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WELCOME TO THE MASTER COMPOSTER PROGRAM

The goal of the Master Composter Program is to bring together a group of mindful, enthusiastic citizens interested in a comprehensive understanding of composting who will then share the benefits of composting with their communities. The humble compost pile sits at the crossroads of several important movements focused on enhancing the quality of life and sustainability of our communities: resource conservation, waste diversion, water protection, carbon footprint reduction, organic and local food production, and community engagement. Sharing an understanding of composting as an ecologically-sound, practical, rewarding, and relatively easy practice is an excellent way to foster environmental stewardship among diverse audiences; and Master Composters are vital ambassadors for composting in our communities. While introductory workshops can begin to impart this information, the Master Composter Training Course goes two steps further. First, it offers a more complete knowledge of composting processes and options and the motivations for dedicating one’s time and resources to composting. Second, after completing the four-week course, graduates are motivated and qualified to share their knowledge with others in informal and formal settings from backyards and gardens to workshops and community outreach events. From building compost piles in community and school gardens, to teaching children about worms and conducting workshops, Master Composters work on a grassroots level to support the development of vibrant, sustainable communities. We want to welcome you to this exciting, hands-on course and thank you for your interest in a more sustainable world.

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DEFINING COMPOSTING

IT’S NOTHING NEW Composting, or the management of the natural process of decomposition, is not a new practice, and modern-day composters are in the company of agriculturalists from many cultures and eras. Perhaps the earliest recorded reference to compost appears on a set of clay tablets from the Akkadian Empire in the Mesopotamian Valley, dated at approximately 2300 BCE. The Romans and Greeks used compost, or at least knew of its value, and it is referenced in diverse texts including 10th century Arab writings, Shakespeare, and accounts from early settlers in America.

RECYCLING ORGANICS AND CONSERVING RESOURCES Over the years, the process of composting has essentially remained the same. Only the tools and systems for creating optimum conditions and minimizing problems have been refined to meet the challenges of an increased and more diverse waste stream, urbanized landscapes, and intensifying pressures on air, land, and water quality.

Although it’s commonly considered a natural recycling process, composting, as opposed to simple decomposition, requires human intervention. In short, composting is managing the decomposition process of organic matter (food scraps, yard trimmings, manure, etc.) by creating favorable conditions for microorganisms to convert these materials into a beneficial soil amendment. All organisms that were once alive will decompose in the natural environment, but composting focuses on

managing the process to support the work of decomposer organisms in accordance with human goals.

Throughout these chapters and during the course, we will explore many composting options and variations in an effort to help you balance materials, moisture, air, time and energy in a system that works for you. Regardless of the system, composting provides a new perspective in which a world formerly full of “waste” is transformed into one with an abundance of resources. As old banana peels and spent garden plants are converted into a medium that promises vigorous new growth, the composter gains a greater understanding of the cycles of decomposition and regeneration.

TWO MAIN CATEGORIES OF COMPOSTING Composters have developed myriad systems and strategies for recycling organics, and the world of composting is characterized by diversity, adaptability, innovation, and curiosity. Home-scale composting strategies can be broadly classified into two overlapping categories: traditional backyard composting and vermicomposting. Traditional backyard composting

According to the EPA, Americans throw out over 25% of the food we prepare,

equaling approximately $1 billion each year in disposal costs.

Composting allows us to maximize resource utility and availability by

rethinking our conception of ‘waste’.

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typically refers to a pile or bin where diverse materials (“browns” and “greens”) are collected and their decomposition is controlled to support the work of microorganisms. Traditional composting management strategies are focused on supporting microbe rather than worm populations, although earthworms often find their way into the bin during some part of the process. Vermicomposting uses worms and their associate organisms to break down organic matter (particularly fruit and vegetable scraps) and specifically encourages an environment in which

worms thrive. Typically, vermicomposting uses species of worms that rapidly digest fruit and vegetable scraps and move laterally so are best suited to shallow containers or surface strata. Vermicomposting will be covered in detail in Chapter 3. We will begin with a description of the ingredients and optimal conditions for traditional backyard composting in which naturally occurring micro- and macro-organisms perform their decomposer roles in outdoor piles or bins.

A BIOLOGICAL PROCESS The essence of compost management involves balancing conditions for microorganisms to convert raw organic materials into compost in the shortest period of time with minimal inconvenience to the composter. Composting can be as simple or complex as we prefer to make it. Like most activities, our return is a direct result of what we invest in time, energy, and thought. A little knowledge of composting, however, goes a long way, and we can accomplish our goals of environmental stewardship and creating an excellent soil amendment with a fairly minimal amount of effort. Before establishing your own backyard composting system, or teaching others how to do it, it’s important to ask a few questions: First, why have you decided to do it? Is it because you want to recycle organic materials and conserve resources? Is it because you are an avid gardener and want to build a foundation of healthy soil? Or is it a combination of both? Second, what type of organic materials does your household generate and how much? Other factors to consider are how much time, physical energy and funds one is willing and able to expend on composting efforts and what space is available for composting. Once you've answered these questions, you'll be well on your way to choosing the best composting method for your particular situation. In the next chapter, we will discuss factors to consider when developing a composting system to match your resources and needs.

TRADITIONAL COMPOSTING: KEY INGREDIENTS AND IDEAL CONDITIONS The headings below outline the fundamental parameters of traditional backyard composting that composters must consider and balance for successful composting. Each ingredient or factor has a range in which successful composting can take place. Effective composting systems will include the four main ingredients of carbon, nitrogen, water, and air in some combination,

This homemade multi-bin system is an example of traditional backyard

composting.

Vermicomposting is a versatile decomposition method, and is discussed further in Chapter 3.

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but composters vary greatly in how closely they adhere to the “optimal” conditions which typically are focused on thermophilic, or “heat-loving” bacteria. Although thermophilic organisms are the most efficient decomposers, they are part of a vast network of microorganisms and invertebrates that include other bacteria, actinomycetes, fungi, mites, springtails, beetles, ants, centipedes, and worms. Ideal composting conditions support a great diversity of these organisms and may fluctuate in temperature, moisture, and other factors at different points in the process, recruiting different microbial populations during each stage. Overly prescriptive or rigid composting information can discourage potential composters who have limited time to devote or who would prefer to experiment for themselves. The following guidelines are intended to promote success, learning-by-doing, and adapting the system to your goals is also an important part of the process. CARBON-TO-NITROGEN RATIO Optimum ratio: 30 parts carbon to 1 part nitrogen A carbon-to-nitrogen (C:N) ratio, or "recipe mix", of approximately 30:1 is the diet aerobic (oxygen-loving) microbes need to thrive. Although micronutrients in smaller amounts are important in their diet too, providing this ratio of carbon (their energy source) and nitrogen (necessary for their propagation and growth) is crucial to the composting process.

All organic matter contains both carbon and nitrogen, but some materials (nicknamed “browns”) are much more carbon-rich than others with C/N ratios ranging from 40-800 parts of carbon for every 1 part of nitrogen. Nitrogen-rich materials (the “greens”) are those with ratios ranging from only 5-30 parts of carbon for every 1 part of nitrogen. In general, good sources of carbon (the browns) are brittle, dry, and with no “life” left in them. These materials may have started out as green and vibrant, but over time, much of their nitrogen content has dissipated. Thus, fresh garden trimmings (“greens” with a ratio of about 30:1) left out in the open for several weeks will lose much of their nitrogen to the air, turning them into “browns” with a higher C:N ratio (perhaps more like 60:1). Examples of carbon-rich browns include: paper, dried leaves, twigs, and straw. On the other hand, nitrogen-rich materials are closer to their fresh origins and are characterized by greater moisture and typically putrify, or smell bad if left to rot in an enclosed space. Examples of materials with relatively high nitrogen content include: fruit and vegetable scraps, manure, fresh grass clippings or green garden trimmings, fresh weeds, and coffee grounds.

Controlled decomposition requires the creation of an

environment where microbial communities can thrive.

Carbon-rich cardboard can also serve as a useful “cap”

on the top of your pile.

Adding coffee grounds with filters provides a

natural nitrogen-carbon balance.

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Following are a few compostable materials and their approximate C:N ratios:

Materials high in carbon Materials high in nitrogen

Cardboard 500:1 Pine needles 500:1 Sawdust 450:1 Wood chips 200:1 Newspaper 175:1 Office Paper 150:1 Straw 80:1 Dried oak leaves 80:1 Dried maple leaves 40:1

Poultry manure 5:1 Rabbit manure 5:1 Kitchen scraps 15:1 Fresh grass clippings 20:1 Cow manure 20:1 Coffee grounds 20:1 Fresh garden trimmings 30:1 Horse manure 30:1 Urine 15:1

So, how do we achieve the ideal 30:1 ratio in our compost piles? One easy, but rough guide is to start with a mix of approximately 50% brown materials and 50% green materials by weight. The brown materials provide not only a source of carbon but also the bulk the pile needs for porosity and good aeration. The nitrogen balances the carbon to help fuel a strong microbial population. A mix of approximately half nitrogen-rich and half carbon-rich materials provides a good starting point and a convenient guideline. However, erring on the side of more brown materials is typically recommended to avoid excess moisture and odor. Experience will show that the wide range of C:N ratios within the categories of “browns” and “greens” can have a significant impact on how those materials interact in a pile. Keeping a diversity of materials can help buffer against any extremes in C:N ratios. Alternatively, you can reduce the proportion added of potent carbon or nitrogen source or try to match strong browns with strong greens. Signs that you have reached the optimal 30:1 balance include a rise in temperature (signaling increased microbial activity), materials converting into a dark and crumbly material, and the absence of any strong rotting odors.

MOISTURE CONTENT Optimum: 40-50% The aerobic, oxygen loving, organisms breaking down organics in a compost pile require water to survive. They need it for vital functions such as digestion and movement. A compost pile with adequate moisture will provide the conditions for aerobic microbes to work at their highest efficiency. How do you determine whether your pile has the proper moisture content to keep the aerobic microbes comfortable? In composting, our senses of sight, smell, and touch are some of the most valuable tools. One of the best gauges of moisture level is to dig several inches into your established pile and grab a handful of material. If the moisture content is ideal, the handful of material will feel moist like a wrung out sponge. You should be able to squeeze 1 or 2 drops of water from it. In Southern California environments, moisture content is one of the most important factors of the

Keeping a consistent moisture level in the pile is especially

important in hot, dry climates like Southern California.

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composting process to monitor. Expect to add water as you build a new pile or when adding significant amounts of dry “browns”. When adding materials to your pile or turning or mixing it, you will also want to check for the moisture level. If the pile does become too dry, do not despair. Simply adding water is enough to create the conditions for a microbial bloom. As organic materials break down, their moisture-holding capacity increases, but when you first build your pile the materials may repel water, so you may have to water your pile more frequently at first. This is especially important in the Southern California climate, where there is little rain to help keep compost piles moist. You can add water to your pile with a hose, bucket, watering can, etc. Try to incorporate water throughout the pile. If you feel you’ve added too much water and the pile is starting to smell, you can simply add more browns to help absorb excess water and turn the pile to introduce more air.

To ensure that the composting process is as water-conscious as possible, consider the following strategies for conserving water resources when composting. One effective practice is to soak the dry, carbon-rich materials in a wheelbarrow or bucket prior to adding them to the pile so the water does not simply run over them and into the ground below the pile. Another method to conserve water is to site the pile in the shade. Microbial activity, not energy from the sun, is primarily what causes compost piles to “heat up,” so retaining moisture by placing the pile away from direct sun is important for creating an optimal environment for decomposers. Lastly, covering the pile with a thick layer of “browns” (e.g., pine needles, straw, dried leaves, burlap, sheets, or blankets) will help

retain moisture in the pile. The plastic lids and sides of commercial compost bins also contribute to moisture retention. To reduce reliance on precious potable water, you may want to leave a barrel or tub outside near the compost pile to collect rainwater to use in maintaining the pile’s moisture. OXYGEN CONTENT Optimum: 5-15% To maintain the proper amount of oxygen in your pile, begin with the optimum amount of brown, bulky materials, such as dry leaves, woodchips, and straw. In addition to being a source of carbon, these materials -- referred to in composting as "bulking agents" -- give the pile porosity (small air spaces throughout the pile). You may also choose to build your pile on a base of twigs, coarse woodchips, or stones to allow air to enter through the bottom and flow through the pile out the top. This works especially well for a less active pile that is not likely to be completely turned. A piece of rebar or a commercially available aeration tool pushed into the pile in several locations can also be used to make vertical airflow channels. “Fluffing” or “ruffling” a pile with a garden fork is another easy way to aerate a pile.

Capping your pile with a durable and breathable ‘brown’ like pine needles helps seal in moisture,

and discourages pests from buried food scraps.

The amount of effort you dedicate to turning your pile is up to you! More aeration leads to faster processing of materials.

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Completely “turning” the pile is the most sure-fire way to introduce air throughout the pile. This method involves using a pitchfork or similar tool to shift all the material in the pile to an adjacent space, or footprint, next to the original pile. Materials from the top will now be on the

bottom and materials from the outside perimeter should be aimed at the center of the new pile to promote more consistent decomposition. As you turn the pile, you will have the opportunity to assess the decomposition process and moisture content

throughout the pile and can address pockets of anaerobic (smelly) activity by breaking up clumps and introducing oxygen. Turning the pile will have a drying effect, so you might need to add moisture, especially in the early phase of composting. The amount of turning or aeration a composter does is largely a matter of goals and personal preference. A pile that is never turned may be associated with a longer and less even decomposition process, but finished compost will appear, first at the bottom and internal core of the pile. Passive aeration from bulky carbons can be an effective and less-labor intensive method which works well for many composters. For those interested in quick, “hot” piles, turning may be a weekly activity for the first few weeks until the pile is allowed to rest and “cure.” PARTICLE SIZE AND SURFACE AREA The particle size of organics being composted is important since microorganisms work on the surface area of materials – the greater the surface area, the more efficiently they will decompose the materials. Sawdust and logs, for example, have similar C:N ratios, but sawdust, with a much greater surface area, will compost much more quickly than a log or a two-by-four. However, materials that are very small and moist (wet grass or fruit and vegetable pulp, for example) impede porosity and oxygen availability unless they are mixed with adequate bulking materials. Materials can be chopped at their source (e.g., in the kitchen or when mowing the lawn) or when added to the compost pile (with hedge shears, loppers, hand clippers, a spade, or even a commercial shredder/chipper). Many composters do little chopping, preferring to save their energy and allow the microbes to work over several months instead. PILE SIZE Any size between 5 gallons and large, 5ft. high windrows. An often-cited ideal for “hot” composting is a cubic yard, or approximately 3 ft. x 3 ft. x 3ft. The size of your pile will depend on the amount of material you have to compost and the space available in your yard. Piles with more material will often have greater interactions between the carbon and nitrogen sources as well as enough mass to insulate the more active core.

Chopping materials will promote faster processing. It is especially useful to

break down resistant items like thick or woody stems, whole fruits and

vegetables, and paper products.

Aerobic decomposition ensures that your

compost pile won’t stink!

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Although a cubic yard is often considered an ideal size for promoting conditions for thermophilic organisms, it is not necessary for composting or even for achieving a hot pile if the other factors are in an ideal balance. However, it is easier to achieve and maintain higher temperatures with a large pile. If the pile becomes too large, it may be difficult to monitor and aerate and could require more specialized equipment.

TEMPERATURE Optimum: 50-140 ºF With a good mix of carbon and nitrogen and attention to the other factors, reaching the optimal temperatures for your goals is more a sign of microbial activity than a goal in and of itself. The activity of the microbes and insulating mass of organic material surrounding the core of your pile will combine to create conditions above the ambient temperature. Mesophilic organisms, those that thrive at moderate temperatures with optimum growth occurring between 70 º and 100 ºF, are often active at the beginning of the composting process, and may become dominant as the pile cools after turning or as decomposition slows towards completion. Thermophilic organisms thrive at temperatures above 100 ºF, and, if the destruction of weed seeds or pathogenic organisms is necessary, temperatures at the upper

range (130-140 ºF) are required for sustained periods. However, at temperatures above 140 ºF, many decomposers and even some thermophilic organisms begin to die or become dormant. If the temperature goes above 160 ºF, the compost may become sterile and lose its ability to fight fungal infestations and disease. Success is not measured by the ability to maintain high temperatures; and unless there are concerns with pathogenic organisms and weed seeds, high temperatures are not necessary. Below 50 ºF, microbial populations decrease and decomposition slows, but still occurs. The speed of decomposition is one of the many processes in flux with the seasons, though the slowing in winter is much less pronounced in Southern California than in areas with long, hard freezes.

Building a hot compost pile is not necessary, but does process materials more quickly, and can kill weed seeds

and plant pathogens.

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Using a compost thermometer can be a fun, informative way to find out more about the processes going on in your pile and provide insight into how to tailor your management techniques. However, attention to temperature is not necessary for all successful composting, especially if weed seeds and potential sources of pathogens are excluded at the outset. pH Range: 5.5 to 8.0 (Optimum: 6.0 to 6.5) Typically, there is little need to worry about the pH of a backyard compost pile. Your pile will go through an acidic phase, and finished compost will end up somewhere around neutral (about 7.0), which is the level at which most plants thrive. Excessive acidity, below 5.5 or so, may indicate that anaerobic conditions are present in the pile. If your pile smells, chances are the acidity level is high, but easy adjustments can be made to increase the amount of oxygen to the pile. Using a diversity of materials is an effective way to achieve compost that is balanced in both nutrients and pH.

WHAT TO COMPOST Although the microorganisms responsible for recycling yard trimmings and kitchen scraps are capable of breaking down anything once living or made out of something once living, it’s best to err on the side of caution when composting at home, especially for less experienced or less confident composters. Some materials don’t break down very well, and others, such as pet feces, may contain pathogens that your pile may not get hot enough for long enough to kill. Excluding items like meat scraps and dairy products will still allow you to divert a considerable amount of waste from the landfill while minimizing problems like odors and pests in your home compost pile. Since every homeowner will be composting scraps unique to their living situation, diet, and landscape and put forth varying amounts of time and effort into composting, variations in results should be expected. With this in mind, we encourage you to experiment a bit and try composting different discards from your home. Here’s a partial list of materials you can easily compost and some you should probably leave out of your backyard pile.

Compost These Consider Carefully Not for Backyard Composting

fruit and vegetable scraps weeds that have gone to seed dog, cat, pig, or human feces tea and coffee grounds and bags, filters

materials heavily treated with chemicals

treated wood

bread/baked goods diseased plants plastic

egg shells noxious weeds that propagate through rhizomes or cuttings

foil, metal

expired vegetable-based sauces such as ketchup, salsa, marinara

large materials like branches, palm fronds that break-down slowly

rocks or inorganic materials

pasta, rice, cornmeal, etc. food products high in sugars, cooking grease, oils

A greater diversity of inputs produces a greater diversity of nutrients in the final compost!

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fats, or salts

stale crackers, pretzels, etc. Plants heavily infested with insect pests

charcoal ash

dried fruit Small amounts of fats, oils large amounts of dairy products

dregs from bottles of juice, wine, beer

Small amounts of cheese, dairy products

meat, chicken, fish

freezer-burned vegetables, fruits

Shrimp tails eggs

sprouted or green potatoes, onions, garlic

Cow, chicken, horse, rabbit, alpaca, sheep, goat, guinea pig, etc. manures

cotton, wool, burlap - torn Untreated wood ash (small amounts OK, but alkaline)

grass clippings Bones garden/yard trimmings spent plants leaves shredded paper (in moderation) paper towels, napkins (not used with chemicals)

less-noxious weeds before they have gone to seed

straw brush/wood chips

BE SAFE, ASK QUESTIONS, USE COMMON SENSE This list is by no means comprehensive, and you will likely develop your own list of “yes,” “no,” and “maybe” materials based on experience and tolerance for odors, pests, weeds, and risk in general. Fortunately, the list of readily compostable organics is quite long. We typically exercise caution when discussing composting with the general public. More experienced composters often choose to experiment with materials in the middle column, usually starting with small amounts and monitoring closely. When sharing composting information with others, factor in the particulars of their situation. Ask questions such as:

How long have you been composting, if ever?

Do you monitor temperature?

What type of bin or system are you using?

Do you have pets, children, or a member of the household with a particular health problem?

Where are you going to use the compost (for food crops or ornamental plants)?

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Generally speaking, experimentation is riskier for those who are new to composting, who will not know if the temperature reaches 130 ºF, who are using an uncontained system, who have family members with health concerns, and who plan to use the compost on edible or sensitive plants. Although many risks are rare, they range from the mere nuisance of smells and flies to serious health issues, so we attempt to promote careful consideration and honest, research-based discussions about questionable materials. Below are just a few examples of materials that require a nuanced discussion of how and when they should be composted:

Oleander – Toxic to animals, children, and an irritant to skin and eyes of adults. Microbes will neutralize its toxicity, so composting it isn’t a bad idea as long as you’re careful handling it and you keep children and animals away.

Eucalyptus – Okay in smaller amounts, but may take a while to break down and some research suggests eucalyptus leaves contain compounds that inhibit the germination of other plants. Older leaves that have been sitting on the ground for a while tend to decompose more quickly as do leaves that have been shredded or just rubbed in your hands.

Pine needles – With a very high C:N ratio of about 500:1, these may be tough to break down, but are compostable. Older needles tend to decompose more readily, so it is recommended to first use the needles as mulch in the yard or garden or as a thick layer of browns on top of the pile before incorporating. Pine needles are highly acidic, so if large amounts are used in your compost, it is recommended that a neutralizing source be used. For example, a very alkaline substance like wood ash could be added. Experiment with pine needles (and other very carbon-rich materials) by starting with small amounts in your pile.

Human waste – There are very stringent pathogen reduction requirements for composting human feces, also called “night soil” or “biosolids.” Human waste is compostable and many commercial composting systems do convert human waste. However, because of safety concerns and regulations, it is not suitable for a backyard pile. Composting toilets are a good option for people interested in diverting this type of waste. Human urine, on the other hand is a much more sterile material that may be suitable for backyard composting if one is feeling adventurous. Urine is a potent source of nitrogen.

COMPOST MILES We encourage composters to look closely at their immediate surroundings when searching for compostable materials. Our everyday environments (homes, schools, workplaces) often provide all the materials we need. The next step would be to coordinate with neighbors to collect any essential materials. By focusing on the areas we already inhabit, we reduce the environmental impacts of transporting materials for composting. Just as the local food movement highlights the value of keeping “food miles” low, so, too, can composters be mindful when collecting materials and ensure that the act of composting is as environmentally-sound as possible.

Your home and office are resource-rich environments! Don’t be shy

about scavenging for everyday items like wool or cotton clothing, cereal

boxes, hair trimmings, and junk mail to add to your pile!