The technological and economic potential of various routes to produce Plastics from Trees have been discussed in a report by Nexant. Trees are a prolific and renewable source of raw materials for a host of conversion processes, and have been used as raw materials for centuries (pulp and paper, building materials). The next stage in this evolution of trees and tree-based raw materials is being explored in a host of value-added products, including combined heat and power, liquid biofuels, and renewable chemicals, such as renewable plastics and intermediates. Trees absorb carbon dioxide from the atmosphere as they grow and provide a wide range of feedstocks. Technologies to tap the chemical precursors locked within biomass feedstocks (such as from trees) have improved over time. Products and pathways explored in this report include the following:
• Catalytic Fast Pyrolysis of wood to the key aromatic compounds, Benzene, Toluene, and Xylene (BTX), with generation of paraxylene from the BTX and subsequent conversion to purified terephthalic acid (PTA) and polyethylene terephthalate ( PET).
• Gasification of woody biomass to syngas with subsequent synthesis of methanol, plus methanol to propylene and polymerization to polypropylene.
• Enzymatic hydrolysis of wood to ethanol, with subsequent catalytic dehydration to ethylene and production of high density polyethylene (HDPE).
• Cellulosic plastics pioneered by Eastman (Tenite™ Cellulosics), which find commercial application in tool handles, toothbrushes, golf putters, alternatives to urethanes, etc.
These are compared to traditional fossil-fuel-based routes.
Technology Analysis
Catalytic Fast Pyrolysis to PET (Tree-Based PET)
Anellotech's innovative Catalytic Fast Pyrolysis technology and subsequent processing to produce a renewable, wood-based paraxylene ( p-X), from which tree-based purified terephthalic acid (PTA) is synthesized; PTA is a key ingredient (along with monoethylene glycol) used to make PET:
The tree-based process only differs from the conventional petroleum-based process in the first step, using the CFP™ process to generate the BTX from trees, instead of from petroleum-based naphtha at an oil refinery.
Gasification to Polypropylene (Tree-Based Propylene)
Gasification of woody feedstock generates syngas, which is subsequently converted to methanol via the well-known Methanol-to-Propylene (MTP™) process, and polymerization of the propylene to polyolefin, as shown below:
This process has multiple steps but is rather straightforward, with each of the technologies having been proven commercially.
Enzymatic Hydrolysis in SSF to HDPE (Tree-Based HDPE)
The simultaneous saccharification and fermentation (SSF) of wood chips to ethanol using enzymatic hydrolysis to generate sugars from wood chip feedstock is followed by the dehydration of ethanol to ethylene, which is subsequently polymerized to HDPE.
The pathway assessed here begins with technologies that have been long studied to extract sugars from cellulosic feedstock. The subsequent processes to ferment those sugars to ethanol, from which ethylene and HDPE are derived, are in practice commercially around the world.
Cellulosic Plastics
Eastman Chemical Company was established as an independent supplier of chemicals for their photographic processes. They established two major platforms - organic chemicals and acetyls. Leveraging their knowledge of acetyl chemistry, Eastman began making compounded cellulose acetate, literally "Plastics From Trees," in 1929 soon thereafter, this was sold under the Tenite™ cellulosics trade name (uspto.gov ). Tenite™ cellulosics comprise a family of products grouped in three major categories, as shown below. Early applications of Tenite™ included several iconic consumer products, such as the first football helmets, early TVs, radios, and telephones, Duncan yo-yo's, and others. The process to make Tenite™ starts with softwood trees, which are pulped. This pulp is used to make a cellulose ester which is then mixed with plasticizers and other additives to produce plastic pellets, which are converted into plastic products.These include Tenite™ Acetates, Tenite™ Butyrates, Tenite™ Propionates
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