature for metal based catalysts (homogeneous or heterogeneous). Thus one is not more active than the other at the same temperature. Alternatively, enzymes have a higher turnover frequency but drawbacks (low volumetric productivity) should be overcome.