Dow is currently building a 770-million-lb/yr train to produce Dowlex linear low-density polyethylene (LLDPE) in the middle of a sugar cane field in Brazil. Once online, the unit will be the first fully integrated sugar-cane-to-polyethylene complex in the world, according to the company. In the process, sugarcane juice is fermented, centrifuged and distilled to produce ethanol, which is then converted into ethylene gas using heated, catalyzed dehydration. The ethylene is then polymerized to make polyethylene.
One ton of sugarcane yields 22.5–23.8 gallons of ethanol, which makes 88.2 lbs of ethylene that can be transformed into 96.5 lbs of polyethylene.
According to Dow, the sugarcane-based route to polyethylene “has a negative CO2 output (it removes more CO2 from the atmosphere than it releases).”
“State-of-the-art catalyst technology yields ethylene with the same purity as that obtained from petroleum,” says the company. Once online, the facility will also be completely energy-self-sufficient, as bagasse from the sugar-cane-crushing process will be used to fire the boilers onsite (and this will produce enough surplus energy to power a nearby city of 500,000 people). Each ton of sugarcane yields 240-289 kg of bagasse.
“Our facility in Brazil provides an economically compelling story, because in Brazil, biological feedstocks and fossil feedstocks are equivalent on an energy basis,” says Maughon. “With a long growing season, highly productive land, and a crop that is tailor-made for chemical production, the unique situation in Brazil allows for the production of commodity polymers from biofeedstocks there.”
“However, this also highlights some of the disadvantages of renewable feedstocks in general — namely, that many crops don’t make sense when compared with conventional fossil feedstocks, and an opportunity in one geography is not necessarily translatable to other geographies,” adds Maughon. “We particularly like those processes that allow us to make the polymers we already market today from a renewable source — we know how to tailor the properties and we know what properties are desirable.”
He adds: “When the renewable feedstock leads to new materials, the challenge quickly turns to developing new markets for materials with completely different properties, and this can become a daunting proposition for initial implementation.”
NatureWorks LLC (Minnetonka, Minn.; www.natureworksllc.com), a joint venture between Cargill (Minneapolis) and Teijin Ltd. (Tokyo, Japan), is said to be the largest producer of bioplastics in the U.S. At its facility in Blair, Neb., the company uses corn sugar to produce plastic packaging materials and fibers made from polylactic acid (PLA), a polymer that is made by fermenting starch from corn and other crops into lactic acid, which is then polymerized.
Other companies are also making PLA from renewable feedstocks. These include BASF (more), U.S. Agricultural Research Service (more), USDA (more), Harbin Weilida Pharmaceuticals LLC (more), Cargill Dow, for which the company won this magazine’s Kirkpatrick Award (more), and others.
Similarly, through its joint venture company called Telles, ADM and Metabolix Inc. (Cambridge, Mass.; www.metabolix.com) have developed a process for producing the biopolymers PHA (polyhydroxyalkanoates), which the companies call Mirel, by fermenting renewable resources such as corn sugar (more). Once the first Mirel facility comes online in late 2009 (adjacent to ADM’s corn wet mill in Clinton, Iowa), it will have nameplate capacity of 50,000-m.t./yr and produce 110 million lb/yr of Mirel in pellet form.
The company has said that production of Mirel bioplastics is not limited to corn as the primary feedstock, but could eventually be adapted “to sugar cane in Brazil, palm oil in southeast Asia, coconut oil in India or even switchgrass in America.”
Metabolix has also been working to bioengineer switchgrass plants themselves, to create modified crops that are able to produce significant amounts of PHA bioplastics within their plant structures — a breakthrough that has the potential to maximize the potential of biomass crops that are destined for bioplastics productions, says the company (more).
Meanwhile, in October 2008, Cargill (Minneapolis, Minn.; www.argill.com) cut the ribbon on a $22-million facility in Chicago, which produces so-called BiOH polyols from soybean oil rather than conventional petroleum-based feedstocks. The polyols are used for producing polyurethane for furniture, automotive and other markets. Cargill introduced the polyols in 2005 using a toll process, and added its own production capabilities in Brazil in 2007 (more).
Dow has also partnered with NREL to develop, demonstrate and commercialize mixed-synthesis catalysts to produce mixed alcohols from biomass, and with Süd-Chemie AG (Munich; www.sud-chemie.com) to develop improved catalysts for the conversion of syngas (including but not limited to biomass-derived syngas) into chemicals including alcohols and olefins, and the conversion of ethanol to derivative chemicals.
Meanwhile, ADM and PolyOne Corp. (Cleveland, Ohio; www.polyone.com) are collaborating to develop bio-based plasticizers, which are used to make plastics softer and more flexible. The global plasticizer market is valued at $11 billion/yr, and is comprised mostly of petroleum-based products. The alliance will pursue greener plasticizers using corn and oilseeds as the primary feedstock.
* This story is an online-exclusive sidebar for Renewable feedstocks: Trading barrels for bushels