Biomaterials: The Potential for Bio-Isoprene
4:38 AM MST | December 22, 2011 | By MARK MORGAN, MANAGING DIRECTOR/RENEWABLES, IHS CHEMICAL
A review of the market potential for bioisoprene, with analysis of the key technologies and companies seeking to introduce those technologies to the market.
Isoprene is a very versatile petrochemical building block mainly used in synthetic rubber and thermoplastic elastomer production. A small amount of isoprene is also used in the synthesis of fine chemicals such as flavor and fragrance intermediates.
Global demand amounts to around 770,000 m.t./year. While the former Soviet Union (FSU) still dominates global isoprene demand, future growth is strongest in developing economies like China and Latin America. Overall global growth is in line with or slightly less than average GDP.
However, growth is limited by supply. The movement of the U.S. stream cracker feedslate to NGLs, driven by competitive shale gas supply, is impacting the contained isoprene availability in North America.
Current Isoprene Technology
A major proportion of the world’s isoprene is made via separation from the petrochemical C5 stream. C5 components are found in pyrolysis gasoline. However, in order to exact isoprene a complex series of separations are needed to remove first cyclopentadiene as its dimer-DCPD, as well as piperylene, culminating in extractive distillation for isoprene recovery. For a 1 million m.t./year high severity naphtha cracker, around 20,000 m.t. of contained isoprene are co-produced. Accessing isoprene is very capital intensive, but has the compensation of valuable co-products.
In the FSU, where there is access to competitive NGL sources, deep isopentane dehydrogenation is still used for isoprene manufacture. Production this way dates back to the COMECON era, as does the FSU’s use of the isobutylene/formaldehyde process. The latter is also operated by Kuraray.
Acetylene has also been used to make isoprene, such as by Karbochem in South Africa in the 1980s, and Enichem at Ravenna, Italy. The continued development of coal-based chemicals in China, suggests this approach could be revisited.
Isoprene is expensive to produce and so one of the drivers in developing bio-based isoprene, is the ability to exploit low cost sugars derived from biomass as well as provide a green starting material for products like styrene block copolymers for use as adhesive and other applications.
The economics of isoprene production are linked to naphtha and premium gasoline as well as overall energy costs. Given increases in crude oil price during the past decade, there is a strong economic driver for isoprene production from renewable resources provided feedstock costs allow the process to remain competitive.
Green Isoprene Technology Overview
With this approach, glucose sourced from biomass, is converted to isoprene via microbial strain development. To the knowledge of IHS, this process is not yet implemented on an industrial scale. Companies such as Genencor/Goodyear, Amyris and Glycos Biotechnologies are on the forefront of this process technology development at this time.
The biotransformation process requires microbial strain development to provide a microorganism with sufficient capabilities to support the fermentation of glucose - possibly sucrose and other sugars - from renewable resources into isoprene. The bio-derived isoprene generated needs to be recovered and purified to a specification suitable for high cis polyisoprene where the specification is tightest. As with butadiene, isoprene is reactive and requires stabilization with an inhibitor, such as tertiary-butyl-catechol.
IHS is of the view that the Genencor process for bio-based isoprene is revolutionary. The company, collaborating with Goodyear, is looking seriously at commercialization within the next few years. Amyris in its collaboration with Michelin is looking to do likewise. Glycos Biotechnologies, through its collaboration with BioXcell in Malaysia is looking to provide commercial bio-based isoprene supplies to the market in 2013. Tires manufactured using green isoprene have already been demonstrated, such as by Goodyear. Goodyear as a major producer of isoprene and polyisoprene, based in North America is wise to seek alternative isoprene supply given the projected impact of shale gas on the region’s cracker feedslate and hence the potential reduction in contained isoprene supply. The impact already has been noted by IHS. Access to green isoprene could also reduce the carbon footprint of certain isoprene consumers, not only Goodyear, but also Kraton Polymers, a major prodders or SBCs.
The key to Genencor’s technology is that it consists of a process that engineers a microbial cell culture that drives sugar conversion through engineered biosynthetic pathways, to produce isoprene at very high yields through an aerobic biotransformation. Pathways that drive the reaction away from isoprene are attenuated and those that drive the reaction toward isoprene production are enhanced. With a boiling point of 34°C, isoprene is very volatile and can be removed from the fermentation broth with relative ease such that it does not accumulate as a poison for the microorganism that makes it. However, isoprene makes explosive mixtures with air when in a 2%-9% concentration so care is required to ensure that the air feed to the fermentation ensures all oxygen is converted, leaving isoprene to vaporize into an atmosphere of carbon dioxide and nitrogen. This challenge was one of the reasons the Genecor development program was temporarily suspended in 2011. However, IHS understands that the program has restarted, moving to pilot scale, on the assumption that key development milestones have been met.
Companies developing bio-based isoprene processes have altered a number of the enzymes in the biosynthetic pathway to increase both the rate of production and the overall yield of isoprene. Technological developments have featured changes to media, substrates, specific primers, enzymatic pathways and more. These novel ideas have improved the efficiency and quantity of isoprene produced with a concomitant decrease in the production of by-products.
There are two metabolic pathways, namely via mevalonic acid (MVA) and 5-methyl erythritol phosphate (MEP). Under its Process Economics Programme (PEP) business line, IHS recently completed and published its review entitled ‘Bio-Based Isoprene’ based on public domain information (patents, literature, industry interviews, and more), plus in-house expertise and engineering judgement, IHS has developed its view of process biochemisty, process design through process simulation, mass balance, detailed capital and operating cost estimates, and more for a glucose-fed, U.S.-based facility with a capacity of 100,000 m.t./year.
At this stage, based on a variable glucose price, the economics of green isoprene look encouraging, but glucose cost dominates the techno-economic view of the process. Hence there is a continued need to exploit other C6 sugars, possibly those derived from cellulosic biomass.
by Mark Morgan, Global MD Renewables, IHS Chemical
Mark.Morgan@ihs.com, tel: +44 (0) 794 056 0911)
Bio-based Isoprene PEP Review Author, Sudeep Vaswani (Senior Analyst, IHS, email: Sudeep.Vaswani@ihs.com)