Valorisation of Effluents from Anaerobic Digestion as Single Cell - - PowerPoint PPT Presentation

Valorisation of Effluents from Anaerobic Digestion as Single Cell Protein – Focus on Safe Gas Supply

Borja Valverde Pérez

Bioenergy and Microbial Ecology and Technology Laboratory (Metlab) research groups

August Z. Zachariae, Astrid F. Kjeldgaard, Zahra Rasouli, W ei Xing, Alejandro Palom o, Martina D’Este, Davide De Francisci, Mathias L. Pape, Barth F. Sm ets, I rini Angelidaki @borkram

Agenda

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Microbial protein and its impact on nitrogen cycle Co-cultivation of green microalgae and methanotrophic bacteria Bubble-free membrane bioreactor

Microbial protein and Methane Oxidizing Bacteria ( MOB)

Bacteria have high growth rates and crude protein content compared to algae and fungi. Compared to algae, the cultivation of MOB’s is less space demanding. 1st generation process already exists: natural gas and synthetic nitrogen resources Methane can be produced from most organic waste at a relatively low cost.

[ http: / / www.unibio.dk ]

W hat is m icrobial protein?: protein produced by microbes, which can be used as feed ingredient (EU approved!) W hy MOB?:

N 2

Anthropogenic nitrogen cycle

Haber-Bosch N-fixation NH 3 WWTP GHG’s Manure

Anim al products

N 2 GHG’s GHG’s N 2

Atm osphere

Surface and ground water

Synthetic N-Fertilizer

GHG’s

Leaching/ run-off of reactive N

Croplands Consumers Livestock > 1 % of global energy consumption

~ 145 Mt/ y

Consequences include:

• Clim ate change
• Eutrophication and other chem ical pollution of aquatic

ecosystem s

• Acid Land-use change  deforestation and other habitat

losses

• Natural resources depletion

Closing the nitrogen drain

N 2 Haber-Bosch N-fixation Manure

Anim al products

N 2 GHG’s SCP production GHG’s

SCP

Atm osphere

Surface and ground water

GHG’s

Leaching/ run-off of reactive N

Croplands NH 3 N 2 GHG’s Consumers Livestock WWTP

Synthetic N-Fertilizer

NH 3 CH 4 SCP production

SCP

Nutrient Managem ent – Traditional approach

Manure Biogas – energy Nutrients – fertilizer

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Nutrient Managem ent – Nutrient Upcycling and Reuse in Agriculture

Manure Biogas Nutrients Ferm enter Single Cell Protein Plant Grow th Prom oters

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Focus on Safe Gas Supply

Co-cultivation of algae and m ethanotrophs

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Rasouli et al., 2 0 1 8 ( BEJ)

Co-cultivation of algae and m ethanotrophs

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• The consortium effectively removed organic carbon and nutrients
• Imbalance between photosynthesis and methane oxidation
• Level of explosion is achieved!
• Further optimization is needed

Blue: CH4 Red: CO2 Green: O2

Co-cultivation of algae and m ethanotrophs

Contains the essential am ino acids for chicken

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Bubble-free m em brane bioreactor

Cultivation of a mixed culture of methane

• xidizing bacteria

First experiences:

• Suboptimal supply of gasses leads to

biofilm formation

• Leakage of gases and building of

headspace

• Progressive lose of methanotrophs

Bubble-free m em brane bioreactor

Progressive lose of methanotrophs

• Methylococcales (pink)
• Methylophilales (light green)

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Bubble-free m em brane bioreactor

After gas supply optimization  good oxygen to methane ratio

• Biomass grows in suspension
• Microbial protein content increased  potential recovery of

methanotrophic biomass

• Minimization of gas leakage and avoidance of head space

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0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 g‐ amino acid/g ‐ DW

After optimization Before optimization

Take hom e m essage

• Both proposed options can produce biomass suitable as feed

ingredient

• Co-cultivation of green microalgae and methanotrophs
• Challenges
• Photosytensis and methane oxidation need to be balanced
• Complex process control is needed
• Opportunities
• Valorization of the carbon dioxide from biogas
• Bubble-free membrane bioreactor
• Challenges
• Risk of carbon dioxide accumulation from biogas and methane
• xidation
• Opportunities
• Operation below the low explosive limit

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Acknow ledgem ent

@Metlab_ DTU @I riniAngelidaki

W hat happens w ith the real pollutants?

Who are the bad guys? Heavy metals Impurities Pathogens Pharmaceuticals Antibiotic resistance genes

NH3 NH3 NH3 NH3 NH3

How do we get read of them? Membrane filtration Bio-electrochemical systems

NH3 NH3 NH3 NH3 NH3