Waste

Lecture 16 SCI250

Trash Stats

• Average American (Canadians are probably similar) generates 4lbs (2kg) of trash per day
• Packaging is ~65% of household trash
• Average college student produces 640 lbs of solid waste per year, including ~500 disposable cups and 320 lbs of paper
• North America has 8% of the world’s population but produces half of the world’s nonorganic trash
• Most communities are spending more on waste management than schoolbooks, fire, libraries and parks
• In USA: Household, industrial, agricultural, mineral waste
  • 4 billion tons of solid waste (~800,000,000 Elephanst)
  • 40 billion gallons of sewage wastewater per year (~80,000 Olympic pools)

Type of Waste

Waste

Any unwanted material or substance that results from human activity or process.

1. Municipal solid waste = non-liquid waste that comes from homes, institutions, and small businesses
2. Industrial solid waste = waste from production of consumer goods, mining, agriculture, and petroleum extraction and refining
3. Hazardous waste = solid or liquid waste that is toxic, chemically reactive, flammable, radioactive, or corrosive
4. Wastewater = water used in a household, business, or industry, as well as polluted runoff from our streets and storm drains

Overview:

• Solid waste
• Municipal waste disposal
• Reducing solid waste volume
• Toxic-waste disposal
• Sewage treatment
• Radioactive waste

Major sources of solid waste in USA & Canada

• Agriculture: crops and animals; more than 50% of solid waste
• Mineral industry: spoils, tailings, slag, other rock/mineral waste; major source
• Other industry: highly toxic; minor compared to others
• Municipalities: very visible; minor compared to others

Solid Wate - Agricultural

Over half our waste is from agriculture:

• Animal production - manure, bedding
• Food and meat processing - bits we don’t eat
• Crop production - harvest waste
• Horticultural production - landscaping
• Industrial agricultural (e.g., wood processing)
• Chemical wastes - herbicides, pesticides

Solid Waste - Mining

In Canada, mining waste >30 times that from household + municipal + industry

• 1 ton of iron $\Rightarrow$ 3 tons of waste
• 1 ton of copper, nickel, zinc, lithium or graphite $\Rightarrow$ 20 to 200 tons of waste
• 1 ton of platinum group elements, rare earth elements, or gold $\Rightarrow$ more than a million tons of waste

But waste can be valuable: Conservative estimate of ~$10 billion in total metal value remains in Canada gold mine waste.

Solid Waste - Industrial

Industrial waste NOT from mining:

• Together all of this is only a few percent of the total mining and agriculture waste
• Chemicals > paper > food

Municipal Waste

How to dispose of municipal waste?

Three options:

1. Landfills
2. Incinerate
3. Compost/Recycle

Municipal Waste Disposal

Open dumps: easy and cheap method

• But are gross, smelly, attract animals, are fire hazards, leach chemicals, and erode
• Illegal in USA since 1976 but hundreds of thousands still operating
• Main source of disposal in much of developing world

Sanitary Landfills: compacted trash is laid down and covered by layer of soil each day

• Most municipal waste disposed of this way
• Use valleys or abandoned pits or surface mines
• When full, covered by thick layer and repurposed
  • Parks, pasture, parking lots, ski hills, golf courses, solar
  • Nothing that needs to be excavated to build

Waterloo Landfill (across from Costco)

• Opened in 1972 and is only operating landfill in Waterloo Region
• 126 hectares and includes recycling facility
• Expected to reach capacity in 15-20 years

Landfill Gas

• Oxic: $C{O}_2$ and $S{O}_2$; Anoxic: $C{H}_4$ and $H_{2}S$
• Usually vented or burned off
• $C{H}_4$ captured for natural gas

More than 40 operational projects in Canada collect landfill gas and convert it into energy.

Leachate

Water containing dissolved chemicals from landfill can contaminate ground/surface water

• Problems in old landfills without impermeable layering at bottom
• Or problem if water table reaches base of landfill
• Now we build over bedrock or low permeable layers or line with impermeable material or clay
• To avoid spillover to surroundings (‘bathtub affect’) must not allow accumulation of leachate in landfill
  • Build with low permeable layers below and above landfill
  • Can pump out leachate or use plants to take up chemical-laden water (but not for crops)

Proper sanitary landfilling is complex

Landfills requires space

• Rule of thumb: One acre (half a soccer pitch) filled 3m deep per year for 10,000 people
  • Toronto: 6,255,000 people $\Rightarrow$ 625 acres or > 300 soccer pitches
• USA produces 250 million tons of trash PER YEAR
  • About 50,000,000 elephants
• Most sites were opened in 70s & 80s
• Harder to find new sites
  • NIMBY - not in my backyard
  • NIMFYE - not in my front yard either
  • NIMEY - not in my election yaer
  • NOPE - no on planet earth
• People: landfill ration increasing

Incineration

• Solves space issue but releases pollutants
  • Everything $\Rightarrow C{O}_2$
  • Plastics $\Rightarrow$ chlorine gas, hydrochloric acid, hydrogen cyande
  • Organic matter $\Rightarrow S{O}_2$
• Technology has improved
  • Higher temperatures breakdown complex organics into just $C{O}_2$ and $H_{2}O$
  • But toxic elements like mercury or lead may still be released
• Only combustibles should be burned, like paper and wood, and can be used as a source of heat
  • Many countries adopted this practice and growing in popularity elsewhere

Ocean dumping

• Used to be popular (80% of NYC trash went into oceans and lined the shores)
• Still done to some degree either after incinerating or without burning, but has waned
• Hazardous chemicals often treated this way
• Banned sewage and industrial waste dumping in USA in 1991
• Dredge spoils (sediments dredged from reservoirs and waterways)
  • Still allowed to dump $\Rightarrow$ 200 million tons/year
  • Pollutants very possible

Reducing Solid-Waste Volume

• Try other ways to reduce waste first
• Disposal is last resort
• Compaction helps reduce volume, but…
  • Lose anything recoverable
  • Slows organic matter decomposition, which is already slow in dry landfills

Organic Matter

• Composting household and yard waste produces fertile soil
• USA - 60% of yard waste is composted
  • Household waste - by individuals mostly
• Some towns and countries compost on a municipal level

Recycling Glass

• Glass can spend a million years in a landfill
• All provinces, except Nunavut and Ontario only alcohol

Recycling Paper

• One of easiest to recycle but best when single type
• Saves landfill space, trees, water, and energy (i.e., gasoline)

Recycling Rates

• USA – 65% of all paper
• Canada – 25% of all paper
• Both countries recycle 85-90% of their cardboard

Recycling Plastic

• Plastics are durable and breakdown only at high temperatures
• Most plastics marked with symbol for easy separation
• Not often used for same product after recycling
  • Repurposed into piping, stuffing for upholstery, carpet fiber, trash bags, plastic lumber
  • More research into other uses – pillows, clothing, fiberglass

• Construction and demolition debris (concrete, asphalt, metal) can be repurposed in new construction
• Waste exchanges, e.g., Canadian Waste Materials Exchange, supports the exchange between states, provinces, companies
• E-waste/E-cycling – electronics have toxic elements (lead, cadmium, mercury)
• Mostly goes to South and East Asia

Toxic-Waste Disposal

• Toxic-waste is often liquid
  • Concentrated, highly-toxic by-product of industry

Previous Methods

• Dilute-and-disperse: belief that toxins are less toxic when dilute
  • E.g., ocean dumping
  • Not the case with many chemicals and bioaccumulation in food chain likely
• Concentrate-and-contain: leads to disasters
  • Buried in pits or trenches or metal/plastic boxes in landfills
  • Example, Love Canal, New York: near Niagara Falls

Secure Landfills

• Hole lined with plastic and/or clay
• Toxic waste in drums
• Wells drilled for monitoring
• But they still do leak

Deep-Well Disposal

• Need porous and permeable rock (e.g., sandstone or fractured limestone) bordered by low-permeability layers (e.g., shale)
• 100s to 1000s m deep, below water table
• Assume lateral movement is so slow that chemical will be diluted by the time it reaches an aquifer
• Costs similar to secure landfill but sites are more limited
• Earthquakes can happen

Other types

• Furnaces to burn it
• Chemical treatments
• Waste exchange

Sewage Treatment

Need to treat our wastewater before it mixes with surface or groundwater

• Why? Prevent oxygen depletion, algal blooms, and spread of pathogens

Septic Systems

• Solids settle in tank

• Liquid seep into leaching field (soil adsorption field) where organic matter and some pathogens broken down by microbes

• Chemical and particulates filtered out and broken down

  

Geologic requirements for a septic system

• Soil must have certain permeability
• Water table must be well below
• ~60 cm of topsoil and 150 cm below
• Not within 15 m of surface water

Size requirement for a septic system

• Size determined by soil permeability and number of people using it
• Determined by city
• Not suitable for high population densities

Municipal Sewage Treatment:

1. Primary is physical treatment
2. Secondary is biological treatment

• These stages reduce solids and DOM by 90%, N by 50%, P by 33%

3. Tertiary is costly and uncommon (few % in USA)

Waterloo Region has 13 wastewater treatment plants that process 155 million liters of water per day (~3600 swimming pools)

Treated sewage water can be used

• Drinking water
• Irrigation
• Recharge marshes or ponds
• Fish hatchery
• Recharge geothermal reservoir

Sludge needs to be dealt with

• Fertilizer for parks, athletic fields, golf course, but not crops
• Landfilled
• Burned

Global average: 52% of sewage treated but heavily varies. In some countries, 90% ends up in surface water.

Radioactive Waste

• Radioactive isotopes with half-lives of years to 100s years are most dangerous
• Long or short half-lives are usually not (e.g., U-238 @ 4.5 billion years)
• Unless toxic, like Plutonium-239 (24,000 years), or they are concentrated naturally in our own systems:
  • Iodine-131, 8 days, in thyroid gland
  • Iron-59, 45 days, hemoglobin in blood
  • Cesium-137, 30 years, nervous system
  • Strontium-90, 29 years, bones, teeth, milk

• 86-90% of radioactive waste is low level and taken care of on-site or at a containment facility
• Released to environment or landfills when radiation levels are low
  • E.g., gases, liquids from laundry or cleaning, solids from fibers
• Remaining 10% is high level radioactive waste and is the hazard
• Spent (used) fuel (also called fuel rods) and by-products of fabrication and reprocessing are the biggest sources of radioactivity

Nuclear ‘fuel’ is made of ceramic pellets of enriched uranium that are packed into metal rods

USA has a total of 83,000 metric tons of spent fuel in 76 sites in 34 states

• Can fit in one football field (90x50m) to a depth of 30ft (10m)
• USA would have the most spent fuel that needs to be stored based on country-specific production

Historical suggestions:

• Rocket into space with a (hopefully) successful launch
• Melt its way into Antarctic ice and be covered again by ice
• Carried to mantle via subduction in a seafloor trench
• Sinking them into stable clays of the deep-sea floor*
  • *Was being looked into the most in the 1980s but nothing since

Liquid High-Level Waste

• Currently stored in cooled underground tanks that leak
• Hanford facility in Washington state
  • 50 million gallons, of which 1 million has leaked into Columbia River and costs $2 billion per year to remediate
• Caverns in low-permeability, unfractured igneous rocks better option
  • But cannot guarantee the geologic stability of the rock and liquids migrate
  • Solidifying the liquids then storing this way is what is being considered

Solid High-Level Waste

• Multiple barrier concept in a secure bedrock formation
  • Granite: strong, table, low porosity, insoluble minerals but can fracture
    • USA, Sweden, Finland, Switzerland and Japan testing granite
  • Thick basalts: strong when fresh and unfractured, can withstand and disperse heat, but can contain porous zones and weathers easily
  • Massive deposits of tuff – from past pyroclastic volcanic eruptions
  • Shale or other clay-rich sedimentary rocks – adsorb well, low permeability, but fracture readily and decompose at elevated temperature
  • Salt – high melting point, low porosity and permeability, flows plastically, but would need to be in a dry environment