What are the disadvantages of a waste to energy plants?

Answer 1

Biogas plants in the form of Anaerobic Digestors accept substrates normally comprising biological waste including: sewage sludge, food waste, municipal waste, agricultural waste and energy crops. The plant uses a series of naturally occurring chemical and biological processes to reduce pathogen count in the sludge and generate biogas. The output from the plant comes in the form of biogas and digestate. If the process meets the relevant local regulations then the digestate can be used as fertiliser. The biogas prinicipally comprises methane and carbon dioxide with a number of other contaminants including hydrogen sulphide, siloxanes and moisture.

Biogas is commonly used in its raw form as a fuel for a gas boiler or combined heat and power engine since the anaerobic digestion plant itself needs a heat supply. The biogas is sometimes upgraded by stripping the other gases to leave a purified biomethane.

There are a few disadvantages of biogas and these include:

- The process of digestion reduces the total solids content in the sludge and thus there is a volume loss of the organic waste compared to composting, however both can produce a fertiliser;

- Biogas contains contaminant gases which can be corrosive to gas engines and boilers;

- Digestate must meet high standards in order to be used on land without detrimental effects on agricultural uses especially food crops;

- Biogas plants and gas upgrading plants both have a relatively high heat and energy demand which demand some of the biogas produced to be used on-site;

- Will only produce a limited quantity of energy demand and is dependant upon location in proximity to feedstock and energy users;

- There is little or no control on the rate of gas production, although the gas can, to some extent be stored and used as required.

There are also a few advantages of biogas:

- Produces a renewable fuel that is flexible and can be used to produce heat, power, domestic gas use or as a vehicle fuel;

- Waste is captured and used to generate energy and a useable by-product in the form of digestate for fertiliser;

- Generates methane that can be captured and used to produce energy that might otherwise leak into the atmosphere and increase the greenhouse effect;

- The process fixes nitrogen in the digestate and reduces emissions of nitrous oxide (a strong greenhouse gas) compared to composting or landfill.

- Biogas plants work at a range of scales, e.g. domestic plants in India and China, through pig, dairy, beef farms up to municipal and industrial waste facilities.

- Biogas can be upgraded to biomethane and transported to where energy is demanded.

Answer 2

these involves poisonous chemicals so they are health hazards

Answer 3

it is not cost or energy efficient it also produces methane gas witch can be dangerous the amount of energy that it produces is the same amount that it takes to process it.