Chemical feedstocks are beginning to move away from their heavy reliance on petroleum. Although the precise timing for this transition is open to much debate, the trend is inevitable.
Just six polymeric materials — high- and low-density polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyester (polyethylene terephthalate) — make up 76% of plastics produced. Mankind's appetite for these petroleum-derived products is not waning, although it is increasingly supplementing its diet with products from sustainable, bio-based feedstocks. Although a tipping point may be some way off, the amount of crude oil is finite, and renewable alternatives must eventually take over.
This transition can be exciting, because it involves more than just sourcing a renewable feedstock to replace a petroleum product. Indeed, the use of bio-based feedstocks gives rise to new chemical space, potentially offering cheap access to functional groups and building blocks that are more difficult to obtain from petroleum. Commercializing bio-based products can proceed along two different paths, each with its own risks and rewards.
The first and most common approach involves using renewable chemicals as direct replacements for existing products, for which markets are established and (largely) predictable. Developing replacement chemicals is extremely challenging, and their adoption can be stifled by even minor differences from the presently used material. The sheer number of initial experiments run, meetings held and pilot plant trials conducted represents a very real barrier to renewables finding their place in industry. On top of this, yet more meetings and experimentation may be required, after which approval from management is still not guaranteed. Moreover, if the material is to be used in a highly regulated environment — such as medical devices or aerospace — then government approval may also be necessary.
The closer the new material is to the existing material, the more it can be considered a ‘drop-in replacement’. A true drop-in replacement, indistinguishable from the existing material, would require no change in machine settings, quality control standards or other special treatment. This would be a dream material. But it is this dream of a perfect drop-in replacement that drives much of the industrial research on bio-based feedstocks. Examples of this approach include renewable replacements for petroleum-derived polyethylene, which, as the largest volume plastic in the world, is a tempting target. The production volumes are immense, such that making even a small fraction of it from renewable resources could be financially rewarding.
One true drop-in replacement would be bio-based ethylene monomer, which is produced by dehydration of ethanol, itself the product of sugar fermentation. Other than 14C isotopic differences, bio-based ethylene is identical to petroleum-based ethylene. Not a dial or knob on any factory's control board needs to be adjusted regardless of whether the monomer came 6,000 metres from under the ground or from an adjacent farm.
Instead of exploring novel chemistry and the new polymers that may be produced, much effort is being focused on recreating bio-based versions of petroleum-based feedstocks. A largely overlooked factor motivating this effort is the tremendous amount of manpower and capital industry has already spent on the production of ultra-efficient factories to produce the ‘Big 6’ polymers. Such infrastructure is not easily or cheaply altered to handle non-traditional feedstocks, and there is strong incentive to maximize the return on investment. The production efficiencies, optimized over many years, are such that product prices can be low and yet production profitable despite razor-thin margins. The chief technology officer of Proctor & Gamble recently stated that the company is “highly interested in finding bio-based routes to [incumbent] commodity plastics which fit with current processing and disposal infrastructures,” but is “less concerned with developing new-to-the-world biodegradable plastics for [their] packaging and products.” (ACS Macro Lett. 2, 550–554; 2013). Thus, although developing renewable methods to commodity plastics may seem appealing because of the sheer size of their market, supporters of novel feedstocks will probably not have the capital resources needed to compete with existing infrastructure.
There is a second, alternative approach for the introduction of bio-based feedstocks. I learned very early on in my industrial research career — admittedly through a crash course (or two) in the school of hard knocks — that a more practical route to introducing new materials is to seek out new applications. In a new application, new materials are able to compete on a level playing field with existing materials. There is no inside track for the incumbent.
This method is not without its own risks. Instead of being able to fulfill existing large-volume orders for commodity items, time and effort needs to be spent on creating a new product, with the hope that it can be successfully sold. Such a process often involves interacting with hundreds (or thousands!) of customers, and requires time and money.
Overnight sensations that take the world by storm are rare; building a new market one customer at a time is far more common. All in all, none of this happens quickly or cheaply (and seldom in the linear manner that was desired).
There are, then, two paths with two different sets of risks and potential outcomes. In the replacement strategy, the risks are minimal on the sales and marketing side because the market already exists. However, the risk that the new chemicals and materials will fail to meet all of the technical requirements is great. When the adopted strategy is that in which new applications are sought, the risks are reversed. New materials used in judiciously designed new products will face the dire possibility of never being accepted and purchased by businesses and consumers.
All of this means that the shift to bio-based feedstocks and their respective product materials will be a slow evolution rather than a rapid revolution.
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