Lecture by Dr. Laigret and biological conversion figures

Article reporting on Dr Laigret's press conference in April 1949 at the Institut Pasteur in Tunis.

The original (scanned) format of this article is not available, it is simply the full transcript. This article contains some interesting conversion figures by the Laigret process (biological action of a Perfringens bacillus)

Doctor Laigret is completing his research on the production of petroleum (by) fermentation of organic matter at the Institut Pasteur

Will the sewage treatment plant or Lake Tunis one day produce oil and gas?

Following a sensational revelation made by "agricultural Tunisia" in 1947, all the local newspapers and certain metropolitan newspapers spread the news that a scientist working at the Pasteur Institute in Tunis, Doctor Laigret, already well known by the work which had led to the yellow fever vaccine (1934) had just obtained oil in the laboratory by fermenting oils and soaps.

At the request of Doctor Laigret, whom too much publicity could only hinder in his research, silence fell on his patient experiences, the considerable interest of which could not escape anyone. The order of silence was lifted only yesterday although a local newspaper believed it could break this order shortly before, which an elementary concern for correction imposed on everyone.

Doctor Laigret brought together in his laboratory the representatives of the press who had already taken an interest in his work and made a declaration to them which specified the conditions and the probable consequences of his studies. Here is the text of that statement:

“The Tunisian press was the first to announce, about a year and a half ago, what had just been demonstrated in a laboratory at the Pasteur Institute in Tunis: that oils are produced by microbial fermentation. The microbe which causes the "petroleum" fermentation was discovered, this fermentation had been reproduced; Hydrocarbons had been created, not by chemical synthesis, but by the very process that nature employs to constitute the deposits from which industry extracts the fuels essential to modern life.

The important fact was therefore the knowledge of the biological phenomenon which generates natural oils. The repercussions that such an acquisition was likely to have in the practical field, it was still impossible, at the time, to foresee them. One could not envision them without a certain vertigo, nor also without certain doubts.

Indeed, the first oils obtained in the laboratory had been obtained by fermentation of olive oil: an expensive, rare product, which had to be reserved for food and for which there was no question of industrially making essences for engines. The other vegetable oils studied subsequently, peanut oil and linseed oil, provided the same results, interesting from a doctrinal point of view but without more precise scope on the industrial level.

The first results worthy of being retained for practice related to a little known oil: jatropha oil. Its fermentation was studied on the advice of a French engineer from West Africa, Mr. François. Jatropha is a type of castor oil plant that grows wild in Sudan. Its oil is toxic, therefore inedible; she has not yet found a definite job in the industry. It has been shown to be very interesting in our carbide fermentation tests: 80% of the weight of this oil can be transformed into carbides.

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Tests were then carried out with residues of olive oil, with this black sludge which is deposited in the tanks, which we call the “Battery funds”, and which are unfit for consumption. The yields were the same as with good quality oil.

The study thus oriented was to continue on a whole series of food waste: butcher's meat waste, the most common miscellaneous detritus, the peels of oranges for example. Orange peels subjected to the action of the petroleum ferment provide almost 38% of their weight of carbides: meat waste 47%.

Manure from which only methane gas has been extracted as carbide until now, has provided liquid carbides. This has an importance for agriculture which does not need to be stressed.

Finally, a finding that goes beyond all the others, we extract significant quantities of oil from sewage sludge. The experiments were made with sludge from the sewers of Tunis. These sludges, despite all that they contain sand, gravel, various non-fermentable impurities, nevertheless provided 15% of their weight of crude oil.

In short, all or almost all the wastes of human life, animal life and plant life are taken up, which pass to the state of carbides under the effect of a fermentation suitably carried out and rationally exploited.

Nothing can be said about the techniques we use. The issue is so important for the economy and national defense that no indiscretion is allowed. We can announce that the adjustments are made, that the laboratory research is finished. We can add that a priori, once the installations have been fitted out, the cost price of fermentation oil will be that of natural oil less drilling costs; but everyone knows that today the expenses which precede the exploitation of a well are considerable.

In other words, we are going to have on the very surface of the ground the oil that until now nature has only produced in depth and that we will fetch with a rotary machine up to three thousand meters. We will have this oil in France and in the French overseas territories. It is therefore, with all certainty, a great economic revolution, and also military, let us not forget, that is coming. I wanted the Tunisian public to be the first to know about it. "

hydrocarbon yields of various products

Doctor Laigret then gave details of the hydrocarbon yields he obtained by fermenting various products in his laboratory.

According to his calculations vegetable oils have substantially equal returns whatever these oils. They give 800 liters of crude oil and fuel gas 200 m3 per tonne processed.

Kitchen meat waste provides 450 liters of crude oil and 146 m3 of gas per tonne. Dried orange and lemon peels give 187 liters of crude oil and 300 m3 of gas per tonne (in this case, the fuel gas yield is equal to that of a higher grade hard coal, the oil being supplied in addition ). Animal manures (especially rabbits) provided 112 liters of crude oil and 265 m3 of gas per tonne.

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Samples taken at the various levels of the settling tanks of the Tunis sewers, it follows that with one tonne of this waste subjected to fermentation, 185 liters of crude oil and 124 m3 of combustible gas are obtained. But it should be noted with regard to this volume of gas that the spontaneous fermentation of the sewers previously eliminated an unknown and certainly significant quantity of methane gas.

The results of tests on dead leaves have not yet been quantified.

The average composition of crude oils obtained by fermentation of various organic materials is always substantially the same and similar to that of natural oils. In round figures, established according to the average of the experiments, this composition is 40% of gasolines known commercially "tourism" and "heavy goods", 45% of heavy oils constituting the "gas oil", the "guel oils »And engine greases, while 5% of crude oil is resolved into cracking gas and 5% of residual water remains very strongly ammoniacal and recoverable for the manufacture of ammonium sulphates useful in agriculture.

One can also note among the fermentation products of coke. In addition, by conducting this fermentation in a certain way, it was possible to obtain from slush a tar and a kind of asphalt and from linseed oil an asphaltic pitch which gave the distillation 56% of its weight of petroleum, which could perhaps become the origin of a practical way of transporting the fermented products in solid form before distillation.

A report last sub product from the fermentation cycle in tests on dead leaves: a resin that can be an excellent polish.

And Doctor Laigret ended his presentation by proceeding to the distillation of a pitch obtained by fermentation, a distillation which gave crude oil in a test-tube and methane in a jar, methane which was ignited and whose flame served as eloquent conclusion.

scientists consequences

From a purely scientific point of view, the work of Dr. Laigret is obviously of great importance. If, apart from purely chemical methods, we have been able to produce petroleum at various times in the laboratory, it is to our knowledge to Dr. Laigret that the essential merit goes: on the one hand, to have obtained this result with a bacterium extremely widespread on the surface of the globe which we already suspected that it participated in the fermentation of petroleum, on the other hand to have demonstrated that this bacterium could by itself cause this formation, whereas it was believed that the action of various bacteria was (passage illegible)… ment reconstituted in his laboratory, if not the unique process - which is not yet known - at least certainly one of the processes of natural formation of petroleum.

The action of anaerobic bacteria, that is to say, acting shielded from air and oxygen on organic matter in prehistoric inland seas, was, in fact, long considered by many to constitute the genesis of oil slicks. The results obtained by Dr Laigret confirm this hypothesis in all points, which obviously does not exclude that other hypotheses may in the future also prove to be correct.

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practical implications

In the practical field, the work of Dr. Laigret will have an even greater importance.

As he himself specified in his statement, we can now consider several main uses of his discovery: the transformation into oil and gas on the one hand of purghère oil, on the other hand of slush, and finally garbage, because it is understood that there can be no question of using edible products or products already used by industry for this purpose.

The purghère - euphorbiaceae parent of the castor bean - or pine nut or American castor bean bears seeds whose oil, toxic, sometimes enters partly in the composition of certain soaps or is used to make varnishes. But this oil is very little used, and vast cultures of purghère, which one does not know moreover if it would acclimatize in Tunisia procured significant quantities of oil.

Regarding slush, the question interests us more directly because it is very possible that the Borgel elevation plant will soon be equipped to produce oil and gas by fermentation. Indeed, the fermentation being initiated in the sewers would continue in the settling tanks. Without the need to build special tanks. All that would have to be done would be the distillation and methane gas recovery facilities before and after fermentation.

Finally, the possibility of treating household waste from a city as large as that of Tunis should not be neglected, a treatment which would be all the easier as fermentation has better effects when various products are treated together.

These are, moreover, only simple indications, for the fields in which this new industry will be able to operate, if it is created, will be innumerable. Do not fish give about 70% of their weight of hydrocarbons and the sludge of Lake Tunis does not contain millions of corpses of these fish? Oil mill pile bottoms, canning waste, so many other elements considered until then as good for waste, can they not suddenly turn into precious oil?

The imagination has the opportunity to give free rein, waiting for experience to tell us what is feasible and profitable and what is not.


Whatever the practical applications of Dr. Laigret's discovery in the future, the Institut Pasteur in Tunis can be proud of the work of this remarkable scientist who honors France and Tunisia. At the moment when he declares that his laboratory research is finished concerning the obtaining of petroleum by fermentation, which moreover is only partly correct, it is only fair to pay him a well-deserved tribute.

It is also right to associate with his name that of those who, for months, have assisted him with enthusiastic dedication, in an overwhelming task: M. Sassi, chemist, MM. Chaignet and Chedli Bougbaha, preparers from the Pasteur Institute, as well as Mr. Jouin, from the mining laboratory, whose help was invaluable during the first production tests for bacterial oil.


- A 1949 S&V article: Biomass and synthetic oil, work Laigret
- Presentation of Laigret project
- Topic on forums: renewable and green oil by Laigret
- Documentation on the oil Laigret

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