Composting has many benefits and many virtues, which is why it is becoming continually more popular in the united states and around the world. It is sustainable and environmentally friendly, a wonderful activity that can connect people, and especially children, with nature and the life cycle. But sometimes its, well, stinky! Compost odors present in indoor compost bins are especially irritating, but outdoor compost odors are no picnic either. In this article, we will look at several of the common problems that produce nasty odors in compost bins, both indoors and outdoors, and make some suggestions as to how to achieve the Odorless Compost Bin!
Outdoor Compost Bin Odors
Odors in outdoor compost bins are commonly caused by a few common compost issues, such as improper temperatures, a bad ratio of nitrogen to carbon, and infrequent turning of compost. We will discuss each of these in this section.
Nitrogen to Carbon Ratio
Having a nitrogen to carbon ratio that is way off target can impact the success of your compost process. This imbalance can slow decomposition and produce nasty odors. As a rule of thumb, nitrogen sources are usually green in color, and carbon sources are usually brown in color. Typically, users should be aiming for a 75% nitrogen to 25% compost ratio for optimal composting (note: your composter may vary, and if so, follow the instructions for your specific composter).
The primary sources of nitrogen in composters are grass clippings and kitchen scraps.
Between your grass clippings and the kitchen scraps you have pulled out to compost, you should aim for about 25% of the total volume of humus you’re working with to be made up of these materials.
Most any kitchen scraps will do, though typically meats and dairy products are not used in outdoor composting.
Carbon sources for compost include leaves, straw, and newspaper (shredded).
Leaves and straw are a very effective carbon source, though ideally they should be broken down into smaller pieces before composting. By running a lawnmower over the leaf pile before composting, the process will be sped up and the results will be better. Use a garden mulcher to chip up your yard waste
Newspaper can also be used, though it must be shredded before it is placed in a compost bin. The inks used in modern newsprint are not a concern, either black inks or colored inks, and newspaper is a safe compost material. Shredding all of that newspaper can be a chore, though!
One other aspect to note is that you want to be sure that the compost bin humus is moist, but not soggy. If your humus is too dry, it won’t process. If it’s too wet, it will become slimy and nasty. Add water or compost materials as needed to properly balance the moisture level.
Improper Compost Temperature
In order to keep your humus ticking along, you want to aim for a minimum compost temperature of around 60’F, and you want to keep your maximum temperature below about 170’F.
For an outdoor compost bin on a reasonably warm day, it’s not too difficult to achieve temperatures of 60′. And as long as you’re not trying to compost in the Arizona desert sun, keeping the temp below 170′ isn’t too difficult.
(Note: if you are composting in the Arizona desert, you probably want to keep your bin in the shade during the hot months!).
For most users, temperatures that are too low are more common than temperatures that are too high, and this can lead to unpleasant odors due to stalled composting.
By using a black compost bin, placed in the sun, you can use the heat-absorbing properties of a black bin to increase the temperature inside the compost bin above 60′. A compost bin such as the black colored Redmon Green Culture 65 Gallon Compost Bin (shown here) is ideal.
Infrequent Compost Turning
Humus needs to be regularly mixed in order to encourage the microbes to break down the materials to produce a great compost. Depending on the design of your compost bin, you will need to mix your compost more or less frequently.
Ground-Based Compost Bins
If you’re using a standard ground-based compost bin such as the Geobin Compost Bin shown here, you want to be mixing your compost typically every 3-7 days in order to produce a high-quality result.
Mixing less frequently than this can result in stagnation, and off-putting odors, so be sure to regularly go out and mix your compost.
We know that getting the shovel or the pick out to mix the compost can be a chore, and a dirty process, so if this task is a pain point for you, you may want to consider a tumbling composter. These products are typically more expensive but provide several benefits over ground-based bins. See our article on Compost Tumblers vs. Bins for more information.
In general, we are fairly fond of tumbling composers due to their ease of use, their compact design, and the speed and efficiency in which they process compost materials. They also tend to be rodent-free, pest free, and less prone to odor than open-air compost bins are. Tumbling composters such as the Lifetime 60058 Black Compost Tumbler (shown here) should usually be rotated every few days for an ideal result.
Indoor Compost Bin Odors
Indoor Compost Bin Odors are a different beast than outdoor compost bin odors. They are more irritating due to the fact that they tend to be located in and around where people live. Depending on the style of compost bin you use indoors, there are different ways to combat compost odors.
Traditional Indoor Compost Bins
Indoor compost bins are pretty simple and are usually a sealed plastic or metal bin, such as this OXO Good Grips Kitchen Compost Bin [Amazon Link] (shown here). These kitchen compost bins should be emptied at regular intervals. This is where the problems tend to manifest. If you leave kitchen scraps in a compost bin for several days, each time you open the bin, it will smell rather unsavory!
This is especially an issue during winter time when going outside into the frigid night air to dump the compost bin after dinner isn’t exactly an appealing task. It’s easy to let the compost bin sit for several days in this circumstances, and that’s when the odors become an issue.
The good news is, assuming you don’t have any cracks or a poor seal in your compost bin, usually, the bin won’t smell unless it is opened. If your bin is releasing odors even when closed, it’s probably time to pick up a new kitchen compost bin! Alternately, you could consider moving to Bokashi style composting.
Bokashi Compost Bins
Bokashi Composting is a different style of composting than traditional composting, and it originated in Japan in the 1980s. The first phase of Bokashi composting typically occurs indoors and is unique. This system uses a mix of a microbe-inoculated Bokashi bran and a blend of food scraps to produce a bokashi tea and bokashi compost.
Bokashi composting has some significant advantages over traditional composting, and some disadvantages too. One of the biggest advantages is the fact that, when properly executed, the bokashi bran masks any significant nasty odors, and any odor from a bokashi bin (such as the Chef’s Star Bokashi Bin System shown here), when opened, is something more akin to a pickling smell than a rotting smell.
Bokashi buckets are always sealed, anaerobic systems which create an environment where compost is processed (and we should note that meat and dairy can be composted in these systems, unlike other compost systems).
The downside of Bokashi composting is that you need to acquire a regular supply of Bokashi Bran. You can purchase bran, or you can make your own.
Achieving the Odorless Compost Bin
Achieving a relatively odorless compost bin is not terribly difficult, as long as you follow a few simple rules. For outdoor bins, be sure to keep your temperature in the proper range, aim to achieve the right ratio of nitrogen and carbon, and be sure to turn your compost regularly to keep everything mixed properly.
For indoor compost bins, be sure to empty your bin as frequently as possible, especially during the winter when it’s tempting to not go out into the cold to empty your bin!
You could consider using a Bokashi system for indoor composting, and combine it with a traditional outdoor system, which would allow you to compost more types of food (meat and dairy), and speed up your compost process.