Waste to Energy Technologies Flashcards
Explain the term Low Solids.
The feedstock is around 15% solid material.
Explain the term High Solids.
The feedstock is around 55% solid material.
Explain the term Residence time.
Time taken for the degradation of the material in an AD system.
Explain the term Single-Stage.
All biological reactions occur in one tank and the biogas comes out.
Explain the term Multi-Stage.
Hydrolysis, acetogenesis, and acidogenesis all occurs in one tank whilst the methanogenesis occurs in a separate tank.
Outline how AD can be used to provide both heat and power.(CHP)
Biogas from AD can be burnt in a CHP plant to generate power
(electricity) and heat[1]
Instead of losing heat, as in traditional power
plants, its diverted into local heating systems. [1]
Name 3 types of waste which can be composted.
Lawn clippings.
Veg Peelings
Tea bags
Explain why composting is unsuitable for treating any form of catering waste.
Cooked food must never be used in composting because it will attract vermin.
Describe the concept of embodied energy.
Name of the collective sum [1] of all the energy
required to produce any material, product or service. [1]
Identify stages A & B
mechanical pre-treatment A acidogenesis B methanogenesis
A: Hydrolysis. [1]
B: Acetogenesis. [1]
Explain what happens during the acidogenesis and methanogenesis
stages associated with anaerobic digestion.
Acidogenesis: soluble organic compounds are fermented [1] into volatile
fatty acids and alcohols. [1]
Methanogenesis: the bacteria convert acetic acid and hydrogen [1] into
methane and carbon dioxide – biogas. [1]
Explain what is meant by the term embodied energy.
Embodied energy is the name given to the collective sum of all the energy required to produce any material, product or service. [2]
Discuss one advantage and one disadvantage of waste incineration. (4)
Electricity and heat can be generated from sources other than fossil fuels which may contribute to their conservation. [2]
D: There is still concern over emissions from incinerators despite the technological developments. [2]
Explain how anaerobic digestion can be used in conjunction with CHP. (2)
Biogas from an anaerobic digestion plant undergoes combustion at a CHP plant to generate power (electricity) and heat. Instead of losing the heat, as in traditional power plants, it is diverted into local heating systems.
With reference to anaerobic digestion, state the term used to mean:
The time taken for the full degradation of material in an anaerobic digestion system:
Residence Time.
