When it comes to climate change and sustainability, oil and gas companies positioned as the beginning of the energy value chain have a huge opportunity to strike a conversation. They can at best contribute valuable information on what they do best, that is talking about molecular biology and material science. These companies, leading the hierarchy, can therefore realistically talk about how developments in the areas like plastics, composites, and renewables can make way for a greater impact. As the global energy demand for energy continues to increase, most of the chemicals used in these companies are derived unfortunately from fossil fuels. With the increasing concern of undesirable environmental and socioeconomic consequences of petrochemicals and limited fossil resources, using natural biomass as raw resources for chemical, polymers, and material development is a promising solution towards sustainability and environment-friendly options.
Among the global businesses responsible for 55% of the world’s plastic packaging waste are both state-owned and multinational corporations, including oil, gas, and chemical companies. Currently, there are about 8% of total fossil oils used to manufacture polymers. It is predicted that this number could increase to 20% by 2050. Sustainable polymeric materials possess commendable biocompatibility, which could bring additional benefits for expanded applications. Polymers have largely contributed almost to every aspect of our day-to-day life. While polymers have brought enormous benefits and convenience to society, they inadvertently have also created an undesirable consequence on the environment. Sustainable polymers are a viable option to mitigate the effects on the environment. These can be classified into two major categories – natural polymers and synthetic biobased polymers. Natural polymers like cellulose, lignin, starch, protein, or modified biopolymers, have been widely consumed for the preparation of bioplastics and composites. Synthetic biobased polymers can be derived from a variety of molecular biomass such as plant oils, fatty acids, furan, terpenes, and amino acids. It is worth noting that sustainable polymers are often not necessarily biodegradable. On the contrary, most of them are not biodegradable at all. The use of sustainable polymers can greatly avoid dependence on petroleum resources and reduce carbon emissions.
Unlike petroleum feedstocks, which have carbon-carbon or carbon-hydrogen bonds, a variety of natural biomass possess chemical structures that are carbon-oxygen bonds. These unique structures can be used as new platforms to design functional and readily compostable polymers, bearing new and improved properties. The process, however, has certain challenges like thermomechanical performance and high-cost manufacturing. To overcome this, sustainable polymers must follow through diligent economic planning. Significant progress has been made in the area of sustainable chemistry to transform biomass into polymers. Molecular biomass has the potential to be converted into bio-based polymers in a way similar to the highly successful molecular engineering of petrochemicals. Renewable natural resources like plant oils, fatty acids, cellulose, and lignin, can be widely pursued as precursors for manufacturing sustainable polymers. Let us place special emphasis on the three kinds that could become a potential game-changer. These include lignin, bio-based polyolefins, and polycondensates.
Lignin is a component of the lignocellulosic biomass found in abundance in its natural form and has high prospects as a greener, non-food alternative to petroleum sources. Not only it is the second most abundantly found biomass polymer but is also a renewable carbon source that is readily available. With substitution potential, lignin can be crosslinked with different other kinds of polymers to be used in a variety of material forms. There are also tremendous potentials and gains to transform lignin into polymers. It serves as a three-dimensional polymeric networking agent providing structural support to cell walls. Over 300 billion tons of lignin are present in the biosphere and about 20 billion tons annually biosynthesized throughout the world Certain microorganisms as white-rot fungi can easily degrade lignin and facilitate the formation of soil organic matter. This could therefore make lignin a biodegradable natural polymer. Currently, many oil and gas companies do not make use of lignin at all. The material is greatly under-utilised in chemical and material development sectors, since more than 95% of it is simply burnt as fuel. Only some of its applications are widely used in sectors like dye dispersants, emulsifiers, or cement additives. It is, therefore, worth exploring the biomass through chemical processes like lignocellulose fractionation, lignin depolymerisation, or chemical upgrading.
Industrial lignin production via biomass fractionation is traditionally carried out in paper pulping mills, generating over 50 million metric tons per year. During the paper-pulping process, it is dissolved in alkaline media under high temperature and high pressure. Only about 2% of isolated lignin is used for chemicals, the rest is used as fuel in pulp mill recovery boilers. Now that the paper-pulping industry is shifting towards more sustainable methods, integrated lignin recovery systems can be harnessed to produce lignosulfonates, or other co-polymers rather than burning as low-margin fuel. Energy sectors could look towards novel extraction methods like the production of large quantities of (non-sulfonated) lignin using ethanol biorefineries. One best use of lignin as a biopolymer component is by making thermoplastic polymer blends. Blending with off-the-shelf polymers where lignin is used as a “drop-in” material has considerable potential to increase the content of renewable resources in an economically favourable way. The incompatibility of lignin with other synthetic and biobased polymers makes it challenging to produce blends/composites with enhanced properties.
Next, biobased polyolefins (bioplastics) – given the gigantic volume of polyolefins in the market, it is vital to explore various means to prepare biomass-derived polyolefins. First, understanding polyolefins. These are a type of polymer produced from simple olefins (a hydrocarbon containing a carbon-carbon double bond). For example, polyethylene is the polyolefin produced by polymerising the olefin, ethylene. Polyolefins are used in a wide variety of fields due to their outstanding mechanical properties. High chemical stability and good electrical insulation are their most amazing properties. Commercial polyolefins are actually derived from fossil resources. With alternative options, sustainable production of polymers from polyolefin is not only carbon neutral, but also environmentally viable. Catalytic conversion of bioethanol into ethylene is an attractive approach now considered in the energy sector. However, there can be various other alternatives too. Biomass derivatives like methanol and dimethyl ether can be converted into ethylene through approaches, so-called methanol to olefins (MTO) and dimethyl ether to olefins method. The commercialisation of this bio-based polyethylene can be used in the utilisation of packaging, automobile manufacturing, and construction areas. Honestly speaking, for big companies, projects on bio-based polyolefins represent a relatively small share of their interests. But in the near future, they will have the opportunity to convert their production to avoid environmental impact problems like CO2 emissions, non-renewable energy-saving, greenhouse gas reduction, and waste reduction and management. Despite the existence of numerous plastic materials with a high bio-renewability, only a small fraction of these have been found to have a place in commercial applications. The primary challenge includes reducing the high cost of production, minimising agricultural land use and forests, and, of course, reducing the environmental impacts.
Lastly, talking about the long-chain aliphatic polycondensates – this is an emerging class of polymers that could combine the benefits of polyolefins and condensation polymers. There is a growing incentive to develop long-chain aliphatic polyesters and polyamides, which bridge the gap between conventional polyolefins and polycondensates. This class of polymers has great potential in pursuing green bioplastics by coupling with renewable natural resources. The conversion of natural abundant fatty acids into value-added long-chain aliphatic polymers has been actively explored in recent years. Various monomers were developed, which were further converted into greener long-chain aliphatic polyesters, polyamides, and polyurethanes. In most cases, the physical properties of these long-chain polymers cannot compete with commercial polymers; in some scenarios, most chemistry has been reported without characterisation of critical thermal and mechanical properties. Several key aspects need to be considered: new strategies towards high purity and low-cost monomers derived from fatty acids should be explored by energy sectors in the future.
Sustainable polymers derived from renewable biomass have enormous opportunities to replace or complement some of their petrochemical counterparts. Among them, lignin-derived polymeric materials, biobased polyolefins, and long-chain aliphatic polymers are being intensively pursued in both, industry and academia. In order to stimulate a sustainable economy, sustainable polymers should be grown at an outpacing speed to meet the ever-rising economical and environmental challenges.