How to Compost

 Don't Waste the Good Stuff COMPOST truck sign TO BE USED FOR WEBSITE.png

 

As we continue to roll out compost you might be wondering, what is compost? And what does – and doesn’t – go in the green compost carts?

It’s simple: food scraps and yard & plant trimmings belong in the green compost cart!

Composting our organic material helps to reduce our impact on the environment and mitigate climate change. Organic material in the landfill releases methane, a powerful greenhouse gas. By diverting that material to the composting process instead, we allow microorganisms to break it down and produce a beneficial product, putting material back into the production cycle.

View some of our frequently asked questions below, or use the Waste Directory to look up items you are unsure about. Download the Denver Trash and Recycling App or visit Denvergov.org/Cartsmart.

Click the links below to download the updated compost and recycling guidelines in English or Español: 

Video de Compostaje Correcto (YouTube)


FAQ

What are the accepted items in Denver's Compost Carts?

It’s simple: food scraps and yard & plant trimmings belong in the green compost cart!

Food Scraps: Baked goods, Bones, Bread, Cereal, Cheese, Coffee grounds, Dairy products, Eggs & eggshells, Fish, Fruits, Gravy & sauces, Meat, Nuts, Pasta, Peanut butter, Pizza, Poultry, Processed foods, Rice, Salads, Sandwiches, Spoiled or moldy food, Vegetables, and Leftovers

Yard Debris: Flowers, Grass clippings, Houseplants, Leaves, Plant trimmings, Small branches (no larger than 4 feet in length and 4 inches in diameter), and Weeds.

Bags:

  • 3-gallon or smaller countertop CMA (Compost Manufacturers Alliance) approved compost bags are accepted. No other compostable or paper bags are accepted. Click here for a list of approved bags.
  • Brown Kraft Compostable Leaf Bags (30-40 gallons) are accepted during heavy yard waste seasons only, April-June and September-November, without tape or twine – just roll down and hand crimp!
  • No other compostable or paper bags are accepted.

Which items are NOT allowed in the compost?

If it isn’t food scraps or yard & plant trimmings it doesn’t go in your curbside compost cart. Here are some common materials that are NOT allowed in the compost cart:

Paper products: including tissues, paper towels and napkins, tissue paper, brightly colored paper, paper scraps and shredded paper, tea bags, and coffee filters (please put coffee grounds into compost cart and trash the filter), pizza boxes.

All compostable packaging and products: even those that are certified compostable, including cups, utensils, plates and takeout containers.

Compostable bags: except 3-gallon or smaller CMA certified compost bags.

NO plastics, glass, metals, diapers, pet waste (even in compostable bags), treated wood, rubberbands, twist ties, produce stickers, sod, mulch, or dirt are accepted in the compost cart.

Click here to learn more about the 2023 changes to the compost stream.

 

What is compost and what are its benefits?

Composting is a biological process that breaks down organic material (like food scraps and yard trimmings) and recycles them into a beneficial, nutrient-rich soil amendment. There are different processes and methods, all which combine microbial life, water, air, and possibly heat. The City and County of Denver’s compostable materials are processed by WM and undergo a windrow composting process. The finished compost product repairs soil structure and builds entire microbial communities. Aside from vital and diverse nutrients for your soil and plants, compost also improves water retention by up to 5x. This means less water is needed, less money spent, and a healthier ecosystem is established.

In addition to the benefits of the finished compost product, composting organic material helps to reduce our impact on the environment and mitigate climate change. Organic material in a landfill releases methane, a powerful greenhouse gas. By diverting that material to the composting process instead, we allow microorganisms to break it down and produce a beneficial product, putting material back into the soil. Other important information includes:

  • Composting keeps organic material out of landfills. In a landfill, climate warming gases, such as methane, are made as organics decay under anaerobic (without oxygen) conditions.
  • Methane is 21 times more potent in its heat-trapping capabilities than carbon dioxide.; therefore, the benefits of composting organic material far outweigh the environmental “costs” of collecting, hauling and processing organic material with trucks and equipment that burn fuel.
  • Organic material like food scraps and yard & plant trimmings make up about 50% of what Denver residents send to the landfill.
  • The U .S. sent 25 million tons of food waste to landfills in 2005 — the greenhouse gas impact of composting this mass would be the equivalent of removing 7.8 million passenger cars from the road.
  • Composting is nature’s way of recycling and returning valuable organic matter and nutrients to the soil to be used again. It can be used for gardens, lawns and even houseplants, to conserve moisture and add nutrients to help plants thrive.
  • Incorporating compost into the soil can help to increase the soil's ability to retain moisture and reduce the need for fertilizers, herbicide or fungicide on farms, gardens and landscaping.
  • Compost increases infiltration and permeability of heavy soils, thus reducing erosion and runoff.
  • Compost can retain 100% of its weight in water and is an important component of gardening in a drought. 

When will I receive my compost cart?

Weekly compost collections will be phased in by Solid Waste Collection District as we get through the city. Next up is Solid Waste Collection District 4 which includes residents in Montbello, Gateway, and Green Valley Ranch. The current plan is roll out one district per quarter, prioritizing neighborhoods with lower diversion rates. You can view the rollout schedule on the map here.

As we phase in weekly compost service, we realize this may be a big shift for some of our customers. We want to ensure we are spending the right amount time to grow this service in a thoughtful way, allowing us to educate and coordinate with residents, mitigate contamination, and grow our collection routes with the new service.

We are not taking compost sign ups at this time as we continue in phases. No action is needed and you will receive a notice in the mail before your service begins with information on how to prepare.

Click here to learn more about the phased compost rollout. 

 

I'm not sure what goes in which cart. Where do I look?

Use the Waste Directory to look up items you are unsure about. Download the Denver Trash and Recycling App or visit Denvergov.org/Cartsmart.

Why can’t I compost “certified compostable” products and paper?

There are multiple reasons. For every certified compostable product (such as cutlery, tableware, cups, straws, and compostable bags) you might come across, there are several more “look-alikes” that mislead the public into thinking these items are compostable by using vague terms like “biodegradable” or “plant based" when in truth they often contain non-compostable plastics.

Unfortunately, the volume of contamination WM receives due to misleading labeling makes any packaging or serviceware items too costly to accept because of the challenge to distinguish and sort certified compostables from “look-alike” products that are not compostable.

What kind of bags should I use?

Bags are not needed in the compost carts. However, if you choose to buy compostable bags to use in your kitchen pail or green cart, they must be CMA (Compost Manufacturers Alliances) certified. The CMA logo lets our drivers and processor know that products with this label have been tested to ensure that they will compost quickly, completely, and safely. Certified compostable bags may be purchased online and at grocery stores.

What will happen if contamination is found in a load of compost? Can’t contamination be removed?

Compost loads will be rejected by WM, the City’s compost processor, and sent to the landfill at the expense of the city, increasing methane emissions at the landfill. For this reason, our drivers will NOT be picking up any compost loads deemed too contaminated to pass inspection at WM.

The city will also conduct audits of the compost carts regularly to continue to educate residents on what goes in their carts. Note that is if contamination is found (items that cannot be composted) the cart will not be collected. Misuse of the compost carts may result in removal.

The organics stream (aka compost) is not the same as the recycling stream. At a recycling plant, human sorters see contaminants like plastic bags and pull them off the sorting line by hand. Automatic equipment such as screens and optical sorters help separate materials. In comparison, by the time compostable materials arrive at a compost facility, they are already a gooey mess. Imagine pulling plastic stickers off of rotten banana peels, or even pulling plastic bags off of decaying material. A certain degree of contamination in sorted recycled products is allowable with recycling markets. Compost is not so lenient. Small pieces of plastic, glass, or aluminum will remain in the finished compost product. Farmers, gardeners, and other compost buyers need the clean, nutrient-dense food scraps and yard trimmings. But they don’t want to grow our food using compost contaminated with glass, plastic, and metals.

How can I keep my carts free from contamination between collections?

The best way to keep your carts free from contamination is to ensure that your carts are properly stored between collections. Click here to review the cart storage and set-out guidelines.

How can I compost while service is rolling out throughout the City?

As we roll out compost, we encourage residents who want to get started early or have extra yard debris to take advantage of the FREE Cherry Creek Recycling Drop-Off. All items that can composted in the curbside collection are accepted at the Drop-off during operating hours. 

Vermicomposting (using worms) and backyard composting systems are easy to use alternatives and produce high quality compost.  You can set these up at home or with community members in shared gardens!  Watch an informative video and learn the steps to amazing compost here.

Composting is great, but how can I reduce my waste?

Use reusables whenever possible. The switch to reusable shopping bags has become the norm. Keep the reuse habit going—bring your reusable mug to a coffee shop, stash a reusable set of silverware and a napkin in your bag or car for easy access on-the-go, and bring your own reusable to-go containers for leftovers. Skip the stuff and say no to disposable items like plastic cutlery and condiment packets.

Support reuse businesses. Have your to-go meal packed in DeliverZero reusable containers when ordering from participating restaurants. Reuse service companies are on the rise, with more companies no doubt coming online soon, so encourage your favorite restaurant to join a reuse program to help switch the default away from single-use disposables of any kind, regardless of whether they are recyclable, compostable or trash. 

Know before you throw. Become a Zero Waste sorting pro. Check the Waste Directory to see if your to-go container is recyclable. Do not recycle “compostable” to-go containers. 

Learn more tips and tricks for waste reduction and reuse here.

What happens to compost after collection?

The organic material collected through the Denver Composts program is sent to a commercial composting facility in Keenesburg, Colorado that is run by WM. There, organic material is ground into fine pieces by an industrial grinder and then composted under controlled conditions, so it can break down quickly and contribute to making quality compost. After composting is complete,  WM performs a number of analytical tests on the compost, using an independent laboratory, to ensure the compost is a quality product before selling it.

Solid Waste Management offers bagged and unbagged compost for sale back to Denver Residents at a discounted price each year at the Annual Mulch Giveaway & Compost Sale.

It is now easier than ever to close the compost loop and return finished compost made from the materials collected in Denver’s green compost carts back into your soil.

How do I manage odors or pests around my green compost cart?

Compostable material does have a smell. It’s the same stuff you put in your garbage, but now it’s just in a different container. Odor is often caused by too much moisture. You can minimize odor by:

  • Ensuring you set your cart out for every collection.
  • Draining as much liquid as possible from organic material.
  • Keeping your cart clean.
  • Burying your food waste underneath some yard debris.
  • Wrapping food scraps with newspaper or placing in a paper bag before putting it in your cart.
  • Freezing leftover meat and fish scraps and waiting to put them in your cart until your collection day.
  • Waiting to clean out your refrigerator until the day before your collection day, rather than the day after.

The green composting cart is designed to be pest-resistant with thick plastic and a tight-fitting lid. Compost can attract fruit flies, so be sure to keep the lid closed. If you have problems with bugs and rodents around your trash now, you may experience some problems. If you do not currently have problems with pests, you should not experience any additional problems with your green cart.

It is the resident’s responsibility to clean their cart. A simple rinse with the hose every couple of weeks should keep the cart clean. A great idea for cleaning your green cart is to use a broom to reach the bottom.

 

How do I manage over-sized yard debris

All branches or limbs placed in compost carts must be no longer than 4 feet in length, no larger than 4 inches in diameter, and no more than 50 pounds per piece.

Logs, stumps, and other larger yard debris are NOT accepted in the Denver Composts Program.

For information on dropping off larger yard debris materials visit Cherry Creek Recycling Drop-off.

How do I use my kitchen compost pail?

  • Store your kitchen pail under or in the sink or on the counter to make it easy to access while preparing food or cleaning up after a meal. Find a new spot for your garbage pail so that you have to think before you throw something away - ask yourself, "Can this be composted?"
  • Dump the contents of your kitchen pail into your green cart at least once a week.
  • Drain as much liquids as possible from food before putting it in your kitchen pail.
  • Rinse out your pail after you empty it or run it through the dishwasher on the top shelf to keep it clean and fresh. (WARNING: Running your pail on the bottom shelf of your dishwasher will cause the pail's lid to warp and not close properly.)

Should paper go in the compost or recycling?

  • Paper products should not go in the green compost carts. Check the Waste Directory to see what paper products, like cardboard and office paper, should go in the recycling cart!
  • Many paper products like tissues, napkins, paper towels, coffee filters, and pizza boxes can be composted in backyard compost. Learn more here!

Garbage disposal vs. composting?

There are no real environmental benefits to disposing of food waste through the wastewater system.  In fact, it requires extra water usage to do so.  Also, food waste can be the source of many plumbing problems.  Disposing food waste through a garbage disposal increases the likelihood of clogs, especially if the food waste contains unsaturated fats, which solidify at room temperature and can build up inside pipes.

Placing food items in your green compost cart is a better alternative both environmentally, and for your home.  Backyard composting is good too, just no for the meat or fat items.

Are businesses and apartments eligible for compost collection?

Expanded Waste Services apply to residential customers of Denver’s Solid Waste Management division. For information about Waste No More, which applies to apartment complexes, restaurants, office buildings, and other commercial facilities, visit the task force page.

Solid Waste Management is only authorized to provide services to residential homes of seven or fewer units and our own municipal facilities. DOTI is not authorized to provide services to commercial properties such as businesses and apartment communities. Please visit our Apartment and Multi-family Recycling page for information on trash, recycling, and compost at these buildings.

Ordering Take-out? Here are some composting tips.

  • Compost all of your food scraps!
  • Trash the serviceware and paper products! These items are no longer accepted in Denver’s compost carts. Better yet, refuse these items when you can. Waste reduction is the best strategy and eliminates confusion!
  • Make sure small plastics (i.e. condiment packets, straws) aren't accidentally thrown in your green cart.
  • Go to the Skip the Stuff website for more information on how to help alleviate contamination when ordering out or eating in.
  • And remember, when in doubt, throw it out! Let's keep contamination out of our green carts.

Backyard composting vs. compost collection service?

The organic material collected through the Denver Composts collection program is sent to WM's commercial composting facility. There, organic material is ground into fine pieces by an industrial grinder and then composted under controlled conditions.

So materials that you wouldn't normally put in a backyard composting bin, such as meat, bones, and processed foods, can break down quickly in a commercial composting facility and contribute to making quality compost. After composting is complete WM performs a number of analytical tests on the compost, using an independent laboratory, to ensure the compost is a quality product before selling it.

We encourage you to continue backyard composting if you're already doing so. These systems work great together! You can still compost lots of materials in your backyard while putting your meat, dairy, grains, and excess yard waste out for pick-up in your green compost cart.