Introduction to Composting Mr Angus Campbell www.recycledorganics.com

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Introduction to CompostingMr Angus
Campbellwww.recycledorganics.com

• Recycled Organics Unit

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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
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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

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The Composting Industry in Australia
Aerial photograph of a typical outdoor windrow
composting facility in Australia - SA
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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.

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Quantities of materials from GSR
Wright, T. (2000). Report of the Alternative
Waste Management Technologies and Practices
Inquiry. April 2000.
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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.

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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)

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Site layout Windrow composting facility, Wyong
Gate
Receival inspection
Mix preparation
Site office
Biosolids Incorpn
Leachate collection
Composting
Stockpiled material
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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.

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Turned windrows
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Aerated static pile
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Aerated covered windrow
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Rotating drums
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Agitated bed or channel
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In-vessel (horizontal configuration)
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In-vessel (vertical configuration)
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Composting technology relative performance
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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
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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
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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
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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
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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
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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
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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
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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.
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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.
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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.

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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

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