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Introduction to Composting Mr Angus Campbell www.recycledorganics.com

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Title: Introduction to Composting Mr Angus Campbell www.recycledorganics.com


1
Introduction to Composting Mr Angus
Campbell www.recycledorganics.com
  • Recycled Organics Unit

2
Lecture Overview
  • The Composting Industry in Australia
  • What is industrial-scale composting?
  • Value of recycled organics products
  • key to reversing land degradation, ESD and waste
    management
  • Composting facility process diagram site layout
  • Types of composting technologies relative
    performance
  • Composting Facility Management - Process Control
  • Feedstock and receival
  • Preparing the mix
  • Composting phase
  • Curing and screening

5) Final product preparation 6) Quality
testing 7) Storage / bagging / sale
3
The Composting Industry in Australia
  • What is industrial-scale composting?
  • Large-scale facilities designed to process
    organic wastes (materials) into stable,
    humified and products which can be used in
    landscaping, horticulture and agriculture and a
    number of specialised applications
  • Controlled decomposition of organic materials
    with minimum impact on air, soil and water
    quality
  • Hot composting process achieve pasteurisation
    of materials (gt55C)
  • Key infrastructure to recycle organic materials
    into useful products, thereby reducing our
    dependence on landfilling
  • Facilities designed to process organic materials
    on a regional basis from municipal commercial /
    industrial and construction / demolition sources
  • Facilities may process up to 150,000 tonnes per
    annum

4
The Composting Industry in Australia
Aerial photograph of a typical outdoor windrow
composting facility in Australia - SA
5
Need for ESD
  • Better resource utilisation and conservation is
    being demanded by the community, and supported by
    State and Federal Government ESD policies
  • Management of the organic fraction of solid waste
    stream is critical - comprises up to 50 of the
    waste stream and also is largely responsible
    for the negative environmental impacts of
    landfills
  • Reprocessing of organic materials into saleable
    products avoids the impacts of these materials on
    the environment when disposed of in landfill
  • Organic materials generate methane in landfill
    (greenhouse gas, 21x CO2 equivalent), and
    contribute to high nutrient and BOD in leachate,
    which can pollute ground- and surface water
    reserves
  • Encroaching urban development, and community
    resistance to poor resource utilisation AND
    localised urban amenity impacts
  • Only 21 of organic wastes in Sydney
    Metropolitan Area are recycled.

6
Quantities of materials from GSR
Wright, T. (2000). Report of the Alternative
Waste Management Technologies and Practices
Inquiry. April 2000.
7
Value of recycled organics products
  • ? OM in soil is key to reversing land degradation
  • More than 70 of NSW is affected by one or more
    forms of land degradation from modern
    agricultural practices (1)
  • Degradation includes soil erosion, dry land
    salinity sodicity, acidification, nutrient
    decline weed invasion (2)
  • Land degradation costs NSW more than 700 million
    in lost productivity (2)
  • Recycled organics products can help stabilise
    soils, reduce susceptibility to erosion, provide
    nutrients and reduce fertiliser requirements
  • Use of organic matter for such applications is
    considered to be a high-value re-use option (cf
    waste to energy)
  • 1) NSW EPA (2000). State of the Environment
    Report. NSW EPA, Sydney.
  • 2) NSW Agriculture (1995). NSW Agriculture Annual
    Report 1994-1995. Orange, NSW.

8
Composting facility process diagram
  • Process flow diagram depends on
  • type of facility operated,
  • Type of technology used,
  • Type of materials processed
  • Range of products manufactured
  • This is typical of a large-scale, outdoor windrow
    composting facility producing a range of quality
    products
  • Majority of facilities in NSW are of this type
    (35)

9
Site layout Windrow composting facility, Wyong
Gate
Receival inspection
Mix preparation
Site office
Biosolids Incorpn
Leachate collection
Composting
Stockpiled material
10
Types of composting technologies
  • At least eight different forms of composting
    technologies are available for processing a wide
    range of organic materials.
  • Turned windrow systems have been the predominant
    form of composting in Australia, particularly for
    garden organics material.
  • Higher technology composting systems are now
    being implemented for processing materials that
    have traditionally been difficult to process in
    outdoor turned windrow systems, such as food
    organics.
  • All systems aim to control compost production by
    manipulating temperature, oxygen and moisture
    during composting. This varies from technology to
    technology.

11
Turned windrows
12
Aerated static pile
13
Aerated covered windrow
14
Rotating drums
15
Agitated bed or channel
16
In-vessel (horizontal configuration)
17
In-vessel (vertical configuration)
18
Composting technology relative performance
19
Composting Facility Mgmt Process Control
Clean, uncontaminated garden organics from a
municipal collection to be composted in windrows
  • Feedstock selection
  • Feedstock quality is of paramount importance to
    composting because poor quality feedstock
    produces poor quality composts.
  • Chemical and physical characteristics such as CN
    ratio, moisture content and porosity are also
    important since they determine whether a
    feedstock can be safely composted by a given
    composting system at a specific site.
  • Materials such as garden organics, wood chips,
    bark, food organics, manure, biosoilds, grease
    trap waste, animal mortalities are often
    composted.

Poor source separation can lead to high
contamination levels (e.g. plastic) and poor
product quality
20
Composting Facility Mgmt Process Control
Materials dropped off must be weighed and
documentation prepared to track batch
  • Receival
  • At the point of receival on site, all incoming
    raw feedstock material must be verified, weighed
    and documented, preferably into a computer
    database at the main gate.
  • Every raw material load must be inspected on
    arrival for contaminants such as glass, plastics
    and metals.
  • Depending on putrescibility of material received,
    material may be stockpiled (e.g. woody garden
    organics) or processed immediately (e.g. food
    organics)

Inspection is important, facilities may reject
batches with high physical contam-ination or
charge increased gate fee
21
Composting Facility Mgmt Process Control
Size reduction of woody garden organics prior to
composting
  • Preparing the mix
  • Careful feedstock preparation is crucial to
    successful composting in all types of composting
    systems
  • Matching the type of feedstocks that are
    processed to an appropriate composting technology
    is a critical step in the planning process for
    new facilities
  • Preparing feedstock for thermophilic composting
    involves size reduction (i.e. grinding or
    chipping) achieving the optimum carbon to
    nitrogen ratio (CN ratio) achieving the optimum
    moisture content and determining the best
    possible mix of feedstock.

Mixing of materials to achieve an optimum
composting mix before placement into windrows
22
Composting Facility Mgmt Process Control
Turning of a biosolids windrow with a Scarab
windrow turner
  • Composting phase
  • Composting process management varies with type of
    composting technology
  • For outdoor turned windrows, key process
    management steps are
  • Maintenance of thermophilic (55-60C) conditions
    to ensure rapid decomposition
  • Turning to aerate mass, improve oxygen levels,
    alleviate compaction and avoid odour formation
  • Addition of water to ensure optimum moisture
    content for microbial decomposition, and to avoid
    dust and aerosol production

Checking of oxygen levels with a Galvanic cell
oxygen meter
23
Composting Facility Mgmt Process Control
  • Curing
  • A period of curing of between 3 and 6 weeks may
    be required for a stable and mature product
    suitable for unrestricted application
  • Immature composts can be toxic to plants (if
    inappropriately / over applied)
  • Oxygen depletion metabolites such as organic
    acids root damage ammonia release (high N
    materials) N drawdown (low N materials)
  • Curing should be performed in a separate
    functional area of the composting facility
  • The site should be well-drained to prevent excess
    water accumulating at the base of piles after
    rainfall (if not under cover)

Curing of compost in an open-sided building
based on a concrete pad
24
Composting Facility Mgmt Process Control
  • Screening
  • Screening separates compost particles of
    different size and/or shapes.
  • In a composting operation, screening serves one
    or more of the following purposes
  • removes a physical contaminants from the finished
    compost including rocks, metal, glass, plastic
    etc.
  • recovers bulking agent from the compost for
    re-use and
  • Separates to meet required particle size
    specifications for a range of different products
    (eg. mulch, soil conditioner, top dressing,
    potting mix)

Photograph of a mobile screening plant. This
plant is capable of separating a range of
particle size fractions from cured compost
25
Composting Facility Mgmt Process Control
  • Final product preparation
  • After screening, the base compost product can be
    blended with a range of additives to form a range
    of value-added products e.g. engineered soils,
    coloured mulches, potting mixes, customised
    products etc.
  • Additives may include fertiliser wetting
    agents sand gravel vermiculite perlite ash
    rock dust natural soil dolomite lime gypsum
    etc.
  • Compost blends must have predictable and uniform
    characteristics to meet market demands

Photograph of a compost screening and batch
mixing plant used to manufacture an engineered
soil product
26
Composting Facility Mgmt Process Control
  • Quality testing
  • In-process testing and final product testing are
    used are critical to reduce the amount of
    non-conforming or defective product produced, and
    can guarantee its products to its customers with
    confidence
  • An inspection and testing plan is often used to
    test product at key critical control points
    during the manufacturing process
  • Conformance to a relevant Australian Standard
    (e.g. AS 4454, AS 3743, AS 4419), or to a
    performance based industry specification may be
    required by some customers

Composting facilities often have basic on-site
testing for characterising product quality. Very
few have laboratories with equipment such as
ICPs for nutrient and metal analysis, most use
commercial laboratories.
27
Composting Facility Mgmt Process Control
  • Storage / bagging / sale
  • Storage is the last step in the compost
    manufacturing process.
  • Final products should be stored in a separate
    functional area of the composting facility.
  • The conditions of storage should be adequate to
    prevent a degeneration in product quality
    through re-contamination of the final product
    with untreated materials dust and odour
    generation waterlogging and nutrient leaching
    re-commencement of thermophilic composting and
    risk of fire.
  • Some products bagged prior to sale

Photograph of a fully automatic bagging machine
manufactured by Hamer. This machine forms, fills
and seals bags.
28
Conclusions
  • Conversion of organic materials into quality
    composted products that can improve soils and the
    environment is a central component of the NSW
    Governments strategy to reduce waste disposal to
    landfill.
  • An understanding of the basic principles of
    composting science and process management will
    allow solid waste managers to select and
    implement appropriate composting solutions.

29
Further reading
  • Haug, R.T. (1993). The Practical Handbook of
    Compost Engineering. Lewis Publishers, Boca
    Raton, USA.
  • Recycled Organics Unit (2001). Establishing a
    Licensed Composting Facility A guide to siting,
    designing, gaining approval and a licence to
    develop and operate a composting facility in New
    South Wales. Recycled Organics Unit, internet
    publication www.recycledorganics.com
  • Recycled Organics Unit (2001). Producing Quality
    Compost Operation and management guide to
    support the consistent production of quality
    compost and products containing recycled
    organics. Recycled Organics Unit, internet
    publication www.recycledorganics.com
  • Recycled Organics Unit (2001). Composting Science
    for Industry An overview of the scientific
    principles of composting processes. Recycled
    Organics Unit, internet publication
    www.recycledorganics.com
  • NSW EPA (2002). Draft Environmental Guidelines
    for Composting and Related Organics Processing
    Facilities. http//www.epa.nsw.gov.au/publications
    /composting_draft_egs.pdf

30
Further information
Recycled Organics Unit publications available
from www.recycledorganics.com
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