Bioplastics and High Value-added Bioproducts Derived from Lignocellulosic Biomass

TAGS:  Sustainability and Bioplastics    

Lignocellulosic biomass has enormous potential for obtaining high value-added bioproducts, especially bioplastics. Lignocellulosic materials are abundant and generally inexpensive, and the current challenge is to produce valuable chemical products with:

• High selectivity, and
• Performance at a low cost

For this reason, the number of pilot projects, demonstrations & industrial biorefinery plants are currently on the rise and paving the way towards a bioeconomy world in which lignocellulosic biomass will contribute actively.

Let's understand the key challenges and opportunities associated with lignocellulose biomass to produce high value-added bioproducts and bioplastics supporting the global bioeconomy.

Lignocellulose Biomass – A Sustainable Bioenergy Source for Future

As we all know, the demand for petroleum-dependent chemical products and materials has increased greatly in recent decades, despite dwindling fossil fuel resources. For this reason, society must now urgently implement alternative energies and high-value resources. Lignocellulosic biomass, therefore, has enormous potential as an alternative feedstock to fossil resources because it is the most abundant and is also renewable. It has been demonstrated that biomass recovery makes it possible to obtain hundreds of high value-added bioproducts, including bioplastics, which are of great interest.

Modern polymerization technologies allow to the production of versatile polymers with highly tailor-made properties and a wide range of applications. Depending on the requirements, polymers produced can therefore be:

• Rigid or flexible
• Transparent or opaque
• Conductive or insulating
• Permeable or with barrier properties
• Durable or degradable, etc.

No other class of materials has such diverse properties and versatile applications. This means that modern life would be impossible without polymers since they provide all humanity with a high quality of life.

Concerns Regarding Depletion of Fossil Resources

The industrial production of a wide range of chemical products and synthetic polymers still relies heavily on fossil resources. The depletion of these resources, together with environmental effects, such as global warming, and pollution are threatening the future of the plastics industry.

In the early 20th century, Henry Ford suggested that the implementation of a bioeconomy would be a logical and necessary step in the growth of any civilization. This implementation was postponed because of how cheap petroleum was compared to any other basic product. However, the competitive price advantage of fossil fuels in the last century has disappeared¹, and concerns regarding fossil fuels have now started to prevail in society, with growing demand for sustainable and environmentally friendly products. For example, the European Union has approved laws to help reduce the use of environmentally abusive materials and has earmarked more funds for the search for materials based on renewable natural resources.

Alternative solutions are therefore being sought to develop sustainable polymers from renewable natural resources to reduce our current dependence on fossil resources and adjust the production rate of CO2 to its rate of consumption.2

Solutions to Replace Petroleum-based Polymers

Biomass and biomass-derived materials are currently among the most promising alternatives. These materials are generated from:

• Atmospheric CO₂,
• Water, and 
• Sunlight available through biological photosynthesis.

Biomass is thus considered the only sustainable source of organic carbon on earth and the perfect equivalent to petroleum for producing fuels and chemicals with net-zero carbon emissions. In this context, lignocellulosic biomass is of critical importance. It has been proposed as an abundant, renewable carbon-neutral feedstock that can reduce CO₂ emissions and air pollution.

Additionally, cellulose, the main component of lignocellulosic biomass, is considered the strongest potential candidate to replace petroleum-based polymers due to its renewability, biocompatibility, and biodegradability.

Opportunities & Challenges Associated With Lignocellulosic Biomass

Lignocellulosic Raw Materials Advantages Over Biomass Sources

The sustainability of producing fuels and chemical products from biomass has been the subject of heated debate. For example, concerns have been raised regarding the sustainability of the current production of bioethanol. This product is based on starch and sugar cultivation, which means that a limited supply of these crops may cause bioethanol production to come into competition with food production.

Lignocellulosic raw materials have advantages over other biomass sources because they are based on the inedible part of the plant and therefore do not interfere with the food supply. Furthermore, lignocellulosic forest, agricultural and agro-industrial waste accumulates in large quantities every year. In fact, the accumulation of this waste on the ground and in landfills causes serious environmental problems that could be solved if this waste were used to make high value-added products. From an economic point of view, lignocellulosic biomass can be produced rapidly and at a lower cost than other agriculturally important bio-products raw materials such as corn starch, soybean, and sugar cane, and it is also significantly cheaper than crude oil.³

Efficient Methods for Lignocellulosic Materials Break Down

However, developing methods for converting lignocellulosic biomass into chemicals and polymers still remains a challenge. Lignocellulose has evolved to resist being broken down, and this inherent property of lignocellulosic materials makes them resistant to enzymatic and chemical degradation. Therefore, in order to modify the physical and chemical properties of the lignocellulosic matrix, lignocellulosic biomass must first be treated, which is usually a costly procedure.

Although lignocellulosic materials are abundant and generally inexpensive, the crucial challenge in lignocellulosic biomass conversion is to produce high value-added chemicals with high selectivity and performance at a lower cost. A relevant number of research projects are currently being carried out worldwide to tackle this problem. Biorefineries have therefore been developed to refine biomass, just as petrochemical plants were created for petroleum production. In this case, however, the goal is to obtain renewable oils and monomers. The number of pilot projects and demonstration-industrial plants related to biorefinery operations is increasing every day.



As mentioned above, one of the most important objectives is to break lignocellulose down into its three main components:

• Cellulose
• Hemicellulose, and
• Lignin

Lignocellulose Biomass Pretreatment Methods

Different pretreatments have been developed to increase the accessibility and biodegradability of these components through enzymatic and chemical processes. Pre-treatment involves applying mechanical, chemical, physico-chemical and biological methods alone or in different combinations. In addition, some pre-treatments include grinding, irradiation, microwaving, steam explosion, ammonia fibre explosion (AFEX), supercritical CO₂ and supercritical CO₂ explosion, SO₂, alkaline hydrolysis, organosolv processes, wet oxidation, ozonolysis, dilute and concentrated acid hydrolysis, and biological methods. It has been observed that the use of different biomass pre-treatment methods in conjunction with other processes, such as enzymatic saccharification, inhibitor removal, fermentation of hydrolysates and product recovery, greatly reduces the total cost of using lignocellulose.

Lignocellulose Biomass Pretreatment Methods
Mechanical	Chemical	Physico-chemical	Biological
Grinding	Alkali Hydrolysis	Steam explosion	Enzymes
Microwaving	Organosolv process	AFEX	Microbes
Irradiation	Dilute & concentrated acid hydrolysis	Supercritical CO2 & CO2 explosion
		Wet oxidation
		SO2
Enzymatic Hydrolysis ↓ Fermentation ↓ Biochemicals, Biofuels and Biomaterials

Once these components are isolated, the target compounds can be obtained through chemo-catalytic and microbial procedures. Future developments in the recovery of lignocellulosic biomass are therefore directly related to improvements in the fields of chemical and microbial synthesis. Thanks to recent advances in these fields, the number and diversity of products based on lignocellulosic biomass have rapidly increased.

Lignocellulosic biomass has more oxygen and less hydrogen and carbon fractions than petroleum-based products. Due to this compositional variety, lignocellulosic biorefineries can obtain more types of products from lignocellulosic biomass than from petroleum. However, more processing technologies are also needed to treat lignocellulosic biomass and many, but not all of these technologies, are still in the developmental stage. For example, bioethanol production and glucose fermentation to obtain lactic acid are well established on the market.

Lignocellulosic Biomass and Platform Chemicals

The first platform chemicals in biorefinery operations may be the sugar compounds obtained from non-food biomass. Efficient release of C5 and C6 sugars with low energy consumption is critical. Glucose is the sugar degradation product of cellulose. The depolymerization of hemicellulose also provides glucose, but it also yields other 5-carbon (xylose, arabinose) and 6-carbon sugars (mannose, galactose and rhamnose).

As mentioned, multiple platforms have been described that use lignocellulosic biomass based on lignocellulosic sugars and lignin. Each one of these building blocks makes it possible to produce many chemical substances and valuable materials through chemical or biological processes, such as:

1,4-diacids (succinic, fumaric, malic)	2,5-furandicarboxylic acid (2,5-FDCA)	5-hydroxymethylfurfural (5-HMF)
Aspartic acid	Glucaric acid	Glutamic acid
Levulinic acid	3-hydroxybutyrolactone (3-HBL)	Glycerol
Sorbitol	Xylitol/arabinitol
Itaconic acid	3-hydroxypropionic acid (3-HPA)

And, from all these substances and their derivatives, bioplastics of high interest can be obtained, including biopolyesters, biopolyamides, biopolyesteramides, biopolyacrylates, biopolyurethanes and biopolyethers.

The world’s largest chemical companies, including DuPont, BASF, SABIC, Dow Chemical, LyondellBasell and Mitsubishi Chemical, are actively participating in the push to recover lignocellulosic biomass. Bioproduction of several platform chemicals, such as ethanol, butanol, lactic acid, levulinic acid, sorbitol, glycerol, 1,3-propanediol, itaconic acid, succinic acid and 2,5-FDCA, has already been achieved. Through research and development, many more products derived from lignocellulosic biomass await commercial production. This, of course, includes a number of building blocks that can be used to produce many novel polymers.

Current fossil-based polymers are therefore expected to be replaced by their bio-based counterparts in the near future. For example, applications for petroleum-derived polyethylene can easily be adapted to use biopolyethylene. With a different future perspective, existing conventional polymers can also be replaced by their newer alternatives. For example, 100% bio-based polyethylene furanoate (PEF) may replace PET in certain applications.

The further commercial success of bioplastics will depend on three factors: financial implications, performance, and environmental impact.


Financial implications, Performance, Environmental impact (L to R)
The first factor appears to be the most significant since it has been demonstrated that biopolymers perform similarly to their petroleum-based counterparts but are more environmentally friendly. The financial considerations can be improved with continued research and development, along with government and private funding. Fortunately, current trends suggest that we are on our way to establishing a global bioeconomy in which lignocellulosic biomass plays a key role. This can and will lead to many more high value-added bio-products and bioplastics, which will increasingly replace petroleum-based bioplastics on the market.

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