Biofuels and bio-based chemicals have been promoted as a potential solution for dependence on petroleum. They also have favorable greenhouse gas emissions compared to fossil fuels and petrochemicals because any carbon sourced from biomass can be directly traced to atmospheric CO2 via photosynthesis. Plus, the increased emphasis on lifecycle analysis for both economic and ecological factors has caused industry players to become familiar with the details of bio-feedstocks. The drumbeat for biofuels has thundered for some time now, but new analysis is showing that bio-based polymers could become the next big thing.
Global commodity polymer demand grew from 20002007. After a slight dip in recent years due to the economic downturn, consumption is expected to continue to grow for the next ten years (Fig. 1), providing an opportunity for bio-based polymers to enter the market and make a splash. This idea is put forth and explored in a new report from Nexant called, Plants to plastics: Can nature compete in commodity polymers?
Fig. 1. Global commodity polymers demand
Many producers, especially in high cost locations, have been looking for lower cost feedstocks in places like the Middle East, or are considering alternative feedstocks such as bio-based sources. With virtually all Middle East ethane allocations already apportioned for petrochemical projects, a portion of the next wave of new ethylene may well be from bio-based sources that can emerge from strong agricultural-based economies such as Brazil, the US or India.
As illustrated in Fig. 2, there are many conventional routes to polymers that can be integrated with bio-based feedstocks to either supplement or replace current petrochemical feedstocks. The report from Nexant compares technology, economics and potential markets for polymers produced via renewable sources versus petrochemical sources.
Fig. 2. Potential green integration into the polymer value chain.
Bio-ethanol dehydration to ethylene is a 40-year-old commercial technology available for license from companies in Sweden and the US. Bio-based green propylene and other green commodity polymers most often can be made by adapting conventional petrochemical routes like metathesis. Metathesis is a common process to react butylenes with ethylene to make propylene. Bio-propylene has a few alternative routes, including:
Bio-butanol dehydration to butylenes metathesized with bio-ethylene
Bio-ethylene dimerization to butylenes metathesized with bio-ethylene to make bio-propylene
Bio-based propane dehydrogenation
Fermentation to propanol followed by dehydration.
The three leading commodity polymers in the market (all grades of polyethylene, polypropylene and polyvinyl chloride) are highly relevant to large volume applications, and can all potentially be made by bio-based routes. That is, finished bio-polymers can potentially be made that will be indistinguishable from the best-performing conventional polymers, but with carbon content completely sourced from green plants or biomass.
The report also examines bio-based polyethylene terephthalate, which can be produced by adapting conventional petrochemical routes. Bio-based terephthalic acid can be made from paraxylene via the benzene, toluene and xylene process from renewable feedstocks. Also of note is bio-based mono ethylene glycol, which can be produced via conventional ethylene-oxide routes using bio-ethylene.
The next 10 years could see bio-based polymers having a major impact on downstream polymer production (or not). Only time will tell. HP