AR 420-49 PDF

AR 420-49 PDF


June 16, 2020

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Documents Flashcards Grammar checker. They are intended to provide information on specific topics in areas of Facilities Engineering and Public Works. They are not intended to establish new DA policy.

The purpose of this Public Works Technical Bulletin PWTB is to transmit current information on composting technology and procedures that can be implemented at Army installations. Army facilities engineering activities. AR contains policy and criteria for the operation, maintenance, repair, and construction of facilities and systems, for efficient and economical solid nonhazardous waste management including source reduction, re-use, recycling, composting, collection, transport, storage, and treatment of solid waste.

Chapter 3 gives general guidance on all aspects of solid waste management, including composting in section i. Organic, compostable materials comprise a large fraction of the municipal solid waste stream. Capturing these for composting will reduce the volume of waste that an installation would otherwise dispose of in a landfill. Compostable materials include yard waste, food scraps, and some paper products. Appendix A gives detailed information on composting techniques and equipment applicable to large scale operations at Army installations.

Appendix B lists sources of additional information. Framework for Composting a. Planners in Federal, State, and local governments, and in the private sector consider a hierarchy of methods for this integrated solid waste management ISWM program: Source reduction prevents problems associated with disposal and is the most favorable waste management tool.

Recycling including composting diverts wastes from incinerators and landfills and provides for the reuse of resources. Incinerating waste is next in the hierarchy; it reduces volume and can recover energy. Landfilling is the least preferred waste management method. Landfills are very costly to site and maintain. The installation ISWM program may include any combination of these methods. This guide addresses composting.

Huge volumes of yard waste green wastepapers, food waste, and other organics can be composted in a simple, outdoor windrow system. Figure A1 shows what our solid waste is composed of, based on national averages. The potentially compostable fraction would be the yard trimmings Of course, many paper products such as newspaper and cardboard are actively recycled.

The food waste figures include uneaten food and food preparation wastes from residences, commercial establishments, institutional sources such as school cafeterias. It does not include waste from food processing industries.

This does not count private citizens composting in their back yards. However, some materials are difficult to handle or take longer to biodegrade such as fats, bones, and eggshells. Because yard waste can comprise nearly one half of the solid waste stream, banning the landfilling of yard waste has dramatically increased the life expectancy of some States’ landfills.

States also have their own recycling or waste reduction goals. Although there is no real enforcement mechanism, the military should try to meet these goals because Army installations are a large and integral part of States’ economies.


Materials generated in MSW by weight. States with yardwaste bans Source: However, planners must consider several other issues. The siting of any type of waste management facility can spark heated citizen reactions. The situation is a bit different on a military installation, but you still want to be a good neighbor, and you certainly do not want to adversely impact soldiers in any way.

Clearly define the goals and whatever pressures are pushing you to reduce waste. What fraction is compostable? Where is it generated?

What type of collection system will most efficiently gather the highest portion of compostables? The type of waste will, in part, influence the choice of composting technology. In many cases you will have a built-in market; large troop-based installations are analogous to small cities.

You must compare your potential compost generation to the demand. Also, weigh the cost of constructing and implementing composting against landfill diversion, and the value of finished compost. Composting is a controlled biological decay process involving many species of microorganisms and invertebrate animals i.

However, humans can intervene in this natural process by manipulating the organic materials and environmental conditions to speed up the composting process. The biological and physical processes are highly interrelated.

Carbon and Nitrogen Content 1 Carbon C and nitrogen N are required nutrients for microorganisms to grow and multiply.

Ideally, the compost operator should strive for a ratio of approximately 30 parts carbon to 1 part nitrogen by dry weight. N allows for rapid and efficient degradation of organic material.

Typically, green, wet plant materials have a low C: N high Nand brown, dry materials have a high C: Table A-1 gives examples of this. Examples of high N and high C materials. In reality, the correct ratio can be difficult to achieve. Some trial and error may be necessary because obtaining the correct mixture is more of a learned skill than a precise science. Nonetheless, Section gives a sample calculation.

Aerobic Degradation 1 Microorganisms need an adequate supply of oxygen to effectively degrade organics into carbon dioxide CO2humus, and inert mineral compounds. This is called aerobic biodegradation.


This is what occurs in landfills and wastewater sludge digesters. The result is a smelly mess. Air must periodically be introduced into the pile 4220-49 a variety of ways. In backyard composting, the pile is simply turned with a shovel or pitchfork.

AR 420-49 Utility Services

Moisture Content 1 Water is another essential element for successful composting. Water dissolves the organic and inorganic nutrients in the pile making them available to soil organisms for metabolic processes.

Ideally, the moisture content of the compost pile should be between 40 and 60 percent by weight. Too wet a pile will bring about anaerobic conditions, while a lack of moisture will slow or stop 420–49.

Particle Size 1 The surface area of organic materials exposed to soil organisms also determines the rate of composting.

The more finely ground a material, the 420-449 the surface area per unit weight. To increase the rate of decomposition, large pieces and hard materials should be 4204-9, shredded, chipped, or otherwise reduced in size. This is especially important for woody materials, large garden plants, and some food scraps e. Small particle size does increase the decomposition rate.


However, it also reduces the porosity, or air void space, of the pile. Low porosity restricts the flow of oxygen into and throughout zr pile, causing oxygen depletion and anaerobic conditions.

A mix of leaves and grass should be augmented with a bulky material e.

In fact, wood chips are often referred to as a bulking agent, especially in large industrial composting facilities. The temperature is measured with a long stemmed thermometer figure A-3at a depth of at least 18 in. However, of these, temperature is the most important for monitoring.

If the temperature rises above the plateau, or begins to decrease, then it is time to turn the windrow to introduce more oxygen. The act of turning will dramatically lower the interior temperature, but it will rise again to the plateau. If, after adequate time and several turnings, the temperature does not increase after a turn, this is a good indication that the windrow has finished composting. Table A-2 gives a summary of the optimal composting parameters discussed in this section.

Summary of optimal composting conditions. Nonetheless, a good compost mix can be planned and modeled mathematically. This can be done on paper, with a spreadsheet, or with an automated computer program. Figures A-4 and A-5 show a spreadsheet model used to calculate the correct mix between five different materials. Figure A-3 shows a good model with formulas.

Army Regulation 420 Series

In the spreadsheet shown in Figure 3, the user inputs the information in the light gray shaded cells: Percent moisture and bulk density are best determined through field measurements. Note that this spreadsheet works equally well for English or metric units. Just be consistent throughout in your choice of units for volume and weight mass. N and moisture content for the mixture fall into the acceptable range. The selection of the correct method depends on the type of material to compost, the amount of land area available, and the available budget.

This document focuses on windrow composting of typical yard wastes, such as grass, leaves, wood, etc. However, each technique presented in this section is described for its applicability and for the pros and cons involved in its use. Home or Backyard Composting i Backyard composting is the most practical and cost-effective method for managing yard wastes and some food wastes from single family housing areas. It eliminates the need for specialized collection systems vehicles and centralized composting facilities permitting.

This type of program is limited only by the motivation of the residents and resourcefulness of the program administrators.