Green Chemistry for Polymers

In the long-term industry will have to find substitutes for fossil fuels as supplies diminish and costs rise: so what is a sustainable resource for synthesis of conventional plastics? At Green Polymer Chemistry 2012 in Cologne, Germany, AMI brought together experts from agriculture, chemical engineering, biotechnology, the polymer industry and sustainability managers from brand owners and the automotive sector to hear all the angles on this topic.

LMC International studies the agricultural including sugar, grains and oilseeds. Worldwide, corn wheat and cassava accounted for 1.7bn t in 2010/11, and sugarcane and sugar beet generated 160Mt (the lead producer is Brazil). On the vegetable oil side, palm predominates at 48Mt (85% is grown in Malaysia and Indonesia) and is unique in being harvested from trees each year – the other oils are from seeds. The agricultural industry is already seeing a ‘battle for acres’ globally. This began in 2002 with the drive to use bioethanol/biofuel, which increased demand for arable land for growing feedstock. By 2010 the area under cultivation had expanded worldwide by 70M hectares. Besides biofuels, there are other factors such as the rise in per capita income in Asia, which means that consumers are eating more meat thus increasing the demand for animal feed. More land can be cultivated from areas such as the Black Sea, South America and South East Asia if it is cost-effective. Bio-based plastics and other fine chemicals are now being produced from agricultural feedstocks and the challenge is to find sources that are sustainable in this global marketplace.

Brand owners and retailers have studied sustainable sourcing extensively, with all of the majors operating policies including Walmart, Carrefour and Tesco. Dr Jan Kees Vis at Unilever has been involved in projects such as the Sustainable Palm Oil roundtable; the aim of this brand owner is to double "the size of our company while reducing our environmental impact”. This includes a plan to source 100% of agricultural raw materials sustainably: palm oil is the top material at 1.4Mt/annum primarily for surfactants, then paper, soy and sugar, followed by other oils. Unilever has put together a Sustainable Agriculture Code and wants to use products with certification, such as Rainforest Alliance and Fair Trade. There are many other issues such as the need to ensure the security of food supplies. Thus brand owners will ask questions of suppliers about the sustainability, not just renewable sourcing, of new products.

The automotive industry is also pushing forward in this arena. The Ford Motor Company has some notable new developments in using renewable sources, such as soy polyol-based polyurethane foam, which cut CO2 emissions by 14.3Mt. One problem is the large number of cars produced, currently 4.8M/annum, so any material specified must be available in considerable quantity. In the case of soy, the United Soybean Board was keen to find a use for the oil as the bean was being grown for animal meal and oil was a side-product. There is also use of recycled materials and natural fibre reinforcements like hemp, sisal and wheat straw.

Ford is using a bio-TPU from Merquinsa Mercados Quimicos (now owned by Lubrizol), which has a renewable source for the polyol component. The Brooks running shoe was switched to part bio-TPU in the sole two years ago, it is also used in Smith Optics ski goggles, and is compounded for injection moulding consumer goods. The material offers up to 40% less CO2 emissions than classic polyurethane according to the PAS 2050 greenhouse gas (GHG) emissions standard.

The Brazilian sugar cane industry is the largest in the world. Braskem has utilised this sugar as a source of feedstock to make its ‘green’ polyethylene and polypropylene with current capacities at 200kty and 30kty respectively. 86.5 tons of sugar cane gives 7200 litres of ethanol and 3 tonnes of polyethylene. Brazil has vast areas of arable land that could be used to develop this industry and Braskem is studying all aspects including ways to increase yield. The company uses BonSucro-certified ethanol.

There have been several technology breakthroughs in the past year in producing substrate from cellulose (so-called second generation feedstock). The M&G Group has PROESA Technology and built a pilot plant in 2009. This generates C5 and C6 sugars in a continuous process. The plant has been in operation for 400 days continuously and many enzymes and 15 types of biomass feedstock have been tested. The Crescentino demonstration plant will have capacity for 40kt/a cellulosic ethanol and will generate 15 MW of power from the lignin by-product to the grid, as well as selling the ethanol. The VTT Technical Research Centre of Finland has examined the feedstock potential of the country’s forests, where growth rate of trees is expected to rise by 25% in the next five years due to global warming. VTT has piloted the manufacture of ethanol from lignocellulose with UPM including recycled paper. Biomethane can also be used in the olefin supply chain: methanol to olefins (MTO), ethylene and propylene was investigated by Mobil in the 1980s and Total Petrochemicals built a demonstration unit in Feluy in 2010. VTT has also experimented with wood oils and the manufacture of LDPE from tall oil.

Biomass production amounts to 165bn t/year, 50% cellulose and 24% hemi-cellulose. Sud-Chemie AG sees sugars as the new oil and has partnered with SABIC in the sunliquid process, which takes lignocellulose feedstock and converts it to fermentable second generation sugars or ethanol, which can be used to make monomers for plastics like PE and PET. Around 4 tonnes of straw yields one tonne of ethanol. The sunliquid process works with different renewable feedstocks. The biggest potential source of lignocelluloses is rice straw in Asia at round 750 million tonnes. Sud-Chemie also has a Liquibeet technology using enzymes to liquefy sugar beet.

Petron Scientech was founded in 1991 in Mumbai and Princeton and has ethanol to ethylene technology with a high conversion rate around 100% with close to 99% ethylene selectivity. Reactor design has to factor in the highly endothermic reaction and heat recovery. It has supplied technology to companies such as Oswal in India, which maximises use of sugar cane – sugar is sold, bagasse is sent to fuel power stations and the molasses is used to make industrial ethanol and from there to make polyethylene. Greencol Taiwan (JV of CMFC and Toyota Tshuho) has taken technology to produce monomers for bio-PET and the new plant is due to start up in 2012.

There has been great progress towards production of fully bio-based PET. Avantium has generated a ‘technical drop-in’ for the terephthalic acid component from furan dicarboxylic acid synthesised by dehydration and oxidation from carbohydrates. This FDCA can also feed into polyurethane and polyamides. The partners in this work include Teijin, Coca Cola, Solvay, Rhodia and Danone. The PEF material has been tested on commercial blow moulding, fibre and film lines and has a higher gas barrier than PET. A pilot plant is being constructed at Chemelot in the Netherlands with capacity of 40t/year.

The Wageningen University has studied crops as chemical sources, looking at algae for fatty acids, dandelions for latex, and seaweed for biorefineries among many other projects. They have examined pathways to a wide range of biobased monomers including furans for polyamide and polyester production. Biocatalysis is the preferred technology with relatively mild reaction conditions.

Novozymes has the largest market share of industrial enzymes worldwide and 60 years of experience. The company sees renewable chemicals as a key to meet the demand from the growing world population, which is anticipated to reach 9bn in 2050. This will move the renewable chemicals industry from ”tech push to market pull”. Current chemical engineering has been optimized for decades and the biotech industry needs to catch up and compete on cost and performance. Genzyme has Cellic to produce ethanol from biomass at USD 2-2.5/gallon and more competitive enzymes coming on stream now. The company is a partner in the M&G cellulosic ethanol plant and also involved in projects with Cargill, Braskem and ADM. The work with Cargill involves bio-acrylic acid production for applications from diapers to coatings and adhesives.

Other companies focus on the enzymatic routes to make monomers from renewable sources, like Global Bioenergies. The focus is on direct fermentation to give products such as propylene and butadiene. Synthos is a partner in the latter project. The company develops possible synthetic pathways with corporate clients and uses databases of enzymes to find suitable catalysts for cloning in bacteria. A pathway to isobutene has already been established.

The use of more conventional catalysts has been reviewed by the Leibniz Institute for Catalysis, which has been studying the production of monomers from vegetable oils. The vegetable oil market in Germany amounts to 5.16Mt of rape seed, 50kt of sunflower, and imported sunflower, linseed, soybean (from USA), castor oil (India), palm and coconut oil (Malaysia, Indonesia). These oils can be used in synthesis of polyurethane, polyester, polyamide, polyacrylate and epoxy resin. For example, Emery Oleochemicals has achieved ozonolysis of oleic acid which can be used in polyamide 6.9; Evonik has chemical pathways for ricinoleic acid to give polyamide 10.10 and 6.10; Arkema has polyamide 11 from 11-undecanoic acid from castor oil and BASF has made polyamide 6.10 and polyols from sources such as castor oil. The industry needs to become more competitive and this includes breeding strains of plant with higher levels of useful fatty acids, like high oleic sunflower oil. There is also potential to produce oils from bacteria or algae.

Several major chemical companies have prioritised sustainability including Royal DSM. The company is producing polyamide 410, thermoplastic copolyester and UP resin from bio-sources and comments that OEMs ask, "Is it competing with the food chain?” Another factor is that like all renewable technology the price has to be comparable to existing products as the markets are not prepared to pay extra. The Biosuccinium project with Roquette to produce succinic acid in a yeast-based process is scheduled for large scale production (10kt) in Italy in 2012. There are also plans to make bio-based adipic acid, a precursor for polyamide 66.

Cathay Industrial Biotech based in China is the largest global producer of biobutanol with over 7M gallons produced in 2011 and it is moving into lignocellulose technology. The company has also commercialised a polyamide 5 monomer from lysine via decarboxylation to pentamethylenediamine, which can be combined with a biobased di-acid. One issue was bioprocess impurities, which represented a new challenge. The new monomer could be used in polyamide 5,10, 5,6, 5,4 or 5,X. The company is looking for partners to develop these materials.

There is a lot of interest in technology to synthesise polymers from carbon dioxide. Several companies worldwide are involved in the production of polypropylene carbonate including Bayer MaterialScience (BMS) and BASF in Europe, Novomer in the USA, SK Innovation in Korea, and Mengxi in China. BASF is motivated by low monomer costs, reducing CO2 emissions trading and the abundant feedstock from power plants. It is testing the material in several applications such as an ABS replacement in electrical appliances, in agricultural films and in paper coatings. One issue is the low activity of catalysts and the need to remove the catalyst after polymerisation.

BMS has generated polyether-polycarbonate polyols from CO2 for use in polyurethane, as well as producing the plastic polypropylene carbonate. The CO2 supply is scrubbed at the coal-fired power plant and then reacted with propylene oxide. It has taken the company time to reduce the by-products and improve catalyst use towards its ‘dream production’ target level. Slab stock foam has been produced and tested.

The biobased chemical industry for fine chemicals is moving toward reality. One driver is the changes in cracker operation that will reduce the supply of elastomer C4-C5 monomers. The Materia Nova Institute has reviewed the research into building blocks for polymers, including succinic acid (DSM, Bioamber, Roquette, Mitsubishi Chemical), sorbitol (Cargill, ADM, Roquette), propylene (Braskem, DuPont/Tate & Lyle), butadiene (Goodyear, Lanxess, Michelin, Synthos, Genomatica) and caprolactam (Draths). Solvay has a pilot plant to generate 60,000t of partly biobased PVC in Brazil as another example. Vincent Berthe speculates that the biobutanol platform could become bigger than bioethanol: it can be made directly by glucose fermentation.The question of sustainability revolves around the competition for land and the impact on agriculture. The NNFCC in York has studied crops for non-food use for many years and this is not novel – 40% of sugars and starch in the EU are already grown for other purposes than food. John Williams calculates that around 250-800M hectares of land are available for crops for bioenergy and fine chemicals excluding forest, protected areas and land for increased food production. The EU has renewable energy mandates that put pressure on the biomass supply chain. This makes predicting the future more difficult and 2030 and 2050 calculations are usually given based on several scenarios. The NNFCC overall prediction is that bio-based plastics will reach around 1% of the market by 2020 at 3-5Mt, up to 10% by 2030 at 43Mt and to 20% of the market in 2050 at 155Mt.

The Green Polymer Chemistry conference in Cologne provided a unique opportunity for agriculture, biotechnologists, brand owners, venture capitalists and polymer experts to gather and debate the issues. Green Polymer Chemistry 2013 will be held at the Maritim Hotel, Cologne, Germany from March 19-21, 2013. Paper offers should be sent to Dr Sally Humphreys ([email protected]) before the deadline of September 14, 2012.