Waste to energy technologies Flashcards

1
Q

Define embodied energy

A

collective sum of all the
energy required to produce any material, product or service

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2
Q

Describe what embodied energy is using the example of a brick

A

Embodied energy is the overall energy needed throughout a products life to make it usable these different stages are seen:
*Energy needed to extract the raw material to make the brick.
*Energy needed to transport the material to manufacturer
*Energy of the processes involved in the manufacture of the brick.
*Energy required for the transport to the building site.
 Energy used in putting the brick into place in the particular application.

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3
Q

What are the three measurements of embodied energy

A

Cradle to grave (whole life)
Cradle to gate (the extraction stage)
Cradle to site (energy used to the point of use of product)

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4
Q

How can we recover energy from waste

A

we burn waste to produce energy which is called incineration

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5
Q

4 Advantages of waste recovery through incineration

A

 Electric and energy generated from waste reducing demand for electric
from power plants, saving fossil fuel use & associated effects.
 Developments in incinerator technology have reduced significantly the
emission of harmful gases from the incinerator plants.
 Reduced the volume of waste to landfill, and therefore the demand for
new landfill sites. Landfills are becoming increasingly difficult to locate,
particularly in densely populated areas.
 Reduces the emission of LFG including methane and CO2 which would
otherwise be pumped into the atmosphere through landfilling.

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6
Q

3 disadvantages of waste recovery through incineration

A

 Still concern over the release of harmful gases into the atmosphere
through the incineration of waste.
 The ash residues must be disposed of which can be problematic as it
may in some cases be toxic.
 Local communities are generally opposed to the location of incinerator
installations in populated areas

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7
Q

Explain low solid in terms of anaerobic digestion

A

low solid digestion is where the feedstock is around 15% solid material

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8
Q

Explain residence time in terms of anaerobic digestion

A

The time taken for the full degration of the material in an aerobic digestion system

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9
Q

Explain high solid in terms of anaerobic digestion

A

High solid digestion is where the feed stock is around 55% solid material

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10
Q

Explain single stage in terms of anaerobic digestion

A

the biological reaction occurs in one holding tank and the biogas comes from this tank

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11
Q

Explain multistage in terms of anaerobic digestion

A

Hydrolysis, acetogenesis and acidogenesis occurs in one tank whilst the methanogenesis which produces the biogas occurs in a separate tank.

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12
Q

Name 8 different types of waste that can be treated by a compost heap

A

 Lawn clippings
 Shredded stalks
 Vegetable peelings
 Hedge clippings
 Cut flowers
 Teabags
 Leaves
 Egg shells

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13
Q

Explain why composting is unsuitable for treating any form of catering waste

A

cooked food cannot be put into composting bin as it will attract vermin and other animals and insects

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14
Q

Outline how anaerobic digestion can deliver both heat and power

A

Biogas from an AD plant can be burnt in a combined CHP plant, this generates
power (electricity) and heat.
Instead of losing the heat, as in traditional power plants, it is diverted into a local
heating system. This is co-generation.

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15
Q

what is anaerobic digestion and what gases are produced

A

This is when bacteria break down organic material into sugars then into various organic acids which are further decomposed to produce biogas. This biogas, is a mixture of
methane, carbon dioxide, and trace gases, including hydrogen sulphide

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16
Q

what are the 5 stages of anaerobic digestion

A

 mechanical pretreatment;
 hydrolysis;
 acidogenesis;
 acetogenesis; and
 methanogenesis

17
Q

how does anaerobic digestion result in biogas being produced

A

Hydrolysis takes place after mechanical pretreatment where insoluble polymers are broken down into organic soluble compounds. Then acidogenisis takes place where soluble organic compounds get fermented into volatile fatty acids. After this acetgoenisis takes place where alcohols and fatty acids are converted into acetic acid and
hydrogen. Finally methanogenisis happens where bacteria converts acetic acid and hydrogen into methane and carbon dioxide / biogas.