2 Flashcards
Briefly describe the waste minimisation hierarchy
The options for waste management are often arranged in this hierarchical manner to reflect their desirability. The aim of the hierarchy is to extract the maximum benefits from materials whilst generating the minimum amount of waste.
The first priority is waste prevention or reduction – that is, not producing the waste in the first place. If waste is produced then this should be minimised. The next priority is maximising reuse or recycling and recovery of suitable waste materials. Once the possibility of waste prevention have been exhausted then the next option is treatment, to reduce the volume of waste, to neutralise or render the waste harmless, to extract resources in the form of products and/or energy. The final option – and least desirable - is to dispose of the waste either to the air, water or land.
A circular economy is one that exchanges the typical
A circular economy is one that exchanges the typical cycle of make, use, dispose in favour of as much reuse and recycling as possible. The longer materials and resources are in use, the more value is extracted from them. This could contribute toward reducing Europe dependence on critical materials such as cobalt, fluorspar or gallium, but also reduce overall demand by recovering the resources, nutrients or energy contained in products at the end
of their useful life.
Extending the life of products and materials
prevents the over generation of waste and recovers the full value of products. This would create new business opportunities and revenue streams, while minimising the environmental impact of mining, resource extraction, refining and manufacture.
Ways to achieve waste avoidance/minimisation
1- Product design change:
Product design with less waste
Increase product life
2- Package change:
Reusable or recyclable pack, concentrate
3- Materials change:
Substitution of less toxic materials
4- Technological change:
Improved/more efficient equipment
5- Management practices:
Good housekeeping, inventory control
Solid waste hazards
- Human pathogens
- Insects & rodents
- Animal pathogens
- Leaching
- Odour
- Soil pathogens
Sources and types of solid waste
- Domestic:
Food
Paper
Packaging
Glass
Metal
Ashes
Bulky household waste
Hazardous household waste - Commercial:
Food
Paper
Packaging
Glass
Metal
Ashes
Bulky household waste
Hazardous household waste - Industrial:
Industrial process wastes
Metals
Lumber
Plastics
Oils
Hazardous wastes - Construction and demolition:
Soil
Concrete
Timber
Steel
Plastics
Glass
Vegetation
- Explain duty of care with respect to solid waste.
Industry and other businesses have a duty of care when it comes to waste. This means that the producer’s responsibility for waste does not end at the factory gate. This duty is placed on anyone who imports, produces, carries, keeps, treats or has control of waste (this excludes domestic waste).
Waste management legislation
2008 EU Waste Framework Directive
2011 Waste (England and Wales) Regulations
2007 Environmental Permitting Regulations
2010 Industrial Emissions Directive (IED)
Permit authorises treatment, keeping or disposal of controlled waste in
or on specified land
1996 Special Waste Regulation
2005 Hazardous Waste Regulations
Waste minimisation hierarchy applied to solid
waste
- Reduction at source: Don’t produce it in the first place!
- Recycling/reuse: Recycling
- Treatment: Biological, Combustion, Gasification
Pyrolysis (With/without Energy recovery) - Disposal: landfill
Chemical and energy properties
- Proximate analysis:
Moisture content
Volatile matter
Fixed carbon
Noncombustible fraction (ash) - Ultimate analysis
Carbon
Hydrogen
Oxygen
Nitrogen
Sulphur
Ash - Energy content MJ/kg
Solid waste treatment options
1- Recycle
2- Biological
*Composting or aerobic
*Biogas or anaerobic
* Combined aerobic and anaerobic
3- Thermal
*Combustion
*Gasification
*Pyrolysis
* Energy from waste
4- Landfill
Recycling example
Paper & cardboard
Glass
Aluminium cans
Plastics
Textiles
Batteries
Plus lots more!
what is Biological treatment
Used to treat the organic fraction of waste
Reduces volume
Valuable products/energy
Waste becomes inert
3 options:
Aerobic composting
Anaerobic to generate biogas
Combined anaerobic and aerobic
for Composting what are the process parameters
- Temperature
- Moisture content
- Oxygen
- C/N ratio
- pH
- Biochemical composition and texture
Composting systems
Windrow
In vessel
Aerated static pile
Issues with composting
- Heavy metals
- Odour
- Sterilisation
- Inert contaminants
Anerobic digestion process parameters
- Oxygen free
- Stages
*Hydrolysis
*Acidogenisis
*Methanogenesis
-Temperature control is important
- Biogas can be used as a fuel
AD examples
GWE Biogas Ltd
*50,000 tonnes organic waste
*Local authorities, food manufacturers
and supermarkets
*Generate 2 MW electricity for export to
grid
Staples Vegetables
- Out of spec vegetables
- Electricity used on site or exported to grid
- Excess heat used to heat offices and buildings
Thermal treatment types or options
- Incineration (combustion)
- Gasification
- Pyrolysis
( Waste to energy)
Incineration process parameters
*Complete oxidation at high temperature
*Organic material is converted into heat, flue gas
and ash
IED sets stringent requirements:
*Minimum combustion temperature 850 C
for 2 seconds
*Specific emission limits for SO 2 , NO x , HCl,
CO, Total Organic Carbon (TOC)
*Ash to have organic carbon content < 3%
*Thermal efficiency up to 80- 90%
*Electricity generation ~ 27%
Incineration technology
Moving grate (most common type)
Fixed grate
Fluidized bed
Rotary kiln
Main factors that influence emissions from waste incinerators:
*Composition of the waste
*Combustion control
*Mechanical processes
To control emissions:
*Combustion conditions for CO, VOCs and dioxins
*Ammonia injection for NO x
*Lime injection for SO 2 and HCl
*Carbon injection for capture of heavy metals
*Filter system for fly ash and other solids
Gasification process parameters
*Thermal decomposition in the presence of a controlled amount of oxygen and/or steam
*Process occurs at high temperature (> 700 C)
*Produces syngas (carbon monoxide, hydrogen and some carbon dioxide)
*Gas can be used directly in engines to generate electricity
Gasification equipment
- moving bed gasifier
- fluidized bed gasifier
- entrained flow gasifier
what is Pyrolysis
Thermal conversion of waste in the absence of oxygen
what are Pyrolysis types and products
Three types:
-Slow
-Intermediate
- Fast
Products:
*Pyrolysis liquid
*Char
*Gas
Landfill random facts :)
*Last resort
*UK running out of landfill capacity
* Most landfill sites control and collect gas
what is our biggest waste challenge?
What can we do? as As individuals, and As engineers?
plastics
As individuals
*Reduce consumption
*Reuse /recycle
As engineers
*New ways to re use plastics
*Develop biodegradable plastics
*Improve plastic recycling processes
*Reduce the amount of plastic used in processes
A farmer is interested in developing an energy from waste plant to deal with the farm’s organic waste. What are the options? What would you recommend and why?
There is no single correct answer to this question. You should present the options available with a short description of each, with advantages and disadvantages. Then choose and justify a process for the farm’s organic waste
