Department of Food and Nutritional Sciences

Transcription

1 Department of Food and Nutritional Sciences THERMAL PRE-TREATMENT OF LIGNOCELLULOSIC BIOMASS AS A SUBSTRATE FOR ANAEROBIC DIGESTION F. Kaldis, D. Cysneiros, A. Chatzifragkou, K.A. Karatzas Copyright University of Reading 1

2 ANAEROBIC DIGESTION Anaerobic bacteria (inoculum) Renewable fuels Intricate structure Lignin content (Digestate) 2

3 PRETREATMENT CHOICE 1. Physical (maceration of the substrate) 2. Chemical (alkali or acid pretreatment) 3. Biological (the use of fungi) 4. Hydrothermal (steam explosion) Biomass structure opens up due to thermal expansion, (reduction of the particle size and an increase in the pore volume) The polysaccharides are hydrolysed to simpler sugars Higher degradation rates from the microorganisms of AD 3

4 AIMS Effect of different retention times in a thermal pre-treatment and the correlation between this and the organic load rate of mesophilic anaerobic bioreactors Introducing the liquid part of the thermal pretreatment in AD systems and assessing its effects Modeling the biomethane production data of the experiment using an one phase exponential model 4

5 Batch mode (mesophilic conditions) MATERIALS AND METHODS Inoculum :The effluent of a full scale biogas plant (digesting crops ) Substrate: Wheat straw (WS) Pretreatment: high temperature (140 C) and pressure (2.75 bars)) Retention times (0, 30, 60 and utes) OLR (2, 4, 8 and 12 Kg VS/m 3 ) 5

6 Concentration (g/100g) Concentration (g/100g) Concentration (g/100g) 100,00 80,00 60,00 40,00 20,00 0,00 Total solids EFFECT OF THE PRE-TREATMENT ON THE WS Sugars Glucose Xylose Arabinose The pores of the substrate were opened and the water absorption from the WS increased Part of the sugars were released from the lignocellulosic structure and passed into the liquid phase (no washing step was carried out) The increase trend in lignin concentration can be attributed to the formation of cross-linked aromatic compounds due to the pretreatment 40,00 30,00 20,00 10,00 0,00 Lignin 6

7 Ymax (m 3 /kgvs) CH 4 PRODUCTION (L/KG VS) 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 OLR 2 OLR 4 OLR 8 OLR 12 Y = Ymax (1 e k t t lag ) OLR of 2 kg/ m 3, a retention time of was more efficient OLR of 12 kg/ m 3, a pre-treatment of 60 or led to increased biomethane production 7

8 CH 4 production (L/KgVS) CH 4 production (L/KgVS) CH 4 production (L/KgVS) CH 4 production (L/KgVS) EFFECT OF THE LIQUID ADDITION OLR2 OLR solids treated solids whole slurry solids treated solids whole slurry 0 OLR8 0 OLR solids treated solids 200 solids treated solids 100 whole slurry 100 whole sulrry 0 AD systems with lower organic loads seemed to be more affected by the addition of the liquid fraction of the pre-treatment It is believed that the amount of active microorganisms is playing vital role for the digestion of the thermal treated samples 0 8

9 CONCLUSIONS Thermal pre-treatment was successfully applied on WS prior to anaerobic digestion. This specific pre-treatment seems to have different effect on the process under different OLR. 1. OLR of 2 kg/ m 3 favoured treatment 2. OLR of 12 kg/ m 3 favoured 60 or treatment Anaerobic bioreactors are more likely to handle higher OLR when fed with thermally pre-treated lignocellulosic biomass. In that way, higher volumetric methane yields can be achieved, maintaining the biogas output of existing Plants. 9

10 GREAT THANKS Supervisors team: Dr. Kimon-Andreas Karatzas*, Dr. Aphrodite Chatzifragkou, Dr. Denise Cysneiros Dr. Karatzas group: Marcia, Carolina, Ruth, Oluwabunmi and Ranju Contact: 10