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Marco Aurélio Pinheiro Lima

Director of the Bioethanol Science and Technology Center (CTBE)


Green plastic. The Brazilian carbon producer

Sugarcane is an efficient carbon producer, whose potential, we, Brazilians, take advantage of like few others. For 500 years, we have used sugar contained in its juice, consisting of carbon atoms, that one day were part of CO2 in the air, to sweeten our coffee. In the past century, we began fermenting this juice and converting it to liquid fuel.

Currently, Brazilian industrial plants can adjust their production to produce more ethanol than sugar (or vice-versa, in a proportion varying from 40% to 60%), depending on the profit outlook in the next harvest. Not satisfied with this versatility, we discovered a use for sugarcane biomass, which was previously disposed of or partially incinerated.

Incineration continued, but now this took place in boilers producing electricity. This energy generated can assure energy sufficiency of companies in the industry, while allowing possible surpluses to be sold to electric power networks. Thermoelectric gas plants, coal-fueled or nuclear power plants no longer make sense in several sugar-cane producing regions.

In recent years, new utilities for sugarcane resulted from technology. Thanks to the commitment of scientists, governments and private initiative (which sees possible higher financial gains), industrial projects based on ethanol from sugarcane bagasse and other products are beginning to appear. Among these projects, we can highlight one which was theme of a conference at the 2009 Ethanol Summit. I’m talking about green plastic.

On that occasion, when I mediated the respective round table, three large companies (Braskem, Dow and PHB Industrial) presented their products and strategies in what is a promising business area.
Before focusing on the initiatives presented, one must explain what a “green” plastic is. Polymers made of renewable raw material are thus called. Contrary to common belief, they need not necessarily be biodegradable. Polyethylene made of sugarcane is chemically and mechanically equal to material made from petroleum.

The difference is that instead of extracting carbon from the earth and transforming it to plastic, companies use biomass (which absorbs CO2 from the air) and convert it to a polymer. PHB Industrial’s product is different from the others. This company produces Poly-b-Hydroxybutyrate (PHB), a plastic generated by a fermentation process (using natural bacteria, not genetically modified, which feed on the sugar contained in sugarcane and accumulate the PHB inside their cells).

Sylvio Ortega Filho, the company’s Executive Director, states that in certain applications, once it comes into contact with compostable environments, it degrades in about 120 days. Green plastic can replace conventional plastic in several situations. For instance, from bio-polyethylene one can manufacture plastic packaging, such as packs for rice and sugar, disposable diapers, etc., not to mention that there is no need for any adaptations of the current machinery used to transform polymers to plastic objects, using plastic made from renewable sources.

This allows companies to forgo making heavy investments in industrial plants. With this introduction, we must now answer the question: why have large companies invested considerable amounts of money in projects developed to produce plastic made from sugarcane, similar to the kind we can currently find in the market?

Those who took part in the round table debate on the 2nd of June argued the point that this was because of the so intensively debated sustainability. According to corporate executives at the Summit, each kilogram of polyethylene made from sugarcane captures 2.5 kg of CO2 from the air.
In the case of PHB, this figure reaches 4.4 kg, and justifies its green plastic being referred to as a huge “carbon dioxide aspirator”.

Such argument seems to make the difference in favor of renewable plastic in the context of a new reality in which, according to Braskem’s President, Bernardo Gradin, sustainability will increasingly be demanded by the end consumer.
“He is who will determine, irrespective of rules or company initiatives, the speed at which products, processes and business change to become sustainable.”

A more detailed assessment of this issue may reveal interesting features. For instance, it is quite common that companies announce changes in processes or products as they are required due to environmental or social considerations. In many of these cases one can see that the actual (and hidden) reason of such transformation is the economic factor. The case at hand of green plastic is perhaps similar to the history of Brazilian ethanol during the Pro-alcohol program.

Thirty-five years ago, what really made our country invest in the manufacture of cars that ran entirely on ethanol, as well as in the production of ethanol fuel made from sugarcane, was not the discourse “let’s save the planet”. The main motivation then was the increase in the international oil price, which made it difficult to market oil domestically.

At the 2009 Ethanol Summit, two of the three speakers commented that Petrobras has encountered difficulties to fully satisfy the national demand for naphtha, a substance derived from petroleum and used as raw material in polymers and other petrochemical products.
Accordingly, there supposedly is a 30% deficit in the supply of this material.

This may significantly have contributed to the development of plastic and other “sustainable” products, just like in the past the high oil price led to the creation of the Brazilian ethanol industry.
Since the debate is about sustainability, one must add another topic to the debate. One of the first words that come to mind when talking about plastic is waste.

How do bio-polymer producers see this issue? Is it that bio-degradability (which again frees carbon dioxide captured by sugarcane into the air, closing a cycle) is more efficient than conventional recycling methods? One must bear in mind that such methods are subject to restrictions, such as, for example, the impossibility of recycling contaminated plastic (by hospital or organic materials, etc.).

I believe a definitive answer to this issue will only be possible (but must be provided) when our scientists finish a series of calculations. We must measure the green-house gas emissions’ effect on the production cycle of plastic, and calculate fossil and renewable energy consumption if we want to obtain conclusive answers. However, I wish to comment on an interesting alternative mentioned by Diego Donoso, of Dow.

He calls attention to the efficiency of energy recycling involving waste. In this process, plastic residue is used as fuel in the generation of electric or thermal energy.
“Plastic waste is a remarkable source of energy. Each 1 kg of plastic is energy wise equivalent to 1 kg of diesel. To bury plastic is like burying diesel oil”, states Donoso.

The Dow executive says that some European Union countries, the USA and Japan have built energy recycling plants, thus preventing additional fossil fuel being brought to the surface. In Brazil, some initiatives in this regard were undertaken in recent years. However, in the debate on this issue one must take into consideration other aspects such as the cost of implementing such installations. I wish to close this article with the same theme with which I opened it.

Brazil has a raw material - sugarcane -, which is the energy source of the tripoid sugar/bioethanol/electricity.
Green plastic entails a strong environmental appeal, and encourages industry to exploit possibilities of generating other high aggregate value products. This potential must be assessed by our research centers and companies in this industry.

In the Bioethanol Science and Technology Center (CTBE), which I manage, we began the development of a program to create an important computer tool to assist in this task. We call it a Virtual Bio-refinery. Through the computer-based process simulation (in cooperation with researchers, companies and research institutions participating in the program), this tool will assess economic, environmental and social sustainability of a technology under development.

The analysis results will be compared with a standard sugarcane industry production chain, and whenever possible, validated by companies and institutions in the industry. By doing so, it will be possible to analyze the degree of success of new technologies before heavily investing in industrial plants. We trust this tool will be one of our contributions in the quest for better use of sugarcane, this remarkable carbon producer.