Does a Compost Bin Need to Be in the Sun?

Does a Compost Bin Need to Be in the Sun

One thing about compost bins is that as the season gets on, they become heavier and heavier. Once your bin is mostly full, it can be hard to relocate without damaging your yard or risking making a mess. That means your initial bin placement is kind of a big deal.

Since a compost pile is an element of the garden and the composting process is related to plant processes, compost heap placement can be sorted by sun or shade. When speeding up the decomposition process, does direct sunlight help break down organic matter faster, or is shade a better location? Find out all that and more below!

Is Shade or Sunlight Better for Compost?

Generally speaking, the hotter you can get your compost pile, the more effective the composting process will be; therefore, intense sunlight can be beneficial. However, the composting process also needs to be sustained for a certain amount of time to break down weed seeds and pathogens and give nutrients a chance to bind to the soil. Excessive heat can kill off beneficial microbes and lead to dry compost piles, both of which slow down the decomposition of organic matter. 

Compost placed in the shade may struggle to reach 140°F, the minimum temperature needed to destroy harmful materials in the compost pile. Insufficient sunlight can also lead to moisture buildup and the spread of anaerobic bacteria. If excessive moisture and insufficient aeration occur, your compost pile will develop an anaerobic environment and put off a foul odor. In a hot climate, shade can keep your moisture levels higher for longer and reduce the need to add water and additional green materials.

In cold climates, a sunny location can keep your compost active longer into the year and keep up with your kitchen scraps over the winter months. In hot climates, partial sunlight can lead to faster decomposition during the hours of sun and a stable level of moisture when not in direct sunlight. A compost near a deciduous tree will give you light shade during the summer and full sun all winter for a bit of warmth.

Is Sunlight needed for Compost to Break Down?

As long as microbes exist to break down organic materials, you will be able to get compost. Compost made without aerobic bacteria, sunlight, or a balance of brown materials may take longer to break down and have an ammonia odor. For a faster-finished product, a well-balanced compost heap or compost tumbler will need partial sunlight to break down food waste and fresh grass. 

For organic waste like manure, you can opt to do a cold compost over the winter. Regardless of how hot your compost gets, cow and horse manure works better in aged mature compost. Letting a cold compost sit for 6 months or so will result in an excellent compost mix without the need for sunlight.

Compost Bin in Sun

Hot Compost

Nothing turns food waste into compost faster than heat. When compost heats up, the microbes reproduce rapidly, and the less beneficial organisms die off. As the compost goes through the last of the organic materials, the bacteria die off the temperature drops. Organisms can also quickly consume all the oxygen in the pile and begin to suffocate.

It is important to constantly turn the compost pile or add aeration to keep the microbes from dying off before the food scraps are broken down. Every time you turn the pile, new bits of matter are exposed to air, and the bacteria population explodes. Hot compost uses up moisture very quickly, so you will need to apply water or compost when there is ample rain. 

Many different materials are thrown into the compost, some are basically sterile, like coffee grounds, and others can harbor hazardous pathogens such as those on animal waste. Few things sterilize better than heat. Everything from weed seeds to e. coli can be burned up in a properly built and maintained hot compost pile. For complete safety, you will need to keep your pile at between 140-160°f for 3 to 4 days.

Cold Compost

When heat is not an option, your next best composter is time. Filling a bin with the right composting materials in ratioed layers can build a pile that will break down and sustains itself for several months. This can be useful when trying to achieve a richer compost pile in colder temperatures. 

As bacteria and microorganisms in the soil heat up, they eat and reproduce and eat some more. Unfortunately, at the atomic level, they take from the compost what is meant for your plants, and so the more organisms you have breaking down your compost, the fewer actual compost nutrients you will have for your soil in the end. If you do a job yourself, you keep all the money, but if you hire help, they get their share; soil microbes are exactly the same and eat your nutrients in return for breaking down food waste.

If you allow organic materials, especially manures, to break down slowly over months to a year, the resulting compost will have a higher nutrient density than hot compost made with the same composting materials. Cold compost should still be turned at least once every 3 months, and moisture added whenever needed. Even though you let the compost pile mature, you may still have weed seeds and fungus spores that live for years viable in your soil; these can only be killed in a hot compost or with treatments. 

Pros and Cons of Having a Compost Bin in the Sun

ProCon
Faster DecompositionDrys Out Quickly
Kills Weed SeedsIncreases Food Smells
Kills PathogensDecreases Compost Nutrient Density
Kills Fungus SporesCan Heat Up Too Much
Steady Compost Activity When ColdAccessing It Requires Standing in the Sun

Pros

Faster Decomposition – Sunlight will increase the heat of the compost pile and cause rapid growth in the bacteria population. As the heat increases, different types of bacteria will thrive until, eventually, only thermophilic bacteria will be alive, and other microorganisms will be dead or dormant

Once the bacteria have eaten all the biodegradable material and consumed all the oxygen, their numbers die off, and the compost cools. If you compost in the sun, you can keep the temperatures up and constantly add more materials to feed the microbes allowing you to continuously dispose of kitchen scraps. 

KIlls Weed Seeds – Most seeds can not survive a hot compost and will be far less likely to germinate and cause problems in your garden the following spring. If you weeded too late and discarded tons of seed pods in your compost, make sure to let your bin sit in the sun, heat up, and cook those seeds. Once the seeds have heated up enough, the hulls will break down and become garden food like the rest of the organic matter. 

Kills Pathogens – These are the harmful microorganisms that make us sick. Usually, the time in the compost will kill off most bad bacteria, but for the really nasty viruses and parasites, getting that pile hot can help with peace of mind. Once your pile has heated up and sat for a few weeks, it will be safe to plant anything in but should be aged to 6 months before being used to top dress leafy greens. 

Kills Fungus Spores – Molds and fungi can survive in the soil and reinfect plants the following season. In most cases, it is advisable to either burn or dispose of diseased and fungal-infected plants away from your garden. In case a few accidentally made it into your compost, direct sunlight can raise the temperature high enough to sterilize the soil. Once you plant next year, the soil should be inert and not have any nasty spores to harm your plants.

Steady Compost Activity When Cold – When the winter cold comes, it can be hard to keep a compost pile active. The bacteria will naturally slow down, and you may be less likely to maintain a pile in the snow. If you place your compost in an area that gets direct sunlight in the cold months, you can help your microbes stay active and hungry. Make sure to have a good path to it so you won’t have to track through the snow every time you want to toss out some kitchen scraps.

Cons

Drys Out Quickly – A compost bin in the sun will dry out extremely fast. You will need to monitor moisture levels daily, or else your organic waste will stop decomposing. Without moisture, you will not be able to keep your microbes alive, and everything will become brittle and dead. You will not end up with a rich finished compost if you allow your material to constantly dry out.

Increases Food Smells – After the first day or two of leaving kitchen scraps in the hot sun, your compost may start to attract unwanted guests. Food in the heat smells much stronger than food breaking down at room temperature. If you will be composting in direct sunlight, make sure to seal your bin tight and brace it against bigger animals looking for a meal. 

Decreases Compost Nutrient Density – The more microbes that populate in your compost pile, the more nutrients from the organic materials they will eat. If you allow too much of the bacteria to feed and don’t control the inputs of the pile, you will end up with dirt and not compost. Hot temperatures and lots of dry materials can lead to underperforming soil additives for your garden. 

Can Heat Up Too Much – If your compost bin gets too hot, it will kill the beneficial microbes. The environment conducive to decomposition relies on the steady build-up and transition of different types of bacteria. If you kill them all due to excess heat, you will need to add more raw material and start the process over.

Accessing It Requires Standing in the Sun – When you need to fill up, turn, or maintain your compost, you will need to do it in the sun. Managing a compost in the shade is a pleasant experience full of nice earthy smells and a cool breeze. Adjusting a compost pile in the sun is sweaty, tiring, and 3 times as hard. Everything sticks to you when you get sweaty, and you feel exhausted afterward. 

Ideal Compost Bin Placements

Compost Bin

A compost bin can be placed anywhere, and that makes it a convenient composting method. But with the freedom to choose also comes the issue of which place is best to place a compost bin. There really is no best place for a compost bin, but different locations can help offset certain compost and climate limitations. 

If you live in a very hot climate composting in the shade can make it easier for you to manage your bin without getting overheated. You can also keep your bin at a stable temperature and will not have to maintain the moisture levels as carefully as you would a bin in the sun.

In a colder climate, you should make sure your bin has access to direct sunlight for the winter months to keep composting activity happening all year round. Placing your compost underneath a deciduous tree gives shade from the summer sun and heat in the winter and can be a good alternative placement in a temperate climate. 

Regardless of whether your compost bin is in the shade or sun, you will want to place it far enough away from your house so that you will not smell it. If you keep your bin clean and live in a snowy or rainy place, then keeping your compost accessible near paved walks and driveways can help you access it when the weather is bad. Make sure your bin is somewhere you can get to it and where you will use it to help reduce your home waste and build amazing soil.