3. Conclusion

Because of their ability to degrade organic substrates, bacterial processes could be used for the bioremediation of agro-industrial wastes, such as those from the dairy or sugar industries. While fermentation alone can hardly compete with the methanization process, the coupling between fermentation and photofermentation is a promising approach that could, in theory, enable almost complete conversion of the substrate (waste) into CO ₂ and H ₂ . This concept has given rise to numerous projects such as the European HYVOLUTION program. Much remains to be done to optimize the interface between the two processes and automate the whole, for which pilot plants are planned. Fundamental research into fermentation (particularly at high temperatures) and photofermentation will also need to be carried out in parallel...