Olive stones (pits) could be the newest ethanol feedstock used
in Spain and could give the olive processing industry an
opportunity to turn the 4 million tons of olive stones it
generates every year into a valuable asset. Researchers from the
Universities of Jaén and Granada have now shown how this can be
achieved in a study published in the latest edition of the
Society of Chemical Industry’s (SCI) Journal of Chemical
Technology & Biotechnology. The olive stone, removed when
processing raw olives for use as olive oil and table olives,
makes up around a quarter of the total fruit. It is rich in
polysaccharides (cellulose and hemicellulose) that can be broken
down into sugar and then fermented to produce ethanol. The team
pre-treated olive stones using high-pressure hot water then
added enzymes that degrade plant matter and generate sugars. The
hydrolysate obtained from this process was then fermented with
yeasts to produce ethanol. Yields of 5.7 killograms (kg) of
ethanol per 100kg of olive stones have been r