California Department of Resources Recycling and Recovery (CalRecycle) 

Organic Materials Management

Community-scale composting

If you cannot compost at your own home, or if you simply want to expand composting in your area, a community-scale composting program is a terrific way to increase local resilience, build sustainability awareness, and provide quality soil amendments for local use. Food scraps and yard trimmings can easily be turned into beneficial compost for your community garden or local urban farm. Especially for apartment dwellers, community-scale composting is one approach to preventing landfill disposal of compostable organic materials. It has the potential reducing waste generation and benefits the earth by returning nutrients to the soil. Your program can also engage and enhance your community or a local school with a fun educational experience.

There are many aspects to a sustainable community-scale composting program. You may decide to take only some of the steps or form partnerships with private or public entities to close the loop.

If your community scale project is a success and it grows larger, at some point it may qualify as a State regulated compost site. If your project has more than 100 cubic yards of compostable material on the site at any one time, and/or the pile(s) of material take up more than 750 square feet of area, you need permission from your local environmental health department. Local environmental health department personnel who enforce California state laws and CalRecycle regulations are known as the Local Enforcement Agents or LEAs. CalRecycle’s Local Enforcement Agency Directory can help you find the LEA for your area.

How to start a program

Define path and goal

Create a vision for the project. Because of the many potential participants in a community-scale composting program, you will want to define some goals to make sure you stay on track. Find a location such as a local urban farm or community garden where the compost will be made. For larger programs, you may want more than one location. Get the word out to participants and plan a way to keep your community informed.

Some cities and counties provide assistance for backyard and community composting. This may involve simple classes in composting basics, free bins for backyard-sized piles, or even paid city personnel who assist or manage community gardens. For instance, the City of Sacramento Department of Parks and Recreation operates 15 community gardens. Santa Clara County operates a Master Composter program. In Los Angeles, the non-profit LA Community Garden Council may be able to offer advice on which gardens need more composting. In San Diego, the Community Garden Network has a similar role. You may be able to take advantage of a master gardener program if your area has one.

Neighborhood associations and social media are a great way to gauge interest and potential support for your community-scale composting program. A simple survey for your neighbors can be used to see who is interested in a program, what materials they wish to compost (food, yard waste, shredded paper, etc.), what quantities may be available, and if people are willing to pay for a program or volunteer their time. Smaller cafés, restaurants, juice bars could also be a valuable source of clean, consistent feedstock material; however, poaching paying customers from franchised waste haulers can lead to problems, so it is best to understand local laws, know the local players, and discuss these types of issues with local recycling coordinators or others in the know. CalRecycle maintains a directory of local recycling contacts, which can help you find the entity or person who can answer basic questions.

Check with your local government

Once you have come up with a plan, share it with your local recycling coordinators, community garden liaisons, or others who might have an impact on your plans. Cities and counties typically have franchise agreements: binding contracts with private companies that entitle those companies to the solid waste generated within their borders. Some cities may have rules regarding community-scale composting.

In addition, many counties license solid waste haulers, and picking up food waste from residents—even on a bicycle--may require you to obtain such a license. Another option might be to organize your composting group as a co-operative, charging participants a membership fee where pick-up of feedstocks and delivery of finished compost are included. Be open-minded to changing your plans before you start involving your participants.

Containers for participants

For households, there are many convenient commercially available bins to place in the kitchen, on the counter, under the sink, in the freezer, etc. The best containers provide aeration, which reduces odors, but with holes too small for insects like gnats and fruit flies to pass. Keeping the container in the freezer until it is emptied can also reduce odors and pests. Suitable containers will be leak-proof and could vary in size from one quart for a small apartment kitchen to as large as five gallons for a neighborhood café or juice bar. To keep costs down, participants can provide their own containers. Try branding your compost project by offering your green waste donators a reusable five-gallon bucket with a sticker or stencil print of your logo.

If you have participating businesses, they may need larger containers that can safely accommodate larger volumes. Consider the amount of material before purchasing or even limiting a business’ food scrap contribution to specific materials (for example coffee grounds or juice pulp only). For most composting methods, you will want only the pre-consumer food scraps from the kitchen and not leftovers from the dining room, unless contamination is tightly controlled.

Make sure to continually educate your participants on acceptable materials either through a website, flyers, or with information pasted on the collection containers themselves. For community-scale composting, avoid fats, oils, and grease (FOG), meats, and dairy, as they increase the potential for odors and vectors (see CalRecycle regulations, Section 17810.4. Excessive Vectors).

Pick-up or Drop-off

Decide if your program can legally provide pick up or will encourage participants to drop off materials. In a pick-up system, participants generate materials and set out the container at their curb, doorstep, or porch, similar to curbside waste and recycling programs. Someone in your program would then drive or bike around, emptying each container into a larger collection bin, and bring the material to where it will be composted. If you have reliable volunteers or can pay your collectors, you could choose to use cargo bicycles for the most eco-friendly approach. There are many successful bicycle-powered community composting programs, including these:

Cars and trucks might be preferred, depending on your landscape, climate, or distance traveled to compost. No matter your collection method, if you provide a reliable service, a pick-up system is very convenient for participants and usually results in higher participation rates. However, pick-up systems can generate the need for a solid waste hauling license, as previously mentioned.

You can choose not to offer a hauling option and instead allow participants to drop-off their material at the composting site. You will need to set hours and have someone monitor the drop-off site to ensure that material does not create odor or vector problems. Immediately covering the delivered material will help reduce smells, discourage flies, and in general prevent problems with neighbors. Heating the compost up quickly will minimize the time these materials remain attractive to vectors.

Achieving feedstock balance

If you are collecting food wastes, you will need a high-carbon material to attain a balanced mix. The carbon source offsets the nitrogen in the food, provides a bulking agent for better aeration, and serves to absorb the liquids in food, thereby reducing odors. Straw, sawdust, leaves, or shredded paper can work. If you are using woody material collected from local landscapes, it may need to be chipped into smaller pieces. Small gas or electric chippers can be very convenient for shredding or size reducing materials, resulting in better composting; however, they require maintenance and can present safety hazards for users.

Choose a composting method

Check out CalRecycle’s guide on building your own compost bin. This could be a fun way to involve volunteers, which will increase their commitment to the overall program.

If you are not as comfortable with building a bin, there are number of ready-made compost bins that may suit your program.

For more ambitious programs, or ones that compost a lot of food, aeration will be the key to reducing odors, speeding decomposition, and avoiding excess labor turning the piles. Designs for simple aeration systems can be found on the internet. Some compost system vendors design and sell more sophisticated aerated static pile systems, which look good, help keep the composting site looking and smelling clean and might even use things like solar power to provide aeration. Without aeration, you will need to turn the material regularly, which can be hard work.

If you have ample funding, an in-vessel system can produce mature compost fast and provides a better way to reduce odors and prevent vectors. In-vessel systems can range from tiny hand-turned tumblers to more sophisticated systems that handle a few dozen to hundreds of pounds of feedstock per day. Some of the more deluxe systems can cost many thousands of dollars.

Remember that if you create odors, or attract rats or other pests, this could generate complaints from neighbors, which could result in your composting operation being shut down. So be sure to manage your pile proactively, keep your neighbors in mind at all times, and ensure worker coverage when key personnel are away on vacation.

Make Compost!

Compost will happen on its own wherever compostable materials accumulate. It is a complex biological process involving a succession of microorganisms, each with its own unique role. Human intervention can speed up the process, make it more efficient, and ensure the pile gets hot enough to kill pathogens and weed seeds. This generally involves building a pile with the right mixture of carbon and nitrogen, maintaining a certain amount of moisture in the pile, and ensuring air can reach the pile’s center. These goals can be accomplished through system design and forced aeration, or through manual action.

CalRecycle’s home composting web page is a good source to start with.

To learn even more, look into a Master Composter class, typically put on by the UC Master Gardener program in your community, which can provide certification and training. Other places to learn about composting include training through local sustainable landscaping groups, training through your local University of California extension office, or comprehensive composter training put on by the U.S. Composting Council.

Also, you may wish to complement your composting operation by adding vermicomposting, which can provide a fun educational opportunity and produces worm castings, one of the most valuable soil amendments.

Kern County is one of many local agencies that promote back yard composting.

LA Compost has a simple brochure that addresses many key composting issues. There are many examples of such brochures on the internet; here is one from a garden in Brooklyn, NY.

The Sonoma Compost Club is an innovative group that installs composting sites at schools.

In Stockton, the non-profit group Puentes is developing an urban farm to increase food security and healthy diets in under-served communities.

Find an “end user” for your materials

If you are composting at an urban farm or community garden, it is likely most or all of your compost will be used there. For situations where participants choose to receive compost in exchange for source separating their food scraps, you will need to measure how much food scrap material is collected and define how much will be traded for finished compost. Consider partnering with local restaurants, cafes, and shops for vouchers or coupons for participating residents who may not need compost but wish to contribute to a more sustainable environment.

For a very thorough guide to community composting program, including details not mentioned here, such as budgeting and food scrap estimation, check out this publication by the Institute for Local Self-Reliance.

Organic Materials Management Home

Last updated: June 30, 2017
Organic Materials Management http://www.calrecycle.ca.gov/Organics/
Contacts: http://www.calrecycle.ca.gov/Organics/Contacts.htm