Biotechnological Conversion Processes

Hydrolysis

Acidogenesis

Acetogenesis

Methanogenesis

The most promising dry fermenter in research is the DRANCO. 

DRANCO characteristics:

• vertical fermenter: feeding at the top and extraction through a conical outlet at the bottom

• single-phase digestion with intensive recycling of the digestate

• thermophilic or mesophilic operation

• compact, well-insulated digesters with minimal heating requirements

• high-rate dry digestion (very high loading rates and biogas productivities can be achieved)

Profi said “DRANCO has a high potential because the produced biogas and the effluent go in opposite directions.”

1. Bioenergiedorf: New concept in Germany since 2017
2. Biomass power plants: cogeneration with wood (wood chip heating)
3. Swine waste energy
4. Cryogenic separation
5. New laws: EEG (Renewable Energy Source Act)

From the slides:
- Reduced burden on fossil fuels

- Environment pollution abatement

(...)

- Renewable source of energy

(...)

- Forest protection and GHG emission reduction

Yes, fossil fuels used for transport of substrate to the plant

- emission of greenhouse gases when substrate is transported long distances

….But regarding effect of biogas plants on the existent climate crisis:

- Reduces burden on forests and fossil fuels.

- Produces a clean fuel - helps in controlling air pollution.

- Agricultural waste management and energy generation in an anaerobic digestion framework which is not a contribution to climate change but a mitigation 

- Controls water pollution through anaerobic digestion implementation.

Bioenergiedorf” - Many villages in Germany
- Over 50% of the systems are owned by heat consumers and farmers

The costs associated to producing biogas vary. In the developed world, the price of producing biogas is comparable to the price of producing natural gas. Varying costs are given by different sources, varying from approximately £1.25 up to £4.50 per 1,000 m3.

 - Reduced burden on fossil fuels

- Environment pollution abatement

- Improvement in yields of agriculture products

- Renewable source of energy

- Comprehensive use of biomass technology

- Innovation and technology

- Forest protection and GHG emission reduction

- costs of a biogas plant

costs of obtaining substrates together with transportation

- maintenance and repair

- taxes

- salary costs

- other (extra protection of the object, carrying out physical, and chemical analysis)

Bioethanol is an alcohol made by fermentation of carbohydrates produced in sugar and starchy crops.

Four major unit operations:

Pretreatment -> Hydrolysis -> Fermentation -> Destillation

The bioethanol production relies on several processes: corn-to-ethanol, sugarcane-to-ethanol, basic and integrated lignocellulosic biomass-to-ethanol. The raw materials undergo several pre-treatment steps and then enter the fermentation stage where bioethanol is produced.

ToDo: Bioethanol production process steps in detail

• good source of alternative fuel production and high potential for utilization in the market.

• good  approach for biofuel innovation and optimization.

• leading to a cleaner environment and energy-savings.

ToDo: check if anything missing!

ToDo: Sufficient?

the problem of efficient lignocellulose hydrolysis to sugars occurs during fermentation.

- lignocellulose pretreatment is an indispensable step.
  ->main aims of the pretreatment:
        > disintegration of a tight structure of lignocellulosic complexes
        > increase in the accessibility of various hydrolytic factors towards cellulose

However during (thermal) pretreatment aromatic (/phenolic) compounds can be freed that have an inhibitory effect

Research on Consolidated Biomass Processing (CBP):
- Clostridium and Rumen bacterium
- C. thermocellum in combination with other thermophiles

Biorefinery is created for efficient processing of biomass coming from plant, livestock byproducts and wastes into energy, fuels, chemicals, polymers, food additives.

• The main fraction of worldwide energy carriers and material products, especially chemicals, is derived from fossil fuels, mainly oil and natural gas.

• But …

... the expected price of fossil resources increases

... the environmental impacts from fossil fuels are serious

• A need to increase and develop renewable energy generation

• High amount of biomass/waste to be managed

Technological Innovation: Immunotherapies, Enzymes for medicine, Industrial bioeconomy

Social Innovation: Local energy grid communities, Ecovillages, Urban gardening

Organizational & Political Innovation: Establishment of international platforms for a continuous and open dialogue between scientists, policymakers, companies, and citizens

Microbial Fuel Cell (MFC) is a technology, which uses microorganisms to catalyze the direct generation of electricity from organic matter. It provides a completely new approach for energy generation from wastes.

• Nowadays, the main drawback for the full-scale application of MFC is the cost of materials and the low buffering capacity of domestic wastewater. For this reason, there is no industrial application of MFC to date. Other limitations; durability, size and weight, thermal and water management

From slides:

• Power generated by the cell may not be enough to run a sensor or a transmitter continuously.

• It can be solved by increasing the surface area of the electrodes or by transferring the data only when enough energy is stored by an ultracapacitor (this resembles a suitable power management program).

• MFCs cannot operate at extremely low temperatures due to the fact that microbial reactions are slow at low temperatures.

MFCs have different applications based on power generation.

The generated power in MFC is still too low and researchers are working to improve it for commercial application.
 

• generation of bioelectricity

• biohydrogen production

• wastewater treatment

• MFC in biosensor

“Mass going in the same as mass going out + the production of dynamics that have to be considered.”

-> controlling different moments of the cell mass distribution using cell population balance modeling.

The mathematical term describing the dynamics of the cell mass distribution, substrate concentration and product is

A=T+R with 

A modeling the accumulation, 

T being the transport term, and 

R modeling the reaction rate.

The wash-out rate, i.e. the rate at which organisms initially present in the vessel would be washed out if growth ceased but flow continued is therefore: −dx dt=Dx

Washout occurs at a high enough dilution rate that the cells are flushed out of the reactor.

The dilution rate is defined as the flow of medium per unit of time, F, over the volume V of culture in the bioreactor.

The wash-out point is the point at which the max growth rate is met and organisms present in the vessel would be washed out if further dilution was happening. The growth does not increase as it is at \({\mu}_{max}\)  so if the flow continues washout occurs. Hence at a high enough dilution rate the cells are flushed out of the reactor.

The critical dilution rate is the value of dilution rate at which the steady-state Biomass concentration just becomes zero.

We want to work at dP/dD=0 and at the critical dilution rate we have F/V=D_crit=μ_max with F the flow rate and V the volume. We have the highest productivity at the critical dilution rate and the best substrate conversion ratio. The effectiveness of substrate conversion rapidly declines after D_crit.