1For every litre of olive oil obtained, 95 kilograms of green waste are thrown away (alpechin, pomace, prunings and leaves). For every cup of coffee, kilograms of pulp, grounds, prunings and leaves are wasted. In most agricultural sectors, more than 90% of plant biomass is tossed aside, causing major pollution problems. Researchers are trying to limit this enormous waste by recovering green waste.

Raimbault columns.

2To this end, they use an invention patented by IRD in 1975: the Raimbault column, a vertical glass tube whereby a controlled amount of gas can pass through a natural organic substrate or compound. This laboratory tool was improved to create bioreactors capable of growing filamentous fungi on agro-industrial waste and mass producing spores which will be used to seed more green waste.

Traditional oil press, Morocco.

3In 2006 in the sugar sector, IRD researchers and their partners identified a fungus which secretes an enzyme capable of breaking down lignin and converting sugarcane bagasse into pulp. Another study conducted in Mexico showed that a fungus could be used to convert this bagasse into cattle food. Other fungi can be used to remove tannins or caffeine from coffee pulp, which can then serve as a source in the production of high added value molecules, such as antioxidants or enzymes.

Sugar cane mill, Cape Verde.

••• Agro-industrial waste can be recovered instead of being dumped •••

4In the olive oil industry, after extracting olive oil, the solid and liquid waste can be used to produce vermicompost, or even earthworms, while agro-industrial residues pre-digested by mould can become a source of production for antibiotics or biopesticides. The future looks bright for bioconversion technologies, with almost limitless possibilities.

“The long-standing solid-state fermentation technique is about to become relevant again. While traditional fermentation techniques have been mastered in many parts of the world, they have enjoyed a resurgence around the world over the past 20 years, with a view to understanding their principles and developing new applications.” 
Gustavo Viniegra-Gonzalez, professor of Biotechnology, Universidad Autonoma Metropolitana, Mexico