Solid Wastes What is Municipal Solid Waste (MSW)? The trash and garbage that comes out of our homes and businesses everyday How much solid waste do we generate? The average American generates approximately 4 lbs of solid waste per day How much solid waste do we generate? The average American generates approximately 1500 lbs of solid waste per year America generates more solid wastes than other industrial countries What is in our solid wastes? What is the composition of MSW? 1
Paper is the single largest category of material in MSW How do we dispose of MSW? Landfill Recycle How do we dispose of MSW? Landfill -- bury it -- burn it Recycle -- reuse it How do we dispose of MSW? How do we dispose of MSW? Landfill ~ 60 % ~ 15 % Recycle ~ 25 % How do we dispose of MSW in Missouri? 2
Landfill Myths We are going to bury ourselves in trash Landfill Myths We are running out of space for our trash Landfill Myths Most landfills have closed because they have filled up with trash The primary threat of landfills to the environment and human health is leachate What is leachate? A toxic liquid soup that forms in landfills as water mixes with chemicals in the wastes How is leachate a threat? Leachate can leak from landfills causing toxic contamination of ground and surface water 3
How is leachate a threat? the toxic chemicals can harm aquatic ecosystems How is leachate a threat? toxic chemical contamination of drinking water can harm human health Subtitle D of RCRA deals with solid wastes, including landfills New Subtitle D standards for landfills went into effect in 1994 Subtitle D design requirements are intended to reduce the threat of leachate bottom liner leachate collection leachate treatment 4
methane vents monitoring wells cover liner bottom liner a waterproof barrier between the trash and the soil bottom liner may be made of compacted clay or a special geotextile bottom liner purpose is to keep leachate from leaking out of the landfill leachate collection a grid of perforated pipes above the liner and below the trash leachate collection any leachate formed flows into the pipes and is pumped to the surface 5
leachate treatment leachate pumped to the surface is treated to remove or destroy the toxic chemicals methane vents methane is a flammable and explosive gas formed in landfills from anaerobic decomposition methane vents vents prevent methane build up in the landfill or escape from the landfill into nearby structures monitoring wells methane vents monitoring wells landfills can capture the methane and burn it as an energy source the landfill must be completely surrounded by monitoring wells 6
monitoring wells the purpose is to detect leachate leaking out of the landfill cover liner upon closure of the landfill, the wastes musts be covered with a waterproof clay cap cover liner the clay cap is to keep water out and minimize leachate formation Landfill Myth Materials in a landfill decompose like in a compost heap Actually, a modern landfill is more like an air-tight, water-tight tomb for our trash What are the pros and cons of landfills for management of MSW? -- Pros cheapest way to manage MSW low labor costs well established infrastructure improved design requirements 7
-- Cons do not solve waste problems, only leave the problems for future generations to deal with -- Cons create few jobs use large tracts of land N.I.M.B.Y -- Cons all landfills will eventually leak leading to environmental pollution -- Cons encourage a throw away society waste of natural resources -- Cons not consistent with a sustainable society How do we dispose of MSW? Landfill -- bury it -- burn it Recycle -- reuse it 8
disposes of MSW by combustion in mass burn incinerators not present in Missouri many MSW incinerators use the heat of combustion of wastes to generate electricity wastes-to-energy facilities wastes-to-energy wastes-to-energy development encouraged by OPEC oil embargo development also encouraged by PURPA wastes-to-energy Public Utilities Regulatory Policies Act Requires utilities to buy electricity from alternative (non-fossil fuel) generators 9
In the late 1970 s and early 1980 s it was predicted that waste-to-energy would become the number one method of MSW disposal in the U.S. burning reduces MSW weight and volume by 70 % -- 90 % what is left? ASH ASH from MSW incinerators concerns arose about the ash a long court battle ensued why the concerns arose about the ash? toxic chemicals in the ash toxic chemicals in the ash Combustion of MSW -- destroys some toxic organic chemicals toxic chemicals in the ash Combustion of MSW -- creates other toxic organic chemicals 10
toxic chemicals in the ash Combustion of MSW -- concentrates toxic inorganic chemicals in the ash toxic chemicals in the ash A long court battle developed over the ash The court battle was over how to classify the ash for disposal Industry argued that the ash was from MSW and should be classified as Subtitle D wastes -- Subtitle D wastes go to a standard landfill Governments and environmental groups argued that the ash should be classified as Subtitle C wastes because of toxic chemicals -- Subtitle C wastes go to a special hazardous waste landfill The U.S. Supreme Court finally ruled that the ash from MSW incineration must be tested for toxic chemicals 11
If found to be high in toxic chemicals, the ash must go to a Subtitle C hazardous waste landfill What are the pros and cons of incineration for management of MSW? - Pros waste-to-energy electricity reduces MSW weight & volume less land used for landfills - Pros destroys some toxic chemicals low labor costs recovery of ferrous metals - Cons toxic chemicals in ash disposal of toxic ash concerns about air pollution - Cons more expensive than landfills creates few jobs high costs of construction N.I.M.B.Y 12
- Cons competes with recycling encourage a throw away society waste of natural resources - Cons not consistent with a sustainable society How do we dispose of MSW? Landfill -- bury it -- burn it Recycle -- reuse it Recycling Collection of materials from MSW for processing and remanufacture into new products Recycling Much of our MSW can and should be recycled What recycles? paper metal glass plastic 13
What composts? yard wastes food wastes Recycling With relatively little effort on our part, recycling can reduce MSW by one-third 1500 lbs/yr X 1/3 = 500 lbs/yr Recycling With substantial effort, recycling and composting could reduce MSW by more than 80 % 1500 lbs/yr X 80 % = 1200 lbs/yr Recycling recycling rates vary by location in some areas 30 % or more of MSW is being recycled Recycling Recycling What are the pros and cons of recycling for management of MSW? 14
Recycling - Cons the most expensive method of MSW management -- often costs more than it pays Recycling - Cons very labor intensive -- many materials require manual sorting and processing Recycling - Cons can be a minor personal hassle -- changes in personal habits, storage, transportation, etc. Recycling - Cons recycling facilities not available everywhere -- often fewer facilities in rural areas Recycling - Cons Heavily dependent on market demand -- collected items are valueless unless there is a market for the items Recycling - Cons may cause loss of some jobs -- for example, mining for metals or cutting trees for paper 15
Recycling - Pros creates more jobs than landfills or incinerators -- even with some job losses, net employment increases Recycling - Pros only very minor behavioral changes required -- drop it in the recycling bin rather than the trash can Recycling - Pros some money can be earned -- many people turn in aluminum cans for money Recycling - Pros substantial savings in energy -- manufacture of goods from recycled materials takes less energy than from virgin materials Recycling - Pros substantial reduction in pollution -- manufacture of goods from recycled materials produces less pollution than from virgin materials Recycling - Pros conserves natural resources -- precious natural resources are reused rather than buried or burned 16
Recycling - Pros consistent with a sustainable society Recycling can be thought of the oldest and most natural form of recycling Matter in Ecosystems ABIOTIC BIOTIC matter continuously cycles through ecosystems is the managed decomposition of organic wastes What composts? yard wastes food wastes most food and yard waste can and should be composted composting could reduce MSW by 20-25% 17
several states, including Missouri, have banned yard wastes from landfills The biology of composting each compost pile is a small ecosystem with a complex food web The biology of composting Trophic Levels in Ecosystems carnivores Third Trophic Level herbivores plants top carnivores Fourth Trophic Level tertiary consumers Second Trophic Level secondary consumers primary consumers First Trophic Level producers Tertiary Consumers centipedes, predatory mites, flatworms Secondary Consumers springtails, some mites, some beetles, nematodes, rotifers Primary Consumers bacteria, fungi, actinomycetes, snails, slugs, earthworms, millipedes Organic Residues leaves, grass clippings, other plant debris, food scraps Organisms of the compost pile need food -- our organic wastes water -- needed by all life air -- O 2 for aerobic bacteria and other organisms 18
Food for compost organisms in the lingo or jargon of composting, the food (our organic wastes) can be divided into GREENS and BROWNS Food for compost organisms GREENS BROWNS -- are rich in nitrogen -- are rich in carbon Food for compost organisms the optimal C:N ratio is 30:1 however, an optimal ratio is not necessary for composting to occur Food for compost organisms GREENS -- are rich in nitrogen nitrogen is needed for metabolism and growth Food for compost organisms GREENS -- are rich in nitrogen good sources of nitrogen are green vegetation, vegetable and fruit wastes, manures also see the handout Food for compost organisms BROWNS -- are rich in carbon carbon is needed for energy 19
Food for compost organisms BROWNS -- are rich in carbon good sources of carbon are dried leaves, dried vegetation, paper, woody materials also see the handout water for the compost organisms the optimal moisture is about as damp as a wrung out sponge however, the optimal moisture is not necessary for composting to occur air for the compost organisms provides O 2 for aerobic organisms O 2 allows growth of aerobic bacteria and kills anaerobic bacteria air for the compost organisms aerobic bacteria decompose wastes rapidly and without odors anaerobic bacteria decompose wastes slowly and can cause foul odors air for the compost organisms the compost can be aerated by periodically turning the pile or by poking holes into the compost pile compost and temperature a well working compost pile heats up due to the metabolic activity of compost organisms 20
compost and temperature the warm temperature encourages the growth of thermophilic bacteria, the fastest decomposers compost and temperature the pile does not need to be warm for composting to occur, it will just take longer for complete decomposition of the wastes The compost pile the optimal size for a compost pile is approximately one cubic yard this is large enough to retain heat, but small enough for aeration to occur The compost pile the optimal size for a compost pile is approximately one cubic yard however, an optimal size is not necessary for composting to occur The compost pile many food wastes can be composted, including fruits, vegetables, cereals, coffee & filters, tea bags also see the handout The compost pile some food wastes should not be composted, including meat, cheese, dairy products, and grease also see the handout 21
The compost pile most types of yard wastes can be composted, including leaves, grass clipping, plant trimmings, many weeds also see the handout The compost pile highly invasive weeds and treated lumber should not be added to the compost pile also see the handout Finished Compost the process is finished when the material looks like dark, rich soil and no longer resembles the original organic wastes Finished Compost a rich, dark, crumbly humus called black gold by experienced gardeners Finished Compost Finished Compost composting makes a valuable resource out of organic wastes for free 22
Finished Compost a wonderful soil amendment improves soil structure improves water characteristics improves soil nutrients Finished Compost a wonderful soil amendment a slow-release fertilizer without pollution improves soil fertility improves plant growth and yield Finished Compost can be used as: a top dressing on lawns a mulch around trees & shrubs a seed starter a potting soil If you do everything right and work really hard at it You Get Compost COMPOST HAPPENS! If you do everything wrong and don t work at it at all You Get Compost COMPOST HAPPENS! What s the difference? the length of time 23
If you do everything right and work really hard at it You Get Compost in 4 6 weeks COMPOST HAPPENS! If you do everything wrong and don t work at it at all You Get Compost in 1 2 years COMPOST HAPPENS! 24