The Carboxylate Platform

Transcription

1 The Carboxylate Platform Nigel Horan

2 Lecture Outline The industry why it should innovate What is the carboxylate platform? Potential benefits Retrofitting and new build Conclusions

3 AD Industry Now over 185 digesters (more than water industry?) Processing 0.72 million tonnes food waste But producing 1.44 million tonnes digestate And >90% recycled to land Feedstock getting more difficult to source Security of land route?

4 Gate Fee

5 Transport and application cost to land We are close to a situation where the cost of digestate recycling may be greater than the gate fee!

6 A Profitable Future? To maintain income the industry needs to keep being innovative The basic flow train offers huge opportunities due to the versatility of anaerobic organisms Parallel advances in thermal technologies (HTC) extend innovative opportunities

7 What are carboxylates? an ester or salt of a carboxylic acid

8 Why the interest in carboxylates Metal salts are high-value oil-soluble, water-insoluble detergents (fracking) Carboxylate platform provides a cheaper route for syngas (carbon monoxide, hydrogen, carbon dioxide) production from a range of waste feedstocks And many high value chemicals..

9 Most important products Butanol ( 2,400/tonne) Succinate ( 2,600/tonne) Acetone ( 1,800/tonne) Ethanol ( 540/tonne)

10 A Route to Acrylamides poly(hydroxypropionate) HO OH O O H O OH 1,3-propanediol O EEP O n HO OH O 3-hydroxypropionic acid HO OH CH 2 NH 2 O O O CH 2 OH acrylamide malonic acid acrylic acid O

11 Conventional MAD Hydrolysis Biodegradable Organic Material (Carbohydrates, Fats, Proteins) Simple Soluble Organics Acidogenesis Acetic Acid Propionic Acid Butyric Acid Long Chain VFA Acetogenesis Acetic Acid H 2 + CO 2 Methanogenesis Acetoclastic Methanogens Hydrogenotrophic Methanogens CH 4 + CO 2

12 Balance of microbial processes for stable conditions Biomass polymers Carbohydrates Proteins Lipids Sugars Amino acids Long chain fatty acids Intermediate Products Hydrogen / Carbon dioxide Acetate Biogas Methane / Carbon dioxide Hydrolysis Acidogenesis Acetogenesis Methanogenesis Net acid producer Net acid remover Ideal ph = 5.0 Ideal ph = 7.4 Conventional MAD at ph 7.4 is sub-optimal for acid production

13 How do we Drive Carboxylate Pure culture with sterile, glucose-based media (ABE) Mixed culture on waste with: inhibition (iodoform at 5g/m 3 ) Organic loading rate control of ph Production

14 ABE Fermentation

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16 Organic Loading Rate (OLR) OLR = Feed rate (m 3 /d) x Feed VS (kg/m 3 ) Reactor volume (m 3) Dictates flow of energy through the system Low OLR encourages Methanogenesis High OLR encourages Solventogenesis Very high OLR encourage Hydrogenesis

17 H 2 Acetone, Butanol, Ethanol CH 4 Hydrogenesis Solventogenesis Methanogenesis HRT (d) >10 ph OLR

18 Products of anaerobic metabolism of pyruvate (Solventogenesis) Succinate Malate Lactate Acetyl CoA Acetate Oxaloacetate Pyruvate Ethanol Acetaldehyde Acetoacetyl CoA Acetolactate Butanol Acetoin Formate CO 2 Butyrate Butylene glycol H 2

19 Hydrogenesis Glucose C 6 H 12 O 6 2 Lactate 2 Pyruvate CH 3 CH(OH)COOH CH 3 COCOOH Low ph route 2 Acetyl-Co 2 Formate HCOOH Ethanol CH 3 CHOH Acetat e CH 3 COOH 2CO 2 + 2H 2

20 Ten routes of synthesis from pyruvate (a) (i) Selected based on OLR

21 Batch Production of VFAs

22 Continuous Culture VFA concentrations of up to 25 kg/m 3 in continuous mixed waste fermentation and rising Waste C:N influences yield (higher C:N better) Low alkalinity encourages low ph

23 Existing Plant Feedstock (type) Pre-processing (screening, blending, pasteurisation) Digesters (long HRT) Biogas & CHP Whole digestate Whole Fibre Dewatering Liquor

24 Easy Retrofit to a VFA Factory To Refinery VFA rich liquor (80,000 mg/l) Feedstock (type) Short HRT Fermenter (to produce VFAs) Thickening/ Dewatering Pre-processing (screening, blending, pasteurisation) Digesters (long HRT) Thickened sludge Biogas & CHP Whole digestate Whole Fibre Dewatering Liquor

25 Circular Process with HTC Feedstock (type) Pre-processing (screening, blending, pasteurisation) Liquor Fuel for energy recovery or to land Solid Product Short HRT Fermenters HTC To Refinery Thickening/Dewatering Liquor Thickened sludge VFA rich liquor (80,000 mg/l)

26 Extraction? POD to POR approach? Strong UK chemical industry Refineries also need to diversify Opportunity to move away from a petrochemical economy

27 Conclusions Thinking about the future will help secure the waste industry future A lot can be achieved in the laboratory environment, but is this real? Economic costing should drive research What does the industry want? How can we involve the refineries