Food for oil?

Almost all oil products can, in theory, be obtained from field crops. Faced with global warming and the need to reduce use of and dependence on fossil hydrocarbons, can farmers also become producers of industrial raw materials? The Euro-American consortium ‘Epobio’ is analysing the potential and limitations of this ‘conversion’.

Rape in Lorraine. Rape in Lorraine.
© Michel Adiran/INRA
Emulsion of lipid droplets enclosed in a fully biodegradable proteic surfactant sheath (obtained from rapeseed oilcake). Emulsion of lipid droplets enclosed in a fully biodegradable proteic surfactant sheath (obtained from rapeseed oilcake).
© Alain Riaublanc/INRA
Section of a pine needle showing the plant cell wall. Section of a pine needle showing the plant cell wall.
Melon and marigold seeds, plants used in the production of vegetable oils. Melon and marigold seeds, plants used in the production of vegetable oils. Melon and marigold seeds, plants used in the production of vegetable oils.

Since 1993, the reform of the Common Agricultural Policy (CAP) has encouraged the development of ‘non-food crops’. Although the term is recent, the practice dates from ancient times. Farmers have, for example, always cultivated crops producing fibres (flax, hemp, etc.) for use in textiles or industry. In the 1930s, equipment for Ford cars was made from soy plastic. Who remembers that? The ‘oil years’, to which we will soon have to refer in the past tense, have flourished since then. 97 % of chemical products are currently derived from petroleum, compared with 4% in 1950. An enormous amount of research and development work is therefore required to enable green chemistry, using agricultural products, to rival its black competitor.

But which direction should this work take? Which products are already available? What technological problems will engineers and scientists come up against? And under what conditions will these innovations become competitive? These are the questions Epobio, a consortium of 12 European and American laboratories, intends to answer.

An EU/USA Task Force

The idea for this project, funded by the Sixth Framework Programme, came from the EU/USA Biotechnology Task Force (1).On both sides of the Atlantic, a common desire emerged to assist, by means of multi-disciplinary research, the production of non-food crops for the benefit of consumers and the environment. As explained by Dianna Bowles, a professor at the Centre for Novel Agricultural Products at the University of York (UK) and the Epobio coordinator, ‘this research must be given priority. Our dependence on fossil hydrocarbon resources and climate change represent a threat to our society. However, plants are able to provide us with substitutes for a great number of oil products.’

The main objectives of this research are, therefore, to find products of interest to the industrial sector. However, they still pose a scientific challenge and need to be evaluated with regard to economic viability and risk. Three areas meeting these requirements have been chosen to form part of a long-term plan for 2020: biopolymers, especially those used to produce plastics; vegetable oils; and products derived from the plant cell wall.

Natural Polymers

Plastics, in all their diversity, are united in the fact that they are polymers, i.e. long molecules formed by the repetition of the same chemical motif. Can the many plant polymers be used with the same effect? Currently, starch is the only viable and profitable example, although starch plastics still suffer from a high sensitivity to humidity. The use of other plant polymers has been little explored, and the plastics obtained are often of a lower quality than those produced in the petrochemical industry. However, the genuine ecological interest of bioplastics is worthy of careful examination. On first analysis, they seem to be particularly environmentally friendly as they are fully biodegradable. But is their ecological balance sheet still satisfactory if the full production chain is taken into account, including fertilisers (which release other greenhouse gases), pesticides and transport? Would it not be better to recycle existing plastics? Would it not be preferable, in future, to reserve oil for the production of plastics, since this activity absorbs less than one-twentieth of global production and supplies products that provide full satisfaction?

The answer will depend upon the results of research aimed at improving the efficiency of the biopolymer procedure. Planned approaches include the manipulation of the plant meta - bolism to increase polymer content, the improvement of extraction procedures or even the study of new sources of biopolymers, such as inulin (found in chicory), or proteic polymers.

The Potential of Vegetable Oils

Although research into industrial applications of biopolymers is still in its infancy, the development of vegetable oils has already been credited with some success. As noted by the Swede, Anders Carlsson, a researcher involved in Epobio, ‘Vegetable oils have a similar chemical structure to petrol hydrocarbons.’ Between 15% and 20% of vegetable oil production is already intended for non-food applications. It is, therefore, only a matter of adapting existing industrial procedures to new raw materials.

Biodiesel, produced from rapeseed oil at a price of 78 US dollars per barrel, making it almost competitive in relation to oil, is an example. Soya-based inks, used in printing over one-third of American daily newspapers, is another. There is also castor oil, one of the best industrial lubricants. Diversification in areas where oleaginous crops can be used is, therefore, already being investigated. To increase this and obtain, for example, solvents, paints or surface coatings, work has to be done on controlling the synthesis routes of fatty acids in plants, each one being specially adapted to a type of application.

Is it possible, by transgenesis, to modify the quality or quantity of fatty acids produced by an oleaginous plant? The experts at Epobio emphasise the importance of launching a ground-breaking project, capable of demonstrating the feasibility of this transgenic approach. After all, traditional agronomy also has challenges to answer. European agriculture is characterised by the ‘singularity’ of its olea - ginous crops. The crops with the highest tonnage produced globally each year are soya, palm and coco oils. These three crops are more or less unheard of in the fields of the European Union, where the three leading crops are rape, sunflower and olive. It is, therefore, important to find new non-food applications for the oleaginous crops cultivated in Europe, to increase agronomic research into promising plants, which are currently neglected (flax, castor-oil plants, etc.), and even to plan the cultivation of new oil-producing species, such as euphorbia or marigold.

The Biomass Gamble

The expected upturn in vegetable oil applications could also accelerate the development of biopolymers, which is currently still in its infancy. The extraction of oils from oleaginous plants in actual fact leaves behind a good part of the biomass, which is made up of proteic and sugar polymers. It would be profitable to develop this.

This integrated logic, aimed at exploiting substances from plants, is pushed to the extreme in the concept of ‘biorefineries’, which aim to produce dozens of chemical products from residues of the plant cell wall. The stakes are high, because the rigid wall surrounding the plant cells represents 85 % of the biomass produced by agriculture. ‘The function of the plant cell wall is to support and protect the plant, and this is why it is resistant to degradation by microorganisms. Therefore, it is a matter of using either energy-intensive chemical treatments or complex enzymatic degradation in order to break down the three types of polymers which make up the cell wall: cellulose – the most abundant organic molecule on Earth – hemicellulose and lignin,’ stresses Ralf Möller, a German researcher associated with the project. This chemical or enzymatic degradation is aimed at decomposing these polymers into small molecules, which can then be re-assembled as required by chemists: biofuels from cellulose glucose; resins or solvents from hemicellulose xylose; or even emulsifiers and adhesives from lignin phenols.

However, a major effort is needed to understand the structure of the plant cell wall, and in particular to find ways of developing it at an economically competitive cost, before this grand design for green chemistry can be implemented. The first steps towards biorefineries, which may one day succeed the petrochemical plants at oil terminals, are today being taken in laboratories dedicated to fundamental plant biology research.

  1. See RTD Info, Special Research and Co-operation, July 2005.

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Guayule, the Alternative to the Rubber Tree

University of Arizona & USDA-ARS. © University of Arizona & USDA-ARS.

Hevea, the rubber tree, is well known, but who knows what guayule is? This shrub from dry regions could well become a familiar crop in the fields of southern Europe. Well this is the conclusion of a report from experts at Epobio, published in November 2006, which drew attention to the properties of guayule as an elastomer plant. Two findings were the origin of this report. On the one hand, European industry is very dependent on hevea rubber imports from three countries in South-East Asia, where huge single-crop plantations are very sensitive to parasite attacks. On the other hand, latex allergies, which are on the increase, affect between 1% and 6% of Europeans. So finding new sources of rubber would be in the strategic interests of both the European Union and consumers.

The experts at Epobio reviewed various elastomer plants with names as unfamiliar as they are picturesque (Russian dandelion, golden rod, etc.) before concluding that guayule had the most relevant qualities: it can adapt to the climate of the semi-arid regions of southern Europe, there is agronomic experience of its cultivation in the USA and Mexico, and only a low agricultural input is required in order to obtain a satisfactory yield – to the tune of one tonne of rubber per hectare. The experts stress that further work is needed on the genetic improvement of this plant, which has been neglected by plant breeders, and to develop more efficient methods to extract its gum.

The Future of the Abyssinian Cabbage

Crambe abyssinica Crambe abyssinica © Dr. Win Phippen, Western Illinois University

Engineers are of the opinion that wax esters are one of the most promising biolubricants for industrial applications, especially in motor vehicles. However, they pose a major problem: their only known origin is the spermaceti (an organ located in the head of the sperm whale), and a tropical plant called jojoba. Whaling is banned and jojoba oil sells at the astronomical price of € 5 000 per tonne.

In order for wax esters to rival current mineral oils obtained from petroleum, the experts at Epobio are suggesting a bold solution: the genetic modification of Abyssinian cabbage (Crambe abyssinica), an oleaginous plant rarely cultivated in Europe. The selection of the cabbage is based on three criteria, which together give the plant many advantages over its potential rivals (rape and sunflower): first of all its agronomic properties, as Crambe abyssinica does not require much water or fertiliser; then there is the fact that this plant is not used in human food – a characteristic which the experts consider to be imperative in order for the European public to accept the genetic manipulation of this plant species – and, finally, the fact that it is impossible for the introduced genes to transfer to wild plants. This avoids the risk of genetic pollution, which is often used as an argument against GMO cultivation in open fields. Calculations by the project’s economists have shown that the production of wax esters from Abyssinian cabbage would be economically profitable, particularly if the residual biomass, left after extraction of the oil, is used to produce electricity or heat. The ball is now in the court of the molecular biologists, who have to insert into the plant the genes required for the biosynthesis of wax esters... and of industrial property specialists, as the necessary procedures are protected by numerous patents.