Chapter 3 - Waste To Energy Technologies Flashcards
What is meant by embodied energy
Embodied energy is the name given to the collective sum of all the energy required to produce any material product or service
What are the advantages of incineration of waste
Reduces volume of waste sent to landfills
Incineration plants can generate lots of electricity and can also provide local district heating
Energy from waste reduces the amount of landfill tax that has to be paid
Bottom ash residue may be recycled for building materials
What are the disadvantages of incineration of waste
There is a negative public opinion on the emissions of gases
Residue from flue gas treatment or bottom ash may go to landfill as hazardous waste
Plants are costly and need high utilisation to be cost effective
Risk to supply due to export to countries with lower gate fees
Risk to supply due to legal activity regarding gate fees
What is low solids in anaerobic digestion
Low solid digestion is where the feedstock is around 15% solid material
What is high solids in anaerobic digestion
High solid digestion is where the feedstock is around 55% solid material
What does residence time mean in anaerobic digestion
The time taken for full degradation of the material in an anaerobic digestion system
What does single stage mean in anaerobic digestion
The biological reactions occur in one holding tank and the biogas comes from this tank
What does multi stage mean in anaerobic digestion
Hydrolysis, acetogenesis and acidogenesis occurs in one tank whilst the methanogenesis which produces the biogas occurs in a seperate tank
Explain how anaerobic digestion results in the production of biogas
Hydrolysis - Insoluble polymers broken down to soluble organic compounds
Acidogenesis -Soluble organic compounds fermented into volatile fatty acids and alcohols
Acetogenesis - Alcohols and fatty acids converted into acetic acid and hydrogen
Methanogenesis - Bacteria convert acetic acid and hydrogen into methane and carbon dioxide or biogas
How can anaerobic digestion produce both heat and power
Biogas from anaerobic digestion can be burnt in a combined CPH plant which generates power and heat
Instead of losing the heat as in traditional power plants it is diverted into a local heating system
Name 5 types of organic waste
Lawn clippings
Vegetable peelings
Egg shells
Tea bags
Leaves
Why is composting unsuitable for treating any form of catering waste
Cooked food cannot be used as it will attracts rats or other vermin
