Continuous wet oxidation pretreatment of lignocellulosic biomasss with subsequent continuous ethanol production
In this project the prospect of implementing a UASB reactor (Up-flow Anaerobic Sludge Blanket reactor) for detoxifing recirculated process water has been examined.
The purpose af the project is to construct a small-scale ethanol production plant for continuously production of ethanol and biogas from different lignocellulosic biomasses. The wet-oxidized cellulose (D-glucose) and hemicellulose (D-xylose) will be fermented into ethanol by mesophilic Saccharomyces cerevisiae and extreme thermophilic Thermoanaerobacter mathranii, respectively. The ethanol is stripped off in situ. The carboxylic acids produced during the pretreatment and fermentation, and remaining carbohydrates and cell biomass is converted into methane in a wastewater treatment system (UASB) reactor). The process will be a closed cycle where the degree of process water recycling is examined in relation to the accumulation of fermentation inhibitors. It will be examined to which extent the lignin degradation products can be removed from the process by wastewater treatment for reduction of fermentation inhibitors. Professor Jack Saddler, University of British Columbia (Canada) will techno-economically evaluate data from these experiments
At the present technology level the price of commercial produced bioethanol is not yet capable to compete with the price of fossil derived fuels like gasoline. A possible solution to decrease the bioethanol production cost is the reuse of process water. Earlier attempts to recycle process water have shown that the build-up of inhibitors decreases the productivity and hereby limits the possibility of reusing the water. In this project the prospect of implementing a UASB reactor (Up-flow Anaerobic Sludge Blanket reactor) for detoxifing recirculated process water has been examined. Bioethanol effluent (BEE), used to simulate an effluent from a commercial bioethanol plant, was produced from wet oxidized wheat straw (60g-straw/l-water) fermented with Saccharomyces cerevisiae and Thermoanaerobacter mathranii A3M4. To determine methane potentials and removal of ihibitors. BEE was evaluated in batch experiments and in a lab-scale UASB reactor. In batch experiments the conversion of acetovanillone, 2-furoic acid and 4-hydroxy acetophenone were examined using the compounds as sole substrages and as co-substrate with BEE. The experiments showed that the conversion of the three compounds together with BEE had a positive effect on both degradation and inhibition levels. Experiments of degrading BEE in a UASB laboratory rector showed that it was possible to obtain a COD-reduction of 80% (w/w) at loadings up to 29g-COD/l/d. Futhermore SPE-GC analysis of the UASB reactor influent and effluent showed that vanillic acid, homovanillic acid, acetovanillione, syringone, acetosyringone, syringol, 4-hydroxy bezoic acid, 4-hydroxy banzaldehyde, 2-furoic acid and phenol were removed from the BEE. Economic calculations based on the obtained experimental results indicate that implementation of a UASB purification step for detoxification of the bioethanol process water can be carried out with an economical gain. It is concluded that implementation of an UASB purification step is a suited method to detoxify process water for bioethanol production hereby reducing the total production costs in a commercial production scheme based on lignocellulose. The need of further investigation of multiple process water recirculations to evaluate build-up of inhibitory compounds is pointed out
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| University of British Columbia (CA) | ||
| Danmarks Tekniske Universitet (DTU) |
Contact
Bygning 115
DK-2800 Lyngby, Denmark
Ahring, Birgitte K. (lektor), 45251600, imt@dtu.dk
Øvr. Partnere: University of British Columbia (UCBC). Department of Wood Science); Forskningscenter Risø. Afdelingen for Plantekemi og Plantegeokemi
