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«Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection Guide to Recovering and Composting Organics in ...»

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Mixing can be accomplished by using: front-end loaders, manure spreaders or other farm equipment, batch or continuous mixers, and windrow turners. Regardless of the method chosen, the objective is to obtain as thorough a mix as possible to help hasten the onset of the active composting phase.

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b. Pile Formation The objective here is to create a pile large enough to sustain the “self-heating” process that accompanies active, thermophilic (requiring high temperature) composting. As a general rule, piles should be constructed at least five to six feet high by eight to 15 feet in diameter. In areas experiencing long winter seasons, pile dimensions may need to be increased to 10 feet high by 15 to 18 feet in diameter. The size and shape of the compost pile will ultimately be determined by the type of compost system that you choose and the volume of material you will be handling in a given season. In addition to adequate mass, the pile must also contain enough porosity (air spaces) to allow natural movement of air throughout the pile.

Creating piles that are too high (in excess of 10 feet) risks compression of the inner core contents due to the excessive weight of the overlying materials.

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4. Turning Turning is the physical process by which compost pile ingredients are blended and re-mixed throughout the active compost phase to help sustain thermophilic temperatures. During the turning process, compacted, settled materials are “fluffed-up”, creating air spaces. The act of turning accomplishes several things at once, including: re-mixing of pile ingredients, further physical breakdown of resistant ingredients, and redistribution of air spaces within the pile to help promote passive air flow. In addition, the turning process can be used as a moisture management tool. Piles that are too wet can be turned more often to facilitate drying, whereas piles that are too dry may be turned immediately following precipitation events to help capture and retain moisture. In addition, flattening the top of a pile prior to an anticipated rain event increases the amount of surface area available to absorb moisture. The frequency of turning depends upon the individual needs of each compost pile.

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5. Curing Once the compost mixture has completed the active compost phase, it must undergo a sustained period of curing. Curing is an important, and often forgotten, phase of the compost process. During curing, microorganisms continue the process of organic matter degradation (concentrating on organic acids, large particles, resistant compounds and other particles remaining after the active compost phase), but at a much slower, limited rate. Oxygen consumption, heat generation, carbon dioxide and water vapor evolution are all decreased as the material “matures”.

Curing is also essential in readying your product for market. Prolonged curing can make up for compost process shortcomings while also preventing the inadvertent distribution of an immature product. An immature compost product can potentially damage plant root systems due to the presence of volatile organic acids, high C:N ratios, high salt contents, or simply by competing with soil microbes or plant roots for available oxygen reserves.

When you have a reasonably mature product, you may wish to begin immediate distribution. Some facilities opt to screen the finished compost as a final processing step.

Screening improves product quality by removing contaminants and other large, uncomposted particles from the finished product. Screening provides a uniform product that is aesthetically pleasing and therefore, has increased value. The costs involved, including capital investment and extra labor, often deter facility managers from choosing this option. In fact, if you take the time to properly inspect the feedstocks, removing contaminants prior to mixing, the screening step will often not be necessary. Regardless, whether to screen or not is an individual decision dictated by the needs of your community and consumers of the compost product.

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VI. Trouble Shooting No matter how well a facility may be operated, there are invariably going to be nuisance problems from time to time. Nuisance problems are the number one complaint about compost facilities. Engineering and technology to correct these problems can often be expensive and ineffectual. The key to remember is that these are “people problems” and that prolonged nuisance conditions can lead to facility shutdown. Complaints should be met with an immediate response, including an explanation of the cause, if known. Good siting can help avoid potential nuisances by ensuring that you have adequate buffers to neighboring residences. Remember, many people “smell” with their eyes. Valleys and gullies should be avoided whenever possible, as they can carry nuisance odors to neighboring residences. Access roads should be located away from residences, maximizing the use of existing visual screens (tree buffers). However, there is no substitute for proper site management.

Most problems are often interrelated and as a result, addressing one usually solves the others.

The key to overcoming nuisance problems is to identify the root cause and correcting it.

The key to remember is that most compost problems can be avoided simply by optimizing the compost recipe (creating a homogeneous compost mixture that has a: moisture content of 40-60%; pH of 6.5-7.5; Carbon:Nitrogen ratio of between 20:1 to 30:1; and, has adequate porosity or “air spaces” within the piles) at the beginning.

The following section describes the most common nuisance problems associated with compost facilities and methods that have been developed to correct them. A condensed Trouble Shooting table immediately follows this section.

Odors: Odors signify a breakdown in the compost process. Left uncorrected, odors can drift off site impacting neighboring residences. Odor issues can be addressed by paying strict attention to process control. Incoming loads of seafood residuals should be immediately mixed with carbon amendment as soon as they are received. This is the first chance to control odors. If this is not possible, materials should be received in waterproof, airtight containers until they can be processed. Initial compost recipes should be thoroughly mixed, and the following parameters should be optimized: C:N (25:1 to 30:1), porosity (adequate air space distribution) and % moisture (45% to 60%). Finally, compost piles may also be covered with a 10 to 15 centimeter layer of sawdust, peat or finished compost to act as an odor scrubber.

Vectors: Vectors are organisms capable of transmitting diseases to humans. These organisms include birds (such as sea gulls and crows), mammals (rats and other rodents), and flies.

They are attracted to smelly, decaying materials, typically released from food scraps and other residuals that have not been properly mixed into compost piles. Vectors can be discouraged by maintaining a neat and clean operation. Grinding seafood residuals also allows for better compatibility with amendments during mixing, making the organics less

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odorous and therefore less attractive. In addition, thoroughly cleaning any on-site emptied storage vessels also reduces attractiveness to vectors.

Leachate: Leachate (typically a dark, brown liquid that is released from the composting process/excess moisture) results from poor moisture management during initial recipe formation and/or from prolonged exposure of compost windrows to heavy precipitation.

As mentioned above, initial compost recipes should have a moisture content of 40 to 60%.

Because leachate contains concentrated nutrients, it poses a significant threat to groundwater. In addition, if the piles are losing nutrients than your finished compost will be poorer in quality. There are several approaches to leachate management. The first is to prevent it. Leachate can be avoided by achieving proper mix ratios at the onset of composting.

Additionally, composting under a roofed structure or by using water resistant covering materials can help minimize the effects of precipitation on leachate generation. Many facilities try to capture the leachate by amending it with sawdust or other suitable materials, and then re-incorporate it back into the compost piles. Other facilities collect the leachate into a storage tank and then reuse it on the piles when moisture adjustments are necessary. Finally, leachate may be discharged onto a level vegetated surface for treatment. The key to leachate control is to manage moisture in the initial recipe development.

Dust, Noise and Traffic: All of these problems are often interrelated. Dust is created as a result of many compost facility operations including: materials off-loading, mixing, compost turning, screening and traffic. Dust conditions can also be exacerbated by prevailing winds, carrying particles onto neighboring properties. On site, dust can be an irritant to facility workers affecting the eyes and respiratory tract. Noise from compost equipment such as front-end loaders, grinders, mixers, transport trucks and compost turners can annoy neighbors directly abutting your facility. Increased traffic results in noise, dust, excessive speeds and bottlenecks. These issues can be addressed by developing daily operating hours, monitoring equipment noise, setting speed limits on access roads and soliciting feedback from your neighbors. In addition, dust conditions can be minimized by moistening dry compost piles and enclosing screening, mixing and turning operations.

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A. Composting in Maine Operating a compost facility in Maine offers many challenges to the beginning facility manager. Seasonal fluctuations in weather conditions, as well as seasonal availability of feedstocks, require preplanning and site preparedness. In the spring, heavy rains can saturate piles, halting compost activity, while rendering access roads impassable. Likewise, sudden winter storms can paralyze a facility by freezing compost piles and halting compost activities. The key is to develop and stick with a successful operating plan that accounts for these weather factors.

B. Winter Composting

Maine winters are notorious for being long and cold. Accumulations of snow and ice, coupled with extended periods of subzero temperatures, can spell disaster for outdoor (exposed) facilities if caught unprepared. Excessive snow must be removed and access ways kept open to allow continued facility operations. Cold temperatures slow the compost

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process by increasing the amount of heat lost by the compost pile. As this continues, pile microorganisms slow down their metabolic activity, further exaggerating the heat loss, which may result in complete halting of compost activity.

Prior to the onset of colder weather, composting piles may be combined to increase mass (to retain heat) and prevent freeze-ups. As a general rule, finished piles should be at least five feet high by 10 feet wide to assure enough mass to sustain thermophilic temperatures throughout the winter season. Piles (windrows) may also be covered with a commercially available pile cover. The covers, manufactured from a wide variety of materials, help insulate compost piles by preventing heat loss and cold infiltration. In addition, the covers shed water further protecting the pile’s surface from freezing. Even if the piles do freeze, it is important to remember that this is only a temporary condition and that the compost process will take off again once the piles thaw.

Spring composting provides additional challenges to facility operators. Periods of heavy rains and slow ground thawing may result in pad rutting and site accessibility issues. This problem can be avoided by designing and constructing an impervious composting surface as well as planning for durable year-round access during the site selection and development phase.


Many composting feedstocks are available on a seasonal basis. Leaves, for example, are collected primarily in the fall and to a lesser degree during spring clean-up. They must be composted in large quantities. Facilities must develop contingency plans to make allowances for this sudden influx. Seasonal feedstocks will require additional storage as well as adequate space for their immediate processing. Some facilities may wish to compost on a “seasonal basis”, operating only when the feedstocks are available. This method works well for small communities who save a portion of space at the local transfer station to handle incoming leaves in the fall.

Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection VIII. Compost Health and Safety Issues Prior to beginning composting at any facility, it is important to take a step back and review the process for any potential health and safety issues that operators and facility employees might face. This extra step will help you to avoid unnecessary and costly injuries. The majority of potential issues revolve around the compost process itself, and the myriad of equipment used to facilitate daily operations. This Chapter will discuss the major of the Health and Safety issues associated with the compost process, including identification of the potential hazard(s) and introduction of specific steps that can be taken to avoid or eliminate hazards.

When attempting to identify potential hazards, the first step is to conduct an “audit” of the process. This specifically means sitting down and critically reviewing how the compost materials (feedstocks) flow through the facility, from initial receipt to completion of the composting process. Materials handling at each individual step of the process should be considered.

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