Biogas

What is acetogenesis?

Acetate production, beta oxidation. Conversion of all built substances into acetate, hydrogen and carbon dioxide. The anaerobic bacteria have no tolerance for oxygen

What are the two paths of methanogenic reaction?

Acetoclastic (methane results from sewage sludge stabilization) and hydrogenetroph. Both are exergonic reactions

How can H2S be removed?

Can be removed biologically, physically and chemically

What does CHP mean? What are the main components?

Combined Heat and Power plant: made of combustion engine, generator and heat exchanger

What are the steps of gas cleaning and treatment?

Desulphurization Biological - adding H2S carbon dioxide and nutrients Chemical adding FeCl2 and H2S physical - adding activated carbon, membranes Drying Condensation drying (easiest) Adsorption drying Absorption drying (glycol washing)

What are the process variants?

Dry substance and wet fermentation (wet is dominant in germany) Single or multilevel. Level refers to number of heated fermenter Temp: psychrophilic, mesophilic or thermophilic (mesophilic temp is dominant in germany) Continuous vs non continuous feeding. Non continuous: fermenter is filled once and closed air tight, vaccination material stays inside. No constant gas production and quality. Good because there is an exact dwell time. Continuous: flow through process and feeding is done several times a day, fermenters are always filled. Continuous gas production but bad because of methane emissions

What is acidogenesis?

Follows hydrolysis even though there is no real separation between the two stages; unspecific acid production and first energy gain of facultative anaerobic microorganisms; acidification phase

Talk about energy waste water

Great potential, bio energy from waste water. Ideally german buildings could be heated from wastewater in sewer systems. Heat = energy can be utilized by extracting it from wastewater by using a heat pump

What are the steps of biogas production?

Hydrolysis, acidogenesis, acetogenesis, methanogenesis

Why is hydrogen sulfide problematic?

It is toxic for all living things in great amounts, it can lead to corrosion.

What are the two main components of biogas?

Methane and carbon dioxide. Also hydrogen sulfide, nitrogen and oxygen

Explain the disintegration step:

Not technically a real step of anaerobic digestion. If you have polymer substances which are very stable then it may take awhile to hydrolyze them. Solution is upstream disintegration.

What is FOS/TAC?

Proportion between volatile fatty acids and buffer capacity and describes biochemical condition of plant. Important to look at the changes OF THE fos. When 0.3-0.4 it's good, if less than hungry and if more than overfed

What are enzymes?

Reduce the activation energy needed; surface catalysts; reactions take place on the enzyme surface

What is methanogenesis?

Reduction of carbon dioxide to CH4 coupled with ATP synthesis by electron transport. The products from acetogenesis and acidogenesis are turned to CH4. This is the energy providing step and done only by archea. Methanogenic archaea are unicellular anaerobes (prokaryotes)

What is hydrolysis?

Splitting phase, dissolution by water; splitting of complex compounds into smaller elementary monomers. Presence of ENZYMES

Biogas plant four step process:

Substrate management, biogas production, fermentation residue storage, treatment and use, finally biogas storing treatment and use

What factors influence the archaea?

Temperature, pH level and presence of oxygen