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Composting of the organic fraction of municipal solid waste is receiving increasing interest in the province. Presently there are some composting operations in the province which are handling a variety of materials including leaves, fish waste, sewage sludge and animal manures. Typically these projects are evaluated on a case by case basis by the Department of Environment in terms of environmental approval. However, as composting efforts increase in terms of both scale and number it is becoming necessary to provide those involved in composting operations with some guidance with regard to the composting process and environmental protection.

The aim of these guidelines is to provide some basic information on the composting process as well as to offer guidelines relating to the siting and operation of composting facilities in the province. These guidelines will help ensure that compost can be produced without adversely affecting human and animal health, food production and the natural environment.

1. To allow for the evaluation of composting operations while ensuring that the environment is protected.

2. To bring all composting operations, whether new or existing, into conformity with the provisions and recommendations of these Guidelines so that environmentally undesirable practices will be avoided.

3. To assist individuals involved in composting operations to comply with the conditions and recommendations of these Guidelines by avoiding unacceptable environmental conditions which could lead to legal disputes concerning pollution.

Essentially there are three basic steps to composting. The raw material is prepared, the composting process takes place and then the final product is graded and prepared for sale. There are four basic kinds of process technologies: turned windrow; static pile (forced aeration); in-vessel; and a hybrid version which is a combination of the above systems.

The difference between the systems is the way aeration of the material is accomplished. There are various methods of aeration including agitation, injection and a combination of the two.

Agitation can be accomplished by turning, tumbling or stirring. Air injection, or forced aeration, is accomplished by forcing or drawing air through the composting mass. Injection often is used in combination with agitation. Individual in-vessel compost systems may depend entirely on agitation or injection, or may use them in combination.

Of the composting technologies, the turned windrow and forced aeration methods are usually classified as "open" systems as typically they are not contained in a structure. This does not exclude enclosing the operation in a shelter or building. Both of these systems use elongated piles, referred to as windrows, to manage the composting material.

In-vessel composting systems can be categorized as an "enclosed" system as the compost is mixed mechanically in a structure. Many of these systems use a vessel to accomplish the mechanical mixing of the compost and the other stages occur in windrows. Such combinations can be referred to as hybrid systems.

In order to better understand the description of the operating and control parameters, a brief explanation of the composting process is included here. There are two stages to the biological activity associated with composting. The first stage is the active stage in which there is a high rate of biological activity taking place. The temperature of the compost mass increases to 60 degrees Celsius. During this time the readily biodegradable material is decomposed to less readily degradable components. As this occurs the temperature of the mass drops because of a slowing of microbial activity. This second stage is known as curing or the maturation stage and ends when the material reaches the required degree of stability. Hence, an important consideration in the evaluation of a compost system is the fact that the compost process is finished only upon completion of the curing stage.

The compost process is complete when the original organic material cannot be identified and the compost has a fresh earthy smell. At this point, the mass has been stabilized to a point where it can be stored without causing nuisances and can be used without inhibiting plant growth. The curing interval is particularly important because it must be long enough for the composting material to have reached the final level of stability.

The length of time required to complete the composting process will depend upon the nature of the waste and the system employed. For example, yard and park debris, including grass clippings and leaves with the proper balance between the nutrients of carbon and nitrogen (C/N), composting can be accomplished in four to eight weeks. Leaves without the proper C/N ratio can take two to three years to compost. Municipal solid waste, with or without sewage sludge, can take eight to 24 weeks. Sewage sludge alone (with suitable bulking) can take six to eight weeks. Animal manure and assorted food processing wastes (that have been appropriately bulked) can take six to eighteen weeks to produce compost.

Unless there is an obvious problem no effort is required to ensure the adequate temperature is achieved. The pile reaches the highest temperature, between 55 to 60 degrees Celsius, when the degree of microbial activity is greatest. The temperature of the pile will rise quickly as this is the most active stage of microbial activity, which is referred to as the thermophilic stage.

Eventually the microbial activity decreases and the temperature cools. This return to ambient temperature is referred to as the mesophyllic stage.

Typically the highest temperature is achieved in the first 10 days of the composting process and then gradually returns to the initial temperature over a period of six to eight weeks depending upon the nature of the material.

If the temperature of the pile is too high, microbial activity will be impaired and efforts may have to be taken to lower the temperature depending upon the type of system being used. The usual approach is to increase the rate and extent of aeration.

If the temperature rises too slowly or there is no temperature rise then not enough microbial activity is taking place. The attainment and maintenance of thermophilic temperatures for a time period is required for weed and pathogen control. If the temperature rise is inadequate the reason may be an operational or other problem.

Ideally the moisture content should be between 45 and 55 percent. If the moisture content of the mass is eight percent or lower, microbial activity will cease.

Too much moisture prevents air from being supplied to the microbes. For this reason it is necessary to add bulking agents such as wood chips, straw, or leaves to wastes that have a high moisture rate such as cannery wastes, sewage sludge, and fresh manure.

Although composting can occur without oxygen (anaerobic systems), composting systems which use oxygen (aerobic systems) are considered more efficient, reliable and can tolerate sudden changes in environmental conditions. Aerobic systems are less likely to cause nuisance conditions such as objectionable odours.

If the composting mass is producing foul odours, then this could be an indication that there is not enough oxygen present in the pile. A slow temperature rise during the active stage of the composting process or an unexpected drop in temperature in later stages is another indication that the pile needs better mixing to provide additional oxygen to the pile. Other signs include the slowing in the breakdown of the organic matter and the absence of expected physical changes in the composting mass.

In practice the rate of aeration should be determined by experimenting with the waste to be composted. If aeration is achieved by turning then how often the turning occurs becomes the important consideration in trying to supply enough oxygen. With composting systems which used forced aeration the rate and volume of throughput air is the primary factor to be considered.

While it is possible to accelerate composting by adding pure oxygen to the input air stream it is unlikely that the benefits would out-weigh the cost of such an approach.

The organisms which create the compost, like all living things, need moisture, air and a source of nutrients. The most important nutrients to supply the microbes in a compost mass are carbon and nitrogen. Other nutrients including cobalt, manganese, magnesium and copper should also be present but in smaller amounts. Calcium can also be important to ensure that the pile can resist changes in acidity (pH). Nitrogen is probably the only nutrient which needs to be added to ensure that a suitable carbon/nitrogen ratio is achieved.

The nutrients must be present in a form that the microbes can use or digest. Some substances will be very resistant to breakdown by the composting process even under ideal conditions. These can include wood, straw and paper as well as feathers and shellfish.

Experience has shown that, with the exception of carbon and nitrogen, most organic wastes contain nutrients in the amounts and ratios required for composting. The ideal carbon/nitrogen ratio is 25 to 30 parts carbon to one part nitrogen. The composting process becomes increasingly slower as the ratio rises beyond this range. The carbon/nitrogen ratios for a number of organic materials are shown in table 1.

In theory, the smaller the particle size, the more rapid the rate of decomposition. However, below a minimum size this does not hold true as the air space provided by the particles supplies oxygen for the composting process. For material which is rigid, such as wood chips, the optimum size is from 5 to 7.5 centimetres. The maximum size for green plant material such as food wastes, fruit and lawn clippings should be no less than 5 centimetres and the maximum size can be as large as 15 centimetres.

To ensure decomposition occurs uniformly throughout the composting mass, it is important to ensure proper mixing takes place. Mixing ensures that all compost material is exposed to conditions which will destroy pathogens. For aerobic composting, it renews the oxygen supply in the spaces between particles necessary for composting to occur. Mixing also helps reduce excess moisture from the composting mass.

Usually the pH level drops to about 5 as soon as composting conditions have been established. This initial drop is soon followed by a gradual rise that continues until a level of approximately 8.5 is reached. It is unnecessary, therefore, to add lime to the process. The one possible exception may be in the composting of fruit waste in which case the initial drop may be slightly lower. Adding lime can, however, improve the physical condition of the composting mass by improving the porosity and texture of the pile.

1. Name and address of proponent.
   
   
2. Written description of composting methods, equipment employed and management of site.
   
   
3. Type and volume of waste to be composted, source of raw materials, bulking agents and leachate control methods.
   
   
4. Proponent's knowledge and experience on composting and the marketing strategy for the final product.
   
   
5. Location of the proposed composting operation indicated on a 1 :12,500 scale map or equivalent sketch indicating separation distances to the following:
   
   

   - farms - private wells - industrial areas - residential areas - right of way of local roads - right of way of arterial or collector highways

   - watercourses - commercial areas - property boundaries - watershed boundary

6. The slope of the land surrounding the proposed composting location.