Valorization of organic waste streams through fermentation processes



Today, bulk chemicals are typically produced from petroleum resources. As fossil fuel sources are limited, costly and they cause an increase of greenhouse gas emissions, renewable resources are being investigated as an alternative. Various types of biomass resources can be transformed into valuable chemicals. Particularly the use of organic wastes is interesting because they are cheap and abundantly available feedstocks which contain sufficient organic material for easy bioconversion. Through fermentation processes, acids and alcohols can be generated, which can be used as bulk chemicals or energy carriers.

Technological challenge

The fermentation process allows conversion of waste materials containing lipids, proteins and carbohydrates. Organic substrates serve both as electron donors and acceptors. The principal fermentation products are volatile fatty acids such as acetic, propionic and butyric acid, and alcohols such as ethanol and butanol.

The major goal of this Ph.D. is to gain insight in steering fermentation processes towards a major fermentation product at the highest possible yield. The fermenter system will be regulated with different key operational parameters such as pH, hydraulic retention time, organic loading rate, to generate the desired fermentatation product at high concentrations.   

Current practical experience with fermentation for the production of chemicals relies on batch treatment, the use of specific bacterial cultures and single substrates in sterile conditions and separate systems for product recovery. In contrast, this Ph.D. aims to work with continuous fermentation of complex organic materials with mixed cultures. The main problem is that the versatile composition of organic wastes leads to a combination of fermentation products in various amounts.

Therefore the technological challenges are:
1. Development of a continuous bioreactor system for complete waste transformation towards a major fermentation product
2. Integration of separation technology into the fermentation process, i.e. in-situ product recovery to increase the yields

CV researcher: Doga Arslan
graduated: Marmara University, bioengineering (2008)

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