Aerobic Container Composting
Outdoor microbial composting in the desert... on a balcony!
Microbial Composting (MC) is the go-to for balcony composting in hot environments. While most composters find the winter months more challenging, in the desert, here the summer poses the biggest challenge. With temperatures firmly in the 40s to 50s C (100+ F) for at least four months per year and no soil to lend its beneficial microbiome, the MC process needs to be amended for the desert climate. However, using the MC method to make rich, nutrient-dense compost in the desert is easy and achievable!
Benefits of composting in the desert:
It’s hot: Compost is ready much faster than in temperate climates.
Nutrient recycling: Return badly needed nutrients to the garden.
Waste reduction: Waste breaks down very slowly without moisture; decomposing your own waste reduces the amount you throw out.
Free fertilizer: Deserts are always needing more nutrients- supply your own much more cost-effectively!
Fascinating experiment: It literally changes every day and it is endlessly surprising as to what the microbes get up to!
The Devil is in the Details
Most DIY MC composters will recommend that you drill drainage holes for liquid to drain out of the bottom of the composting vessel. In hot, arid environments, however, moisture is critical to maintaining the microbial community that will break down your compost. These microbes won’t survive without a ‘Goldilocks’ level of moisture and since it is more liable to evaporate, it is best to leave the MC environment intact.
A lack of drainage is beneficial for more than retaining moisture levels; MC leachate is likely to be smelly and attract flies, which invites an unwelcome life cycle to the process. Leachate disposal also becomes a problem, especially since domestic plumbing is not equipped to deal with the problem and hot, arid climates lack the soil to absorb the excess nutrients.
With balcony/apartment composting it is important to keep the entire process as discrete as possible for the benefit of the whole community.
MC is composed of two main ingredients: Nitrogen (‘greens’/ fruit & vegetable waste) and Carbon (‘browns’/ paper, cardboard, dried leaf matter). Different composting websites will advise different proportions of greens to browns but for balcony MC in the desert, it is advisable to adjust this practice slightly.
Unless you are able to weigh your greens before you add them to your compost bin, it is difficult to add the ‘right’ amount of browns – and the proportion will vary depending on the ambient temperature and humidity levels. Unless you get excited about constantly recalculating your proportions, this is not the most efficient way to get started with MC in the desert.
Instead, because it is so important to maintain as much moisture as possible in a hot, arid MC environment, simply add as much shredded browns to absorb any excess moisture. Though it may sound vague, when practiced it makes the most sense. As you get to know your compost better, you will be able to tell what ‘too much moisture’ looks/smells like and when it needs more greens or browns, which you can adjust accordingly. Trust yourself!
This is the key element to successful desert MC. Many composting websites for temperate balcony MC advocate turning the compost every couple of weeks and disposing of the leachate when necessary. Great- but there is so much more to maintaining a healthy and productive desert compost pile! Luckily, it’s incredibly easy to do.
Decaying matter will release gases as the bacteria, fungi and microbes break down molecular bonds of the decomposing material. Some of these gases are unpleasant but most of them are produced by anaerobic bacteria. Anaerobic bacteria are organisms that thrive in the absence of oxygen and proliferate when their environment is compacted and overly saturated. A typical example of this is decomposing ‘green’ fruit and vegetable matter that has become an unrecognisable furry sludge at the bottom of the bucket – you already know it smells bad before you get anywhere near it. It looks like and has the texture (but sadly none of the aroma or taste) of undercooked brownie. (Usually, this is the source of any leachate that will drain out of the bottom of the bucket in a temperate environment. Nice.)
There are two easy solutions to combat this issue:
Add more browns. Don’t worry about specific ratios- as matter decomposes, it will release varying amounts of liquid. Add enough browns to absorb any excess moisture. How can you tell if you have excess moisture?
STIR. Get an old broom handle or half of a shower curtain rod or a stick of rebar- anything that’s sturdy and fluff that up. Check to see what’s at the bottom of that pile. Break up clumps. Mix dry matter in to the wet. Get air into every pocket of that pile. Plunge in there and get things moving!
The heat in the desert provides a great environment for decomposing microbes – the heat really speeds things up! However, the right proportions of agitation, water and air are crucial for successful MC. Personally, I have found it necessary to stir the compost every morning and every evening, especially during the summer. This will limit the population of anaerobic bacteria and encourage the aerobic bacteria(organisms that thrive in oxygenated environments) that will more discretely break down the compost – that ‘earthy’ smell is usually them fighting the good fight. Some light decomposition odours notwithstanding, this has kept my piles smelling earthy even in the early stages of composting.
If I have been lazy or away on holiday, the pile will compact itself under its own weight, transforming the environment in the bucket and allowing the anaerobic bacteria to take over from the aerobic bacteria. When I take the lids off, the decomp is… noticeable! However, lots of stirring and fresh air rebalances the environment in favour of the aerobic bacteria and they take care of the problem within 24-48 hours.
If you are lucky enough to have the space for one of those self-contained rotating drums, please do use it- they’re great for mixing up matter. However, they do limit the amount of fresh air that can access your pile while you are doing the mixing. So far, the best equipment appears to be a bucket and a stick of rebar. It’s nice to keep things simple, cost effective, environmentally friendly and accessible.
How do you know if you’ve got it right? To quote a certain well-known Toucan, follow your nose!