Thoughts on the Subpod

In 2019, a crowdfunding campaign helped introduce the Subpod into vermicomposting community. Although the concept of the Subpod isn’t new, it does provide a prefab system that is easy to set up and maintain.

Image from Subpod media kit

The main idea behind the Subpod is to create compost right where it is needed. It is an “in-ground” vermicomposting set up where one can garden and compost all in one spot.

Let’s dive into some of the features and benefits.

The Subpod is made from polypropylene plastic (#5 plastic) that is BPA free, food grade, and can be recycled at the end of its use. Plastics used in the garden (even BPA free ones) can have some negative impacts on the environment. For those interested, here is a YouTube video from Canadian Permaculture Legacy that goes into a lot of detail about use of plastics in the garden and landscape. Also, #5 plastics may not be recyclable in one’s area. Check out this summary form Ecolife on polypropylene.

The Subpod contains two chambers. One for adding food scraps and the other for adding the worms. There are holes between the two chambers that allow the worms to move between them and provides airflow. Also the entire perimeter of the system has holes that allow airflow. This is definitely a benefit of the system. Since composting in general is quicker and less stinky with aerobic conditions, the openings are a plus.

The original Subpod is quite large at 30″L x 18″W x 17″H. There is a mini version that measures 18″L x 20″W x 17″H (please note these are approximate dimensions). Although I think the size in both cases is reasonable for vermicomposting, the one drawback is that once it is in place it becomes difficult to move. So planning out the location beforehand is essential.

Subpod also offers a bundle package that includes the raised bed. As a prefab purchase this is very convenient. However, I do want to point out that the actual garden space is very limited. So one might want to build a larger bed especially if growing plants with a lot of biomass (tomatoes for example).

Here are some of the benefits of the system:

  • Prefab all in one package – no need to build your own system or purchase multiple items to set it up
  • Easy to set up – easy directions to follow and well designed
  • Barrier against pests – (moles, voles, and other digging animals) even lockable for protection against raccoons
  • Good airflow for aerobic vermicomposting conditions – no need to drill holes into the system
  • Aesthetics – the Subpod is a great looking system and much nicer than many DIY style systems
  • Easy to add food scraps and bedding – this is similar to all other vermicomposting systems
  • In ground system – this is a major benefit as the surrounding soil acts as an insulator against temperature swings
  • Lid – comes with easy instructions how to set up and operate but also acts as a barrier to rain and the elements
  • Moisture – if the system was set up in a raised bed (and not buried in the ground), the system can drain quite well and won’t have excess moisture
  • The vermicast is already in place – there isn’t a need to move the finished vermicast as it is right in the root zone
  • New vermicomposters! – This simple design has introduced vermicomposting to a whole new group of people. The more people that compost food scraps, there will be a reduction in lost resources to landfills.

There are some cons to take of:

  • Cost – this is an expensive system to purchase and doesn’t include price of worms
  • Garden Seat – OK so this may be a benefit too, but by using it as a seat it reduces the amount of plants you can use in an already tight raised bed
  • Worm quantity requirement – the Subpod directions indicate that one needs a minimum of 1,000 worms to start. However, this depends on the type of worm (ANCs would require fewer) and not all quantities are the same! I believe the directions are really calling for a pound of worms and not specifically 1,000.
  • Worm flow – the creators claim that worms will leave the Subpod to the surrounding soil in the bed. However, that is NOT composting worm behavior. Composting worms would only leave the system if conditions are poor (too hot, cold, wet, lack of food, etc.) Also, there is a claim that when the worms are in the surrounding soil, they will help aerate the soil. Compost worms do NOT do this. Compost worms are Epigeic and do not travel into the soil. Earthworms which are NOT compost worms are soil dwellers and aid in aeration. Here is a site that explains the differences.
  • Location – planning out the location of the system is vital for this to work. One of the problems is that a vegetable garden typically requires full sun (or mostly sun). The worms can handle some higher temperatures but may need some shade in the afternoon. There are some competing priorities with operating a vermicomposting system and a garden.
  • Climate – this is dependent on where you live. In the Northeast, the worms will thrive in the late spring through the mid-fall. However, the winter can kill off the worm population. This is about expectations. Don’t expect to be able to operate at full capacity in the winter. Many worms won’t survive and the cocoons may or may not be viable come next spring. Other climates will have their own specific challenges.
  • Roots – this will be a challenge with this system. Anyone who has created a compost near a tree or shrub will understand this. The roots of the plants will travel into the system to access the vermicast and moisture. This will make it difficult to move any finished vermicast to other parts of the garden. Although this is a benefit to the plants, there will some maintenance to remove the roots at the end of the season. If not, the holes will get clogged overtime.

It may seem that I have more of a negative view on the system but that is NOT true! I think the system can work really well but the expectations on running an outdoor system have to be spelled out. Swings in temperatures and amount of humidity can affect worms greatly and beginners often don’t have the skills to deal with this. However, I think the Subpod can make a great secondary system. The system’s popularity will also help more people to start vermicomposting and reducing food waste going to the landfill.

The in-ground vermicomposting concept

Earlier, I mentioned that the concept of the Subpod wasn’t new. The concept of having the vermicompost system next to or in the garden growing area. Many of the DIY versions used 5 gallon buckets with lids or the use of trenches. The trench method used by Bentley Christie of Redwormcomposting.com is probably the simplest system as it only requires a shovel…and a lot of hard work. However, the major benefit is that it will improve the soil dramatically.

The 5 gallon (or 6 gallon bucket) system is also a good option. It is far cheaper than the Subpod but it will take some time to set up. One of the main benefits of this system is that it can be moved around. So you can move these around to various spots of the garden after each use. Also, since it is cheap, multiple systems can be made and can be set up in multiple spots. Here is Bentley’s version of the bucket. Here is The Nakid Gardeners version.

Another option with buckets is to make a DIY grow tower. Mark Paine of EVE Growing has created multiple designs of these DIY towers. He uses buckets and even larger 55 gallon drums that grow plants and have active vermicomposting. These systems may not be aesthetically pleasing but they do work!

Worms for the Subpod

Overall, I think it is much easier to use red wigglers for an outdoor system since they can adapt to a greater range of conditions compared to ANCs or ENCs. Also, I think it’s also important to note that worms will need some time to acclimate to any new environment and outdoor systems can pose a challenge with the acclimation period. If you add the worms too early (in colder weather under 50 degrees), they make take longer to acclimate and reproduce. The sweet spot is typically when temperatures are reliably in the 60’s (late April or May in the North east). Adding the worms too late in, June or July, the worms may not be able to create enough vermicast to benefit the early plants like radish, lettuces, and peas.

The makers of the Subpod indicate one should start with 1,000 or 2,000 worms. That may be OK but beginners get the impression that is an exacting requirement. Red wigglers approximate 1,000 per pound but that is fully grown adults. Most sellers of worms by weight or count use an approximation and don’t count worms individually…if they did their costs would go way up! Since the worms are often shipped in peat moss, to get the microbial activity going in a Subpod will take extra time.

This is where I think the Starter Worm Mix is actually a better product to use than worms by weight. Since the Mix already contains the beneficial microbes and has a wide variety of worm sizes, it allows the worms to adapt faster to the new system. The other plus is that the Mix already contains vermicast which will help get the plants off to a quicker start. Given the size of the system, it might be better to purchase two bags of the Mix. This will provide plenty of worms and get the system moving along much quicker.

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