polyethylene (bio-PE) from sugarcane via fermentation into ethanol and subsequent dehydration into ethylene.
Source: From Koopmans [73]. © 2013, John Wiley & Sons.
Braskem is the largest producer of bio‐PE, mainly bio-based high-density polyethylene (bio-HDPE), with 52% market share, with an annual production capacity of 200 000 tons per year made from ethanol obtained from sugarcane [71] and this is the first certified bio‐PE in the world. Similarly, Braskem is developing other bio‐based polymers such as bio‐based polyvinyl chloride (bio‐PVP), bio‐based polypropylene (bio‐PP), and their copolymers with similar industrial technologies. Braskem's current bio‐based PE grades are mainly targeted toward food packaging, cosmetics, personal care, automotive parts, and toys. Dow Chemical (Midland, USA) in cooperation with Crystalsev (São Paulo, Brazil) is the second largest producer of bio‐PE, having 12% market share. Solvay (Brussels, Belgium), another producer of bio‐PE, has 10% share in the current market. However, Solvay is a leader in the production of bio‐PVC with similar industrial technologies. China Petrochemical Corporation (Pekin, China) also plans to set up production facilities in China to produce bio‐PE from bioethanol [74]. LyondellBasell (Rotterdam, The Netherlands) and Neste (Espoo, Finland) have recently announced the first parallel production of bio‐PP and bio‐based low‐density polyethylene (bio‐LDPE) at a commercial scale, being marketed under the trade names Circulen and Circulen Plus [75].
Bio‐PE can replace all the packaging applications of current fossil derived PE because of its low price, good lifetime performance, and especially recyclability [75]. The price of bio‐PE is currently about 50% higher as compared with petrochemical PE, but it will take advantage from the scale‐economy. Current upcoming applications by multinationals include yogurt cups produced by Danone (Paris, France), fruit juice bottles by Odwalla (Atlanta, USA), and plastic caps and closures for aseptic paperboard cartons by Tetra Pak (Lund, Sweden) [76].
1.3.6 Bio‐based Polyethylene Terephthalate
PET is a copolymer of monoethylene glycol (MEG) and terephthalic acid, and one of the most studied polymers to be transformed in commercial bio‐based plastics, which can be derived from plant‐based sugars and agricultural residues. This interest gave life to a technological collaboration between several companies, such as Coca‐Cola (Atlanta, USA), Ford (Detroit, USA), Heinz (Sharpsburg, USA), Nike (Eugene, USA), Danone and Procter & Gamble (Cincinnati, USA), Avantium (Geleen, the Netherlands), and Micromidas (San Jose, CA), to develop commercial processes for the production of bio‐PET. The source of petrochemical terephthalic acid is primarily from the oxidation of p‐xylene, obtained from the catalytic reforming of naphtha. More than 98% of the p‐xylene produced globally is converted to terephthalic acid and the global demand for purified terephthalic acid is expected to exceed 60 million tons by 2020, being most of it used for PET production. As a result of this cost‐competitive demand, bio‐based terephthalic acid made at equal purity and cost as the petroleum derived terephthalic acid would have a clear market advantage as well as a lower price volatility due to the non‐dependence on petrochemical p‐xylene [77]. However, bio‐PET is currently produced from plant‐based monoethylene glycol (bio‐MEG) whereas terephthalic acid is still derived from petroleum. Toyota Tsusho (Nagoya, Japan) and China Manmade Fibers Corporation (Taipei, China) jointly founded a company in November 2010 that manufactures bio‐MEG made from plant derived bioethanol [78]. Other companies such as SCG Chemicals (Bangkok, Thailand) also produce bio‐MEG from residues of agricultural activities including molasses, hay, and bagasse [79]. The first partially bio‐PET product was commercialized by The Coca‐Cola Company (Atlanta, USA) under the trade name of PlantBottle™, where a 30 wt% of bio‐MEG was used for the production of bio‐PET (Company). At the moment, some researchers are working on the synthesis of bio‐based terephthalic acid to obtain fully bio‐PET. This process is based on an integrated method to convert forest residues to isobutanol [80], which can be processed into p‐xylene [81], the precursor of terephthalic acid. Although the 100% bio‐based bottle was released in Milan in June 2015, the so‐called PlantBottle™, shown in Figure 1.5, has not reached yet the price parity to equal the price of producing current Coca‐Cola PET bottles [82]. PepsiCo (New York, USA) also announced the use of a PET bottle made entirely with renewable resources coming from waste carbohydrate biomass obtained from the food industry such as orange peels, oat hulls, corn husks, and potato scraps [83].
Similar to bio‐PE, bio‐PET is not biodegradable but it has the same properties as conventional PET made from natural gas or oil feedstocks. Current partially bio‐PET is used to make a number of products including drinking water and soda bottles, making them environmentally friendly and a new packaging alternative. Products made from bio‐PET have the same qualities as regular PET in its distinctive functions, weight, appearance, and it can also be recycled and reused [79]. This material can be recycled, incinerated, or landfilled, but it can also be intended for disposal by composting, where it undergoes soil degradation to CO2 and water [9]. Enzymatic hydrolysis of aromatic/aliphatic polyesters was first demonstrated in the 1990s for PET with several esterases, lipases, and especially cutinases [84, 85]. Nevertheless, PET hydrolysis by enzymes is a relatively slow process, since the biocatalysts are specialized to attack natural polyesters such as cutin and were not designed by nature for degrading manmade synthetic polyesters in the first instance [85].
Figure 1.5 Image of the PlantBottle™ made up to 30% from biomass and 100% recyclable.
Source: Courtesy of the Coca-Cola Company (Atlanta, USA).
1.3.7 Poly(ethylene furanoate)
A potential green substitute for terephthalic acid is 2,5‐furandicarboxylic acid (FDCA), which is a bio‐based building block that can be polymerized with bio‐MEG to form a new 100% bio‐based polyester called poly(ethylene furanoate) (PEF) [85]. PEF can be synthesized by polycondensation, ROP, and solid‐state polymerization. Polycondensation is the most commercially relevant method but it results in long exposure times to high processing temperatures, around 200 °C, which increases the production cost and, even more importantly, leads to thermal degradation and discoloration of the biopolymer. Solid‐state polymerization (SSP) is a milder process, though a bottle‐grade PEF has not been achieved yet [86]. SSP involves heating of the starting partially crystalline polyester at a temperature between its Tg and Tm, which is used mainly for PET manufacturing to get over its relatively low MW [87]. The company Avantium is developing PEF using bio‐MEG and FDCA coming from the dehydration of carbohydrates [77]. In 2016, it was announced a new technology involving a highly efficient separation technology and catalyst that would result in economically feasible production of FDCA starting from 2016. The planned industrial production capacity is estimated to exceed 300 000 tons per year while the company has established collaborations with major endusers from the food and beverage industry [84].
PEF shows excellent thermal properties and lower Tm values than PET because of which it can be processed at lower temperatures. It has the ability to withstand high temperature due to its higher Tg as well as thermal stability up to 320 °C. PEF outperforms the barrier properties of PET. Specifically, PEF's O2 barrier is more than ten times higher than that of PET, the CO2 barrier is four times higher, and the water vapor barrier is two times higher [88]. Other attractive properties of PEF include excellent mechanical strength, reduced carbon footprint, and ability to formulate in films, fibers, and almost replace PET in water bottles [87]. PEF can be recycled in very similar ways to PET [88]. Recently, the enzymatic synthesis of FDCA‐based polyesters was studied by the groups of Loos and Boeriu with Candida
