For a Solar Biotechnology Based on Microalgae

Summary

The initial target was to establish the maximum biomass production per unit of time and surface in combining photosynthetic bacteria and microalgae in double layer systems of cultivation. Having shown this technological possibility we have concentrated our effort on setting up a fully automatic system of microalgae monoculture with record and control of all parameters

• 1) Yearly average obtained for a complete year is 20.9 g/m2/day corresponding to a photoconversion yield of 4 %.

• 2) In mediterranean sunlight conditions the theoretical maximum based on a 6.6. % photoconversion yield would be 34.5 g/m2/day as a yearly average.

• 3) Energetic evaluation of the production leads to a value < 1, showing no beneficial fixation of energy.

• 4) Economic evaluation of production cost indicates a cost of — 5 FF/kg of biomass.

Keeping in mind these 4 conclusions our recent targets have been :

• 1) To developp all technologies able to improve drastically the fixation of energy.

• 2) To select strains able to give a final product 10 FF/kg

To reach the 1st target, we have started

• 1) a 3 steps experimental programme (June 81 June 84) on 1 m2, 10 m2 and 100 m2 pilot plant tubular cultivator.

• 2) a new technological way based on “cells immobilized on a support” for production of an exocellular biomass.

In the frame work of the 2nd target we have selected 2 types of strains :

• 1) Red microalgae producing high value polysaccharides (exocellular biomass) and cellular biomass for methanisation (cooperation with ESE/021 B)

• 2) Botryococcus braunii (cooperation with ESE/003/F) producing exocellular hydrocarbons and cellular biomass for methanisation.This project will go on from the 1st June of 81 in the new “Solar Biotechnological Unit” set up by C.E.A. in Cadarache (Biological Department Radio Agronomie Service) Saint-Paul-lez-Durance — 13115 — France.