«Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection Guide to Recovering and Composting Organics in ...»
4. Produce a Useful and Desirable Commodity Because composting turns discarded, organic materials and residues into a valuable end product, citizens, local businesses and public works departments can be both the suppliers of additional carbon and nitrogen feed stocks, and the end users of the compost.
B. Why now?
1. Composting has proven a track record throughout the State As stated previously, municipalities and businesses have been accepting lawn clippings and similar organics for composting for more than two decades. Some of these operations also accept small amounts of food residuals. Due to increased interest in capturing food residuals for composting and for use in anaerobic digesters, there are increasing opportunities for food scrap generators to divert their organics from landfills and waste to energy facilities to composting or anaerobic digester facilities.
2. Current Regulations Encourage Composting Efforts In February 2010, the MEDEP published the new Composting Regulations, Chapter 410 (see Section 3 of this manual for the complete rule). This revised rule provides a clear and consistent framework for environmentally sound compost operations.
3. Technical Assistance and Educational Outreach Opportunities In addition to knowledgeable staff at the MEDEP, Maine is home to two nationally known resources on composting: the Compost Team and the Compost School. Both programs are cooperative efforts by the MEDEP, Department of Agriculture, Conservation & Forestry, and the University of Maine Cooperative Extension.
Another source of assistance is available through the Northeast Recycling Council’s website; www.NERC.org. Through their on-line blog, numerous discussions on organics recycling are posted. One post that relates directly to this document may be found at http://www.nerc.org/news-and-updates/blog/nerc-blog/2013/07/30/opportunitiesand-action-in-commercial-organics-recycling. This blog post provides a thorough summary overview of separating and recovering food scraps from generators, and possible scenarios for planning and implementing food scrap programs, including discussion on transportation and facility options.
Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection Additionally, MEDEP staff can direct interested individuals to other sources of information as well. The Department has just developed a guide to specifically address food separation and composting within a school: ‘10 Steps to Starting a Successful School Composting Operation’.
For a copy of this guide, please contact Mark King at firstname.lastname@example.org III. The Composting Process Composting is a biological process in which microorganisms consume organic materials (carbon and nitrogen compounds) and convert them into a nutrient-rich, soil amendment material, commonly referred to humus. All of the composting processes presented in this guide focus on aerobic activity (with oxygen) of the microorganisms, which is when the activity of the microorganisms takes place in the presence of oxygen, and where the byproducts are water vapor and carbon dioxide (CO2). Examples would be someone’s backyard compost pile of leaves, grass clippings and food scraps, where the pile is flipped on a regular basis. Composting can also without oxygen (anaerobic), although the microbes perform poorly and the by-products may be odorous volatile organic acids which may create “nuisance" conditions.
In addition to oxygen, microorganisms also require suitable amounts of carbon, nitrogen, and moisture, to help them thrive and multiply within the compost pile. The moisture serves as the medium in which the microorganisms live; the carbon provides the energy/food source to fuel them; and the nitrogen provides the building blocks for their reproduction, which leads to further composting activity. The composting process begins when the appropriate ratios of materials (feedstocks) have been mixed together to form a “recipe”. The physical process of mixing the feedstocks usually provides enough oxygen to initiate the composting process.
The first six to eight weeks of the compost process are referred to as the “active composting phase.” During this time, microorganisms consume a great deal of oxygen as they feed on the available organic matter. At the same time, they are producing heat, water vapor, and carbon dioxide as they consume and reduce the original volume and mass of the raw ingredients and begin the process of converting the feedstocks to a more stable material, humus.
After the initial active composting period, the pile enters a “curing phase” where the microorganisms still feed, but at a slower pace, giving off lower amounts of heat, water vapor, and carbon dioxide. Left undisturbed, the microorganisms will continue to feed until all the organic matter has been consumed. The final product is a nutrient rich soil amendment that provides many benefits including: increased organic matter, enhanced soil structure, drainage and porosity, and water holding capacity. Because of these qualities, compost is a valuable end product for the local home gardener and landscape companies.
Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection A. Four common composting systems used in Maine Over the years, many composting systems have been developed and employed in Maine to facilitate the composting process. Today, though, there are four fundamental composting systems in use: the static pile, the aerated static pile, the turned windrow and the in - vessel system.
1. Static Pile The static pile method involves mixing the compost ingredients together and constructing a pile from the blended material. Subsequent turnings may not be required but are encouraged.
The least labor/equipment intensive method.
The preferred method for composting leaves.
The only equipment needed is a tractor with a bucket or a front end loader (or a very strong back!) The pile may be turned up to four times a year but will usually compost without any further management.
The composting usually happens very slowly due to the steady reduction in the amount of oxygen available throughout the pile.
When this method is used with materials that are wetter and/or contain more nitrogen, such as food scraps, a lack of sufficient available oxygen may cause the process to go anaerobic and unpleasant odors may result.
Sandy River Recycling Association (Farmington)-Static Pile (Photo by Mark King)
2. Aerated Static Pile This system involves building a static pile on top of an aeration system, either passive (usually pipes with holes drilled in along their length) or forced air, and then leaving the material without subsequent turning until the active phase of the compost process is completed. However, during this phase, air is passively drawn down through or forced upwards through the pile with fans or blowers attached to the pipes.
This ‘low-tech’ approach requires very little capital investment or accessory equipment, and as a result, has been widely used for manure and municipal sewage residual composting efforts.
3. Turned Windrow System This is the preferred method for most on-farm and seafood composting activities. It would work equally well for municipal operations with sufficient space and resources. Typically, leaves and yard trimmings are placed down in layers in long piles (windrows) and mixed using a mechanical windrow turner. Windrows are then turned as needed with the same windrow turner. A front end loader can be substituted to mix and turn the windrows though care must be taken to achieve a good level of mixing. A front end loader will require more time than a windrow turner.
This method requires more intensive management and more space (for equipment maneuvering) than the static pile/ aerated pile methods.
Pile temperature must be carefully monitored so that the row will be turned at the appropriate time to ensure successful composting.
Windrow turning machines can be costly investments.
4. In-Vessel System As the name denotes, in-vessel composting occurs within a closed system. Usually this means within a building or a container. All of the receiving, mixing and composting activities are enclosed, and exhaust gases are collected and processed through a filter. Any leachate generated during composting is collected and recirculated back into the process. Most in-vessel systems combine forced air and a form of mechanical mixing or agitation.
The immediate benefit of in-vessel systems is the rapid production of a well decomposed product without any concern for odors or leachate generation.
B. Challenges to Managing Organic Residuals The process of siting, developing and managing a compost facility can be challenging.
Organic residual generators and compost facility operators have different needs and requirements that must be considered prior to setting up a storage and transportation system in order to utilize a compost site or anaerobic digester. Additionally, many generators may have little or no on-site capacity for long-term storage of food scraps.
This creates an immediate problem, as organic residuals by nature tend to be highly putrescible and odorous due to a low carbon to nitrogen ratio (15:1) and low solids content (10% to 30%). As a result, residuals tend to decompose quickly, creating odor and releasing liquids, necessitating the need for regular removal off-site.
Ideally, the compost site should be relatively close to the residual generating facility, as trucking these residuals long distances can be cost prohibitive. Additionally, due to sales variations and other factors, generators may not be able to guarantee predictable residual volumes to compost facilities.
It is therefore critical that compost facilities and anaerobic digesters be adequately sized to handle incoming organic streams and properly designed to facilitate flow of materials throughout their process. Where food scraps can neither be composted nor utilized in an anaerobic digester by themselves, the facility must also have adequate amounts of carbon amendment on site to mix with incoming loads of organic residuals, if composting, or an active digester, into which food scraps may be added. Having sawdust, horse manures or other carbon amendments on hand are critical in creating an initial mixing to help control leachate, prevent odors and initialize the compost process.
Note: Most of Maine’s organic compost facilities charge a tipping fee to help operate and maintain their sites. This arrangement works well provided that compost facility operators accept only the volume of organic residuals that the facility can handle. It is important that facility operators do not accept more product than they can process, as this can ‘short circuits’ the compost process, leading to numerous nuisance problems including odors, leachate, and animal (vector) attraction. Once a facility begins this action, it is often difficult (but not impossible) to recover.
Compost facilities have operating hours and access control to prevent unauthorized deliveries and to properly process incoming loads. Dust, noise, and traffic can also add to nuisance problems at the site, and with neighbors. Nuisance issues are discussed more thoroughly in Section VI, “Trouble Shooting the Compost Process”.
Guide to Recovering and Composting Organics in Maine Maine Department of Environmental Protection IV. Regulations In Maine, organic composting activities are regulated under the provisions of Maine Solid Waste Regulations, 06-096, CMR 410, “Composting Facilities”. The Department provides for a Reduced Procedure For Select Compost Facilities (effective December 11, 2011) which follows below. Any compost activity that does not meet the exemptions outlined in 06-096 CMR 410, Section 1 (b), below, requires a permit which may be obtained through any MEDEP Regional offices (a complete reference list of Department Solid Waste licensing staff phone numbers and regional office locations appears at the end of this document in the Appendix).
Note: this section is designed for informational purposes only. Where applicable, you still need to contact the appropriate Department Materials Management Staff for information and complete rule reference (see Appendix for staff contact information).
Applicability. This Chapter applies to solid waste composting facilities including certain 1.
Agricultural Composting Operations. A solid waste composting facility license under the Maine Solid Waste Management Rules: General Provisions, 06-096 CMR 400 and this Chapter is required to locate, establish, construct or operate any new composting facility or to alter an existing composting facility, unless that facility is exempt from licensing under these rules. Agricultural Composting Operations which are not exempt from licensing under the provisions of section 1(B) of this Chapter are subject to the requirements of sections 2 through 4 or section 6 of this Chapter.
Facilities Not Subject to the Requirements of this Chapter. In addition to the facilities A.
listed in the 06-096 CMR 400(2), the following facilities conducting only the specified
activities listed are exempt from the requirements of this Chapter:
NOTE: See 06-096 CMR 400(1) for a full definition of residual types. Type IA residuals are leaf, vegetative and other residuals with a C:N ratio of greater than 25:1. Type IB residuals are food and other residuals with a C:N ratio of between 25:1 to 15:1. Type IC residuals are fish and other residuals with a C:N ratio of less than 15:1. C:N refers to the ratio of available carbon to nitrogen of the raw residual prior to composting. See Appendix B of
this Chapter for a list of typical C:N ratios for various residuals. The lower the initial C:N