Biotechnological Conversion Processes

Biofuels, Microbial fuel cells, microalgae technology (cultivation, oil production), Biofuels from Agricultural Wastes and By-Products

Biofuels, Microbial fuel cells, microalgae technology (cultivation, oil production), Biofuels from Agricultural Wastes and By-Products


Fichier Détails

Cartes-fiches 149
Langue English
Catégorie Technique
Niveau Université
Crée / Actualisé 06.02.2022 / 11.02.2022
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Why are heavy metals in the culture broth undesireable?
 

• Cu, Ag, As, Pb, Hg, Cd are toxic to bacterial and human beings at low concentrations (e.g. chelate formation, binding to enzymes)

What is the source of heavy metals in the culture broth?

 

• Cu, Pb – Desinfection in agriculture, Pipes
• Zn – veterinary medicine

What are technical options to prevent high concentrations of hydrogen sulfide in biogas plants?

1. Injection of air (biological)
2. Addition of ironsalts (precipitation)
3. Activated carbon (adsorption)
4. Gas scrubbing (biological)

Why is H2SO4 undesireable?
 

• Toxic to bacterial and human beeings at low concentrations (100 ppm)
• chemical precipitation of heavy metals (micronutrients)
• odor emmission
• corrosive

Inhibition by Ammonia
Which is the source of Ammonia?
Which could influence the equilibrium?

Mainly manure. Use manure only as a co-substrate so we can even out the high ammonium ion concentration.

Why are co-substrates used?

The addition of co-substrates is aimed to support microbial activity and growth which in turn improves the biodegradation of the substrate resulting into higher biogas production rates.

To achieve a better nutrient composition.

What are examples for co-substrates?

Manure can be a co-substrate for a silage based biogas plants (manure has higher content of nitrogen & buffering effect).
And crude glycerol as co-substrate for a silage can have a positive and stabilizing effect.

Furthermore: Considering its properties and composition, maize silage is often used in co-fermentation with other substrates, for example, with manure, sludge from wastewater plants, various plant substrates, or industrial wastes

Give an example of the necessity of micronutrients.
 

Methanogenic stage:
Co, Mo, and Ni, Se are Co-Factors for the Methane-Production

Name the composition of two substrates and their biogas yield.

>manure: high nutrient content, high organic matter concentration and high buffering capacity.
   ->e.g. manure derived from cattle yiels 45m^3/t - 60% methane content

>maize silage: high glucose content -> fast biol. pretreatment, low concentration of nitrogen, low buffering capacity.
   ->maize silage yiels 202m^3/t - 52% methane content


BTW.: maize silage as a single substrate is an unstable process due to the low alkalinity of silage that has to be compensated by pH adjustment.

The Stage of Hydrolysis in the Biogas Formation in one sentence:

A chemical/biological reaction where particulates are solubilized and large polymers converted into simpler monomers;
 

The Stage of Acidogenesis in the Biogas Formation in one sentence:

A biological reaction where simple monomers are converted into volatile fatty acids;
 

The Stage of Acetogenesis in the Biogas Formation in one sentence:
 

A biological reaction where volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen
 

The Stage of Methanogenesis in the Biogas Formation in one sentence:
 

A biological reaction where acetates are converted into methane and carbon dioxide, while hydrogen is consumed

Give an example for a microorganism producing proteolytic enzymes.

Aspergillus niger

What are the main energy sources in the past, in the presence and in the
future (1860 – 2060)?

ever since ever: Traditional Biomass
then: Coal (peak around 1910)
then: Oil, Gas (peak around 1970)
then: Nuclear Energy (no real peak, more like a plateau, start around 1940)
then: Renewable Energy (starting in late 1970)

What are the top six countries regarding the power capacities of renewable energy sources?

BRISC = Brazil, Russia, India, China, South Africa

EU

 

Give three examples for a zoonotic pathogen that can be transferred via manure.

Salmonella spp. can be transferred by many different manures.

E. coli can be transferred by cattle manures.

Yersinia enterocolitica can be transferred by pig manures.

What is co digestion biogas?

Codigestion refers to the simultaneous anaerobic digestion of multiple organic wastes in one digester. Codigestion is used to increase methane production from low-yielding or difficult to digest materials (i.e., feedstocks).

How is ammonia inhibitory?

Ammonia is a commonly encountered inhibitor in anaerobic digestion systems. Ammonium ion (NH4+) and free ammonia (NH3) are directly and indirectly inhibitory. Process inhibition is also related to the pH, temperature, and concentrations of ammonium and ammonia.

Inhibition of the biogas process by ammonia results in an enhanced accumulation of acetate and propionate. This leads to a decreased pH (due to the accumulation of acetate)

Higher reaction temeratures...

Lower reaction temeratures...

Which is are the options to prevent high inhibitory effects of Ammonia?

> pH adjustment

> dilution of batch medium

Which effect do high concentrations of ammonia have on the microbial comunity in a biogas plant?

The methanogenic bacteria die off

At which point in the biomass curve is it useful to work?

Which micronutrients are important for the production of ATP?
 

Which micronutrients are important for the H2 Uptake?

Which micronutrients are important for the CO2 Uptake?

Which micronutrients are important for the Acetate Metabolism?

Which micronutrients are important for the Uptake of Methylgroups?