Today, oil is the main resource, both in terms of energy and as a raw material for synthetic chemistry. It has become a rare and expensive commodity, despite the development of so-called "unconventional" deposits.
It should be remembered that oil is very old biomass that has undergone the slow geological process of fossilization (several tens of millions of years!). It is therefore legitimate to ask the question: is it possible with the current renewable biomass to substitute all or part of the oil resource? Is it possible in our plants to "accelerate" the fossilization process, or to develop other chemical or biological processes that would make it possible to have substitution products in a time scale compatible with our needs and that is economically viable?
Biomass to get out of oil
Actually 96 % of oil is used to produce energy and only 4% for other uses. This shows us that it is probably "simpler" to replace these 4% than the energy part, at least in terms of biomass availability.
A distinction must be made between energy applications and those of chemistry and materials.
It is already possible, at least on a laboratory scale, to do everything, both for energy compounds and chemicals. It is already possible to produce all energy and chemical products from oil from biomass (not necessarily economically, especially at current oil prices).
Two approaches are possible: molecular substitution, such as Braskem's biosourced ethylene or Global-bioenergy's isobutene (which can then be converted into iso-octane, the main component of petrol fuel); or functional substitution such as Carghill's polylactic instead of polyethylene.
Microorganisms at work to exploit ... cellulose
Biomass is becoming a credible alternative to oil, the limiting point being access to glucose, the starting point for all metabolic pathways. For even if the latter represents in mass nearly 80% of the terrestrial biomass, it is present essentially in the form of polymers, starch (3% of the plant biomass) which is a reserve substance easy to use and to decompose into glucose. But glucose is also the basis of the human diet, as it is the only source of sugar (other than the glucose and monomeric fructose from fruits and the sucrose from sugar beet or sugar cane) that we are able to digest (since our ancestors invented cooking).
The main non-competing reserve for food applications is cellulose (75% of biomass), but this is very difficult to break down into its basic unit, which is glucose. Indeed it constitutes the "skeleton" of plants that the parallel evolution of plants and their predators has selected to be as resistant as possible according to the principles of Darwinian evolution.
Only micro-organisms, bacteria and fungi are capable of degrading it (herbivorous animals degrade it via the microbial flora of their digestive tract, they do not have their own enzymes allowing this degradation).
Beware of power supply trade-offs
If it is already possible to manufacture all energy or chemical products from biomass, the starting molecule will always be glucose. The whole issue of the success of using biomass as a substitute for oil therefore lies in the deconstruction of cellulose. But even when using cellulose there is not enough biomass available to do everything (especially for energy); it is therefore essential to set up regulations to regulate the use of biomass in such a way as to preserve food and the environment as a priority, with only the surplus to be used for other purposes.
Francis Duchironspecialist in industrial microbiology, University of Reims, France.
Article resulting from the intervention of 15 Sept 2016 during the FESTIVAL VIVANT
