Butanol production from agrofood wastes is possible

Biobutanol can be obtained by sugar fermentation. One of the main objectives of Waste2Fuels is the development of suitable pretreatments for lignocellulosic biomass, in order to release simple sugars from cellulose and hemicellulose, thus obtaining fermentable streams for biobutanol production.

Apple pomace, a waste from juice and cider industries, has been successfully employed for biobutanol production. A relatively simple pretreatment method, employing only

Apple pomace

Apple pomace

water and surfactants, has been proposed by ITACyL. Thanks to this technology, and after an enzymatic hydrolysis step, apple pomace broths were fermented and yielded about 9 g/L butanol.

Enzymatic hydrolysis

Enzymatic hydrolysis

These results have been presented at the international scientific conference WCCE 10 held in Barcelona (Spain) in October 2017, and they have been recently published in Applied Microbiology and Biotechnology.

Similarly, potato peel from a snack factory was degraded by employing autohydrolysis (water at high temperature) and enzymatic hydrolysis, thus obtaining a fermentable hydrolysate which produced 8 g/L butanol.

Potato peel

Potato peel

These data have been expounded by ITACyL at the international scientific conference ICEMM09, which took place in Bologna (Italy) in September 2017.

Coffee silverskin, a byproduct from roasting industries, was also successfully pretreated by autohydrolysis and enzymatic hydrolysis at ITACyL’s facilities, yielding about 6 g/L butanol after fermentation.

Coffee silverskin

coffee silverskin

These findings will be presented soon at the international scientific symposium ESBES 2018, which will be held in Lisbon (Portugal) in September 2018.

It is remarkable that no detoxification step prior to fermentation was needed for any of the three agrofood waste hydrolysates tested.

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Simple physicochemical pretreatments for agrofood wastes

The selected agrofood wastes (potato peel, apple pomace, brewers’ spent grain and coffee silverskin) contain 8-21% cellulose, 7-19% hemicellulose and 19-33% lignin. In order to use these agrofood wastes as feedstocks for butanol biorefineries, simple sugars must be released from cellulose and hemicellulose. In the Waste2Fuels project, ITACyL has focused on physicochemical pretreatments to degrade these vegetal fibres.

 

Physicochemical pretreatment 1                  OLYMPUS DIGITAL CAMERA

                                                           physicochemical pretreatments

By applying simple methods like autohydrolysis and surfactant-mediated treatments at relatively mild conditions, potato peel, apple pomace and coffee silverskin wastes were efficiently degraded and subjected to an enzymatic hydrolysis which produced potentially fermentable broths containing 30-45 g/L sugars. However, brewers’ spent grain was more resistant to mild pretreatments and its degradation needed the presence of strong acids.