Cheap Oil Prices, Not Good for Bioethylene

ethyleneI’m worried about the impact that low oil prices will have on the production of bioethylene and bioplastics. Bioethylene is made from sugars. Currently, ethane, a component of natural gas, serves as a bigger source of the gas ethylene (C2H4), while most of the world production is based on the cracking of large petroleum molecules. Crude oil is distilled into things like jet fuel, gasoline, lubricants and a 5 to 12-carbon mixture known as naphta. Then the naphta is “cracked”, essentially broken into smaller molecules. One of the latter is  C2H4is used as the raw material for many plastics such as low density polyethylene and the more recyclable high density polyethylene. Because all petro-products, including C2H4, are created in such large quantities, mass production drives down the price of plastics. Unfortunately, the whole process also makes a large carbon and ecological footprint, not to mention that inexpensive plastic also encourages the overproduction of some trivial products that generate needless waste.

Compared to petrochemical production, sugarcane-based bioethylene production in Brazil produces 40% less greenhouse gas emissions.  Ethanol is first produced from fermenting sugars. After purification of the alcohol, catalysts chemically dehydrate ethanol to ethylene.

The conversion of ethanol to ethylene is a dehydration. the catalyst is not consumed in the reaction, so it is not shown in the equation.

Finally the same technology is used to polymerize ethylene or its derivatives into a wide array of plastics. In essence then, the prefix in “bioethylene” and “bioplastics” is just used to identify the origin of their raw material.

bioethylene
Since sugar is the source of the ethylene, it is dubbed a “bioethylene”, and the polyethylene made by conventional methods is called a “bioplastic”.

It currently costs about $1,200 US to make a metric ton of bio-ethylene, which only competes with the petro-process when crude sells at over $100 per barrel. Even when oil prices were high, the top biological producer in the world, the Brazilian company Braskem, was producing only 1/20th of the amount made by Saudi Arabia’s two largest petro-producers. Now that crude has tumbled to below $50, neither Taiwan nor Alberta, the world’s two largest ethylene producers, is exactly looking over their shoulder. Meanwhile, chemically, it is possible to develop even more efficient, longer-lasting dehydrating catalysts that will work at still lower temperatures.

Critics of bioethylene point out that reliance on such a means can compete for the availability of arable land for food and animal-feed production and for the conversion of forests into agricultural land. It’s a valid criticism when corn is used. But in Brazil, the percentage of sugar crops currently devoted to bioplastics is less than 1%. In addition, land use would not suffer if eating habits in the industrial world improved, and if we replaced some of the sugar production intended for soft drinks and snacks with what’s necessary to generate plastics for medical devices and other important consumer goods.

It’s no secret that oil production has been recently manipulated by OPEC so that decreasing prices put pressure on Russia and especially on fracking in the United States. That not only makes it difficult on the bioethylene economy, but it hampers sustainable energy development such as solar and wind and encourages people to buy even less ecological cars. It’s a another somber reminder of the towering obstacles faced by a revolution towards sustainable development .

Sources:

Ethylene Formation by Catalytic Dehydration of Ethanol with
Industrial Considerations

Production of Bioethylene: Technology Brief 

Cracking of Petroleum

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