Bio-Based Chemicals - As raw materials become increasingly scarce and expensive and the effects of global warming become progressively evident, the scientific, business and government communities along with society at large are developing strategies aimed at a structural transition from the fossil-based economy to the bio-based economy. Chemical production is no exception. Although only about 8% of total oil production output is supplied to the chemical industry, increasing the proportion of renewables in the feedstock mix appears to have definite advantages.

The list of benefits includes a reduction in CO2 emissions from fossil sources, access to complex structures produced by natural synthesis and higher consumer acceptance of bio-based products. This of course assumes price competitiveness and a characteristics profile which is at least comparable, and that depends on high raw material and process efficiency. Examples include plastics, bio-based solvents, surfactants and lubricants where biodegradability and the avoidance of harmful emissions are primary considerations. REACH regulations could also lead to increased use of bio-based substances in the chemical industry.

Bio-based Polymers
According to information published by the trade association Plastics Europe, around 265 million MT of plastics were produced worldwide in 2010. That equates to 6 % of global oil consumption which was nearly 4 billion MT (BP Statistical Review of World Energy 2011). In contrast, only 0.7 million MT of bioplastics were produced during that year. Growth however has been forecasted to be enormous. According to current estimates presented by Hans-Josef Endres (University of Applied Sciences and Arts in Hannover, Germany) during a presentation in November 2011, the figure is now approaching 1.7 million MT which equates to an annual increase of 20 %.
Bioplastics are however a heterogeneous group which includes bio-based as well as fossil-based plastics as long as they are biodegradable. Traditional biodegradable plastics are made from the natural polymers cellulose and starch. Then in the 1990's, the thermoplastic polymer polyhydroxybutyrate (PHB), which is used by bacteria as energy storage, was placed on the market under the trade name Biopol. This was the first bio-polymer which was used as a compostable alternative to PE in packaging applications. In recent years however, the approach has been not to use biopolymers directly. Instead biotechnology or chemical techniques are employed to extract monomers from renewable feedstock to provide a basis for new (functional analogue) or traditional (structural analogue) polymers.
Currently the most popular functional analogue bio-based plastic is polylactic acid (PLA). PLA has properties similar to those of conventional mass-produced thermoplastics and can be processed on existing production lines. Because it is compostable, PLA has considerable potential for throw-away packaging such as beverage cups and plastic food packaging trays. One disadvantage of PLA is its low melting point which makes it unsuitable for items that are exposed to heat.
Biotechnology and chemical techniques are used in combination to make the lactide polyester. Sugar or starch is fermented to make lactic acid, and a chemical dimerization process is then used to produce lactide. Finally, ring-opening polymerization is performed on the lactide monomer.
Industrial production of PLA got underway in 1994. Worldwide production capacity exceeded 110,000 MT/a in 2010. Production plants are located in the US, the Netherlands and China, and additional production facilities are scheduled for construction in countries like Thailand. According to information provided by Hans-Josef Endres (Bioplastics and Biocomposites Institute at the University of Applied Sciences and Arts in Hannover, Germany), production capacity is expected to double by 2015. Although PLA has good biocompatibility because it is bio-based, development of recycling or composting infrastructure could drastically improve its biocompatibility. Intensive research is currently underway on how to do that. At the moment for logistical reasons, incineration is the only option.
An entirely different approach is used for the production of bio-based polyethylene (PE). PE is not biodegradable, but established recycling paths exist, at least in Europe. By making the platform chemical ethylene from renewables, the existing value-added chains starting from the production of different plastics and continuing right through to the end-of-life scenarios can be utilized.
In 2010, Braskem of Brazil launched production of a bio-based structural analog using bioethanol as the base. Two additional PE plants as well as production facilities for polypropylene and PVC have been announced with an expected completion date of 2015. PE production capacity will double. According to the World Bioplastics study published by the Freedonia Group in 2011, Brazil is expected to start production of fully bio-based PET on an industrial scale by the end of the decade.
The higher degree of functionalization (alcohol and acid groups) of bio-based monomers compared to fossil feedstock can be exploited in a variety of plastics applications. To cite some examples, bio-based dicarboxylic acids (succinic acid) and polyols (castor oil, 1,3-Propandiol) are used in bio-based polyesters. Polyols are also used in polyurethane. Dehydration of lactic acid produces acrylic acid, a monomer of polyacrylic acid. Other acrylate polymers can be made through esterification of acrylic acid with castor oil or epoxidized vegetable oils. Butadiene which is used in the production of synthetic rubber can be made from ethanol. Castor oil derivatives are used in polyamides.
Many of these examples involve fine chemicals currently sold in niche markets where special functionality provides a unique selling point which justifies the higher product price. These features may include biodegradability or surface-specific properties such as reduced foaming in beverage cups as in the case of PLA. Further market penetration depends not merely on production costs and availability. Complete recycling systems are also needed to ensure resource-efficient production (and use).

Bio-based Lubricants
According to information contained in the World Lubricants report published by the Freedonia Group in 2011, worldwide demand for lubricants was 36.7 million MT in 2010. That figure is expected to rise to around 42 million MT by 2015. The German Agency for Renewable Resources (FNR) reported that more than 1 million MT of lubricants are used in the country each year including 35,000 MT of biolubricants (3 %).
Biolubricants are not the same as bio-based lubricants. They include all lubricants that are readily biodegradable regardless of whether they are bio-based, mineral-based, made with recycled oil or synthetic. Because this terminology is used, bio-based lubricants are not listed separately. Price is (still) an impediment to widespread use of biolubricants which are 2 to 3 times more expensive than conventional lubricants according to a market study conducted by Global Industry Analysts.
In contrast to mineral-based lubricants, bio-based lubricants are generally made from vegetable oil. Depending on requirements, they are used either in their native state (natural ester) or they are chemically modified (synthetic ester). The range of applications for bio-based lubricants covers the entire spectrum of conventional lubricants including hydraulic oil, multi-function oil, engine and transmission oil, lube oil and grease and special oils. The European Committee for Standardization (CEN) recommends a biogenic content in excess of 25 % (CEN Technical Report 16227).
Because of their long service life, low toxicity and fast biodegradability, bio-based lubricants are particularly attractive for environmentally-sensitive applications. Off-shore wind power generation is a particular challenge.
Although work is still in the R&D phase, there are already indications that bio-based lubricants may be suitable for wind power applications. By nature, bio-based lubricants provide better lubrication than comparable mineral-based products. They contribute to improved system operation in a number of ways, and they have good handling characteristics and superior filterability. A new research project (Win Lub II) has been launched to assess the suitability and compatibility of bio-based lubricating grease and hydraulic oils at major component manufacturers under the direction of Fuchs Europe Schmierstoffe.

Bio-based Solvents
In a study carried out on behalf of the German Ministry of Economics and Technology (BMWi), the Fraunhofer Institute for Systems and Innovation Research (ISI) estimated that the global solvents market is in the region of 19.7 million MT per annum. At least 12.5 % of the total market volume could be produced from biomass, but the current figure is only 1.5 %. Solvents are fluids that are able to dissolve, dilute or extract other substances without changing the chemical composition of the substances or of the solvents themselves. Solvents belong to the aromatic and aliphatic hydrocarbon, alcohol, ketone, ester, ether, glycol ether and halogenated hydrocarbon groups.
Production of most solvents is based largely on fossil feedstock. Due to sustainability and environmental protection considerations, the spectrum is expected to shift towards bio-based solvents. The list of new bio-based solvents includes things like fatty acid methyl esters, which are also used in biodiesel, and esters of lactic acid with methanol (methyl lactate) or ethanol (ethyl lactate) as well as natural substances such as D-limonene which is obtained from the rind of citrus fruits.
Another trend is to replace conventional organic solvents with biogenic solvents. Conversion of bio-based succinic acid or furfural (a byproduct of the cellulose industry) to tetrahydrofuran (THF) is one example.

Bio-based Surfactants
Bio-based surfactants (surface-active molecules) are produced by microbial fermentation or enzyme-catalyzed reactions. According to ISI, worldwide production volumes are in the region of 17 million MT.
Surfactants normally contain both hydrophobic and hydrophilic groups. In the case of bio-based surfactants, at least one of these groups is made from renewable resources.
The bio-based hydrophobic group is usually made from coconut oil or palm kernel oil. A hydrophilic group is normally made from carbohydrates such as sorbitol, sucrose or glucose. The use of animal fat has significantly decreased.
In contrast, the market for bio-based surfactants is expanding. Due to their good biodegradability and low to zero toxicity, they are used in specific applications by the paint, cosmetic, textile, agricultural, food and pharmaceutical industries. The mining and ore processing industry uses them as an emulsifier to facilitate oil production and for biological cleanup of contaminated sites.

Outlook
Given the scenario described at the beginning of the article, bio-based products are clearly in the ascendency. The question is not whether the chemical industry will exploit a new resource base. It is only a question of when. Biological feedstock has been used for a long time to make surfactants, so the transition should be relatively easy assuming that adequate bio-based alternatives are available. In the plastics sector, it appears that eco criteria will not initially be the prime consideration in the search for bio-based alternatives. Instead, the feedstock will simply be substituted as is the case with PE and other plastics which are derived from ethylene. However, the availability of ethylene made from ethanol will be a limiting factor. 8.5 million MT of bioethanol would be needed just to supply a substitute for the 5 million MT of ethylene which are used each year in Germany. That is ten times the country's current production capacity.

This article is based on a trend report compiled by specialized international journalists on behalf of Dechema Gesellschaft für Chemische Technik und Biotechnologie (Society for Chemical Engineering and Biotechnology), a nonprofit scientific and technical society based in Frankfurt am Main, Germany.