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1.
What is composting?
Composting is a natural biological process, carried out under controlled
conditions, which converts organic material into a stable humus-like product
called compost. During the composting process, various microorganisms,
including bacteria and fungi, break down organic material into simpler
substances. Composting is an aerobic process, meaning that the microorganisms
require oxygen to do their work.
2. What can be Composted?
Composting has the potential to manage all of the organic material in
the waste stream which cannot otherwise be recycled. Some examples of
organic material that can be com posted include food scraps, leaves and
yard wastes, agricultural crop residues, paper products, sewage sludge
and wood.
3. Can composting manage all our wastes?
Since approximately 50% of the waste stream is organic matter, composting
can play an important role in the integrated waste management plans of
any community. However, the remainder of the waste stream (such as items
made of plastic, glass, metals, ceramics and rubber) cannot be composted.
4. Is composting compatible with other
waste management systems?
Yes. Composting should be part of a comprehensive waste management system
that emphasizes source reduction, reuse, composting and recycling, and
proper disposal of any residual material. Some materials (such as paper
products) can be recycled or composted. While paper can be composted,
clean paper is generally more valuable when recycled. Soiled paper or
paper that cannot be recycled economically can be composted.
5.
What are the benefits of a successful composting program?
In addition to diverting a large proportion of the waste stream away from
disposal, an effective composting program can produce a high quality soil
amendment with a variety of end uses. Diverting organic wastes from landfill
sites helps to conserve landfill space and to reduce the production of
leachate and methane gas (both of which add to the cost of operating a
landfill).
6. Is composting new?
No. Agricultural wastes have been com posted forever. Large scale composting
of other organic wastes, including municipal sewage sludge, has been a
component of some municipal waste management programs since the 1950s.
7. What
different types of composting systems have municipalities implemented?
Municipal composting programs can include a combination of backyard, on-site
and centralized management approaches for all or a portion of a municipality's
waste stream. The. major differences between these approaches are described
below. Backyard Composting - Many councils or municipalities encourage
"Home" or "Backyard" composting, where individual
households compost at home.
On-Site Composting - The industrial, commercial and institutional sectors
can take advantage of larger scale on-site systems to manage their organic
wastes and avoid disposal costs.
Centralized Composting - Many organic waste generators will not be able
to compost all of their wastes on site and therefore rely on programs
to collect and compost their wastes at a centralized facility.
Many councils or municipalities have implemented programs to collect and
compost leaf and yard wastes in conjunction with home composting programs.
Combined programs for the collection of organics and recyclables, known
as "wet/dry" programs have been tested in several municipalities
in Canada and the US. Full-scale programs are being implemented in Canada.
8. How long does the composting process
take?
A number of factors are important in controlling the composting process
and the time that the process takes. These factors include temperature,
moisture, oxygen, particle size, the carbon-to-nitrogen ratio of the waste
and the degree of mixing or turning involved. In general, the more actively
these factors are controlled, the faster the process. The length of the
process also depends on the degree of decomposition desired in the finished
product. Typically, an immature compost can be produced in about a month,
while a mature compost may be allowed to cure for six months to a year.
9. What is the best location for a
backyard com poster?
The composter should be placed in a well drained area and where it is
convenient to use. It should be placed where it can get as much sun as
possible as the microbiological activity will be high. If the unit is
placed in the shade, the activity is reduced and the process takes longer.
10.
Can I compost in the winter?
Yes, you can compost year-round. As the temperature falls, microbial activity
decreases but it starts up again as soon as the weather warms up. To make
room for your winter organics, empty the finished compost from your unit
in the fall. You may also want to move the unit to a more accessible location
for the winter. Also, organics can be collected in a covered container
stored just outside the back door. In the spring, the collected organics
can be added to your com poster. Kitchen wastes are high in nitrogen so
you need to add lots of leaves or something rich in carbon to be sure
that you have the right carbon-to-nitrogen ratio needed for the microorganisms
to be most effective.
11. Are there many centralized composting
facilities in Canada? Or Australia?
There are about 162 centralized composting facilities in operation or
in plan across Canada. These facilities, which include a mix of publicly-
and privately owned and operated operations, processed almost 700,000
tonnes of organic waste in 1995, an increase of 154% versus 1993. Australia
has a number of large compost producers using a variety of techniques.
Many hobby farmers also contribute to the market. Compost Australia is
working with producers, the EPA and interested persons in ensuring the
Standards of compost are recognized.
12. What are the different types of centralized composting
processes?
There are three basic types of centralized composting processes or methods.
In the In-Vessel Method, the organic material is composted inside a drum,
silo, agitated bed, covered or open channel, batch container or other
structure. The process conditions are closely monitored and controlled
and the material is aerated and mechanically turned or agitated. The Aerated
Static Pile Method involves forming compostable materials into large piles,
which are aerated by drawing air through the pile or forcing air out through
the pile. The pile is not turned. In the Windrow Method, compostable material
is formed into elongated piles, known as windrows, which are turned mechanically
on a regular basis. Specific windrow turners are manufactured to maximize
the environment within the windrow and quicken the production process.
13.
Are special additives required?
In some cases, such as in the composting of grass clippings, the raw material
may be too dense to allow for the proper flow of air or may be too moist.
A common solution to this problem is to add a bulking agent, such as wood
chips, to provide structure to material and to allow for proper air flow.
The amount of bulking, agent required is usually determined based on experience.
Some facilities add commercial fertilizers to their composting process,
but this can usually be avoided by combining different waste streams together
in a specific "recipe". Inoculating the material with microbes
is not normally required, since most wastes naturally contain the microbes
needed for successful composting to occur.
14. Does composting cause odours
or attract rodents?
Any waste management facility, including a composting site, has the potential
to generate offensive odours or to attract pests. However, experience
at hundreds of composting facilities has shown that proper design and
operational procedures can prevent or control these problems. Excessive
or offensive odours are generally a sign that the composting process is
not proceeding properly, usually because of inadequate aeration or excessive
moisture. Close monitoring of these factors can usually help to minimize
odours. Facilities can employ abatement systems, such as biofilters, to
treat occasional odours. Preventing odours and ensuring that the site
is kept clean will ensure that the site does not attract rodents or other
pests.
15. Does composting pose a health
risk to workers or to those located near a facility?
Some people have expressed a concern that certain microbes present at
composting facilities and the compounds they produce, may become airborne
and endanger the health of site workers and those located downwind of
a composting facility. Studies of concentrations of fungal spores and
other airborne materials at and near composting sites show that concentrations
are higher around some composting operations, such as turning and screening,
and the levels drop to background levels within a short distance. While
airborne concentrations of fungal spores and other microbes at composting
sites are higher than background levels, studies of long time compost
site workers show no negative health effects. Wherever decaying organic
matter is present, certain microbes occur naturally. Spores of the fungus
Aspergillus fumigatus are commonly cited as a source of concern. Aspergillus
fumigatus is one of the most widely distributed microorganisms on earth
is known to exist in almost every interior and exterior environment. People
are routinely exposed to low levels (and occasionally high levels) of
Aspergillus fumigatus without consequence.
The conclusion reached by health and environmental
agencies in the US and Europe is that normal, healthy individuals suffer
no increased health risk by either working at, or living near, a compost
facility. However, some individuals may be more sensitive to microbes
at a composting facility (because of a reduced resistance resulting from
drugs or disease). These individuals should not work at composting facilities.
16. What is the cost of a composting
facility? How does composting compare to other waste management activities?
Unfortunately, there is no simple answer to this question - in part, because
of the wide variety of local circumstances that influence the cost of
waste management. An accurate estimate of the cost of a composting facility
requires detailed knowledge of project specific criteria such as location,
site conditions, waste composition, facility size and level of technology.
The cost of collecting and composting organic wastes should be evaluated
as a component of an integrated system of waste management since increased
diversion through composting will result in lower costs for collection
and disposal of garbage.
17. How much space is required?
The amount of space required for a composting operation depends greatly
on a number of factors including the quantity of waste to be handled,
the composition of the waste, the system design and operating conditions,
and the length of time that the material will be on-site. For example,
an on-site, in-vessel composter in an institutional setting can take up
a minimum of space, especially if the compost is moved elsewhere for curing.
Conversely, windrow facilities can range in size from about 1 acre to
more than 20 acres.
18.
What approvals and siting issues can I expect to encounter when planning
a centralized composting facility?
Most local governments regard composting sites to be waste management
facilities which require formal approvals or licenses. Some councils have
exempted some types of composting (such as leaf and yard waste facilities)
from the full approval process, but still require that they be properly
sited and operated. Municipal governments should also be consulted about
by-law and other siting requirements. Most jurisdictions are concerned
about issues such as the distance to neighbours, local soil conditions
and potential impacts on local water and groundwater. Proponents of composting
facilities are strongly advised to consult the provincial environmental
department early in the planning stages to discuss siting and other approval
requirements.
19.
What is the best way to collect organic wastes?
This question continues to generate considerable debate, despite growing
experience with the collection of organic wastes. Determining the "best"
method in any circumstance will require tradeoffs between the conflicting
objectives of low cost collection and low cost processing. For example,
the use of plastic bags may lower collection costs, but may increase the
cost of processing to remove unwanted plastic. Conversely, the use of
curbside collection containers makes processing easier, but requires more
capital expenditure for collection equipment.
20. What makes good quality compost?
Exactly what makes good quality compost is usually best determined by
the requirements of the end user of the material. However, there are a
number of important criteria which are normally used to judge compost
quality. Among these are maturity, organic matter content, the presence
of physical contaminants (such as glass, metal or plastic), pH, particle
size, nutrient content, moisture content and trace element content.
21. Are there regulations or standards
for compost quality?
Australian Standards - Compost produced in Canada may be subject to regulation
by the federal and the provincial governments. Several provinces have
guidelines and standards which determine the suitability of the material
for use on a regulated or unregulated basis. Agriculture and Agri-Food
Canada regulates compost offered for sale in Canada through the federal
Fertilizers Act. The Canadian Council of Ministers of the Environment
(CCME) has worked to establish national guidelines for compost quality.
In addition, the Bureau de normalisation du Quebec (BNQ), a member of
the Standards Council of Canada, has developed voluntary industry standards
for compost quality. Compost which meets this standard will be able to
bear a BNQ label as an indication of its quality.
22. What steps can be taken to ensure
that a facility produces high quality compost?
The most important step in producing a high quality compost is to control
the quality of the material entering the process. This is most often achieved
through source separation. Source-separated organics are those organic
wastes which have been separated from potential contaminants prior to
collection. Other contaminants can be removed through a pre-processing
stage or by screening the final compost. Finally, the composting process
itself can determine some characteristics of the final compost, such as
maturity and particle size.
23. Are there markets and end uses for compost?
Compost can be used in many applications depending on the quality produced
and the quality of the product. High quality compost is being used in
agriculture, horticulture, landscaping and home gardening. Medium quality
compost can be used in applications such as erosion control and roadside
landscaping. Even low quality compost can be used as a landfill cover
or in land reclamation projects.
24. Is compost a fertilizer?
Compost can contain varying amounts of nutrients such as nitrogen, phosphorus
and potassium. However, the concentrations of these nutrients in compost
are usually lower than those found in common fertilizers. Compost is more
properly described as a soil amendment or soil conditioner which returns
valuable organic material to the soil. In addition, compost does benefit
the soil be improving soil structure, aeration and water retention.
25.
How can I get more information about composting?
Contact Recycle and Composting for all your requirements.
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