Solid Waste Collection

Objective(s): To describe the tasks and logistics of MSW collection, to analyze collection systems, and to become familiar with the principals and theory behind the use of transfer stations

Goals:

Understand problems and concerns associated with MSW collection.
Compare and contrast privately and publicly operated systems.
Understand the types of collection systems
To identify the benefits associated with the use of transfer stations
To prepare an economic analysis of transfer stations
To understand the design issues associated with transfer stations

General Information

Collection accounts for 50-70% of a SW budget!

Types of Collection System

Refuse Collection Systems - Household waste removed from the home
Commercial Waste Collection - Commercial waste removed primarily using dumpsters
Recyclable Material Collection - Collection of recyclable materials separated at the source of generation

Equipment

Both Vehicles and Containers are required
Average life of vehicles: 5-7 yrs
Residential collection vehicles - Packer trucks
- most have internal compactors
- Rear loaders - larger hopper not as necessary with the elimination of larger, bulky items
- Side loaders - 2 person crew (driver and loader)
- Mechanically loaded
- Front Loader, residential waste place in bin then cycled (Cal and western states)
Commercial waste collection vehicle
- Front Loader
- Hoist truck; small operation, few pickup locations, bulky items
- Tilt frame - large containers, widely used
- Trash trailers - heavy rubbish (C/D)
Recycling - compartmentalized truck

Automated Collection

¨ Usually only one driver required works best:

o without on-street parking, low hanging wires, narrow streets

· Where commitment to preventative maintenance

· Where commitment to educating public

· 60-90 gal containers

Collection Options

City-Run Collection

More control over collection
City owns and operates all equipment
City manages personnel
Funded from property tax, user fees, or utility bill
Advantages
Disadvantages
1. Municipalities tend to be less efficient than private companies
2. Capital expenditures can be difficult
3. May require passage of bond
4. Tendency to minimize short-term spending without considering long-term implications
Advantages

Non-profit
Centralized operation
City maintains complete control over waste

Private Collection

· City gives contract to firm(s) as a set fee based on bidding process, users are billed directly

Non-Exclusive Franchises

Multiple contractors competing for service in community

Exclusive Franchises

One contractor is responsible for a given area

Advantages

No capital expenditure for city
Long-term lower costs

Impose order on collection (exclusive franchise)
Regular pickup schedules (exclusive franchise)
Trash cans/trucks on street one or two days per week (exclusive franchise)
Lower costs due to improved routing and technology (exclusive franchise)

Disadvantages

Difficult to compete with large haulers
Leads to domination by a few haulers (exclusive franchise)
Citizens provide a profit to waste hauler
City can become overly dependent
Requires oversight by city

Problems and Concerns

Labor

Labor intensive
Labor unskilled
High turn-over rates
Few prospects for mechanical replacement of manual labor
Injuries and poor working conditions
Limited career opportunities

Customer Service

Frequency of service
Container and storage issues particularly for commercial and industrial
Location of pickup
Special wastes

Management and Financing Issues

Low priority
Resistance to change and new technologies
Lack of quality management
Inflation
Changing with new regulations

Technological Issues

Collection of multiple streams (recyclables, yard waste, special wastes)
Single stream vs. commingled recyclables

¨ curbside collection costs are $15/ton less for single stream

¨ sorting costs at MRFs are $10/ton more for single-stream

¨ paper quality lower for single stream

Yard waste containers - bagged material must be debagged prior to composting
Automated collection (still requires an operator)
Development of efficient routes
Vehicle weight restrictions
Vehicle turning radius and clearance

Frequency of Collection

Collection frequency has been declining since the 1950s. By the 1970s, once per week (1/wk) collection was common in half of the U.S. This trend continued into the 1980s but at a reduced rate. The south still uses twice a week collection (2/wk) almost exclusively.

Reasons for declining collection frequency include;

Proportion of putrescible waste declined (food grinders)
Better design of collection vehicles controls odors and flies
Service costs increased
Time between collection and disposal decreased
Better management

Advantages and Disadvantages of Different Collection Frequencies

Alternative	Potential Advantages	Potential Disadvantages	Favoring Conditions
Once per week or less	Less expensive, Requires less fuel	Improperly stored waste can create odor and vector problems	Cold to moderate climate
Twice per week	Reduces litter, Reduces storage requirements	More expensive, Requires more fuel	Warm climate
More than twice per week	Reduces litter, Reduces storage requirements	More expensive, Requires more fuel	Dense population

Factors Affecting Decisions and Calculations

Fixed Factors

Climate
Topography
Layout - container access (alley, curbside, rear of house)
Available transportation systems, traffic, roads (Venice uses boats)
Types of wastes collected
Population density

Variable Factors

Storage techniques employed
Recycling
Collection frequency
Crew size
Equipment

Analysis

1. Analysis of collection time

Y = a + b + c(d) + e + f + g

Where:

    Y    =     total collection time
    a     =     garage to route time
    b     =     actual time collecting waste
    c     =     number of trips to disposal site
    d     =     time to drive fully loaded truck to disposal facility, unload and return to collection area
    e     =     time to drive to garage at the end of the trip
    f     =     official breaks, including bathroom visits
    g     =     other lost time such as traffic jams, breakdowns

f + g = off route time, usually a fraction of Y

a, d, and e are a function of distance and speed
b is a function of the number of customers, time per customer, number of loads (full or partial)
c is a function of the capacity of the vehicle and its compaction ratio

2. Analysis of number of vehicles required

N = SF/XW

Where:

    N    =     number of vehicles required
    S     =     total number of customers served per week
    F     =     collection frequency
    X    =      number of customers truck can serve per day
   W    =      number of work days per week