About six years ago I decided to try composting. Since then I’ve made pretty much every mistake in the book. I’ve had the pile that stank so badly the neighbours complained. The heap that sat for two years without breaking down. The bin that attracted every rat in Manchester. The batch of compost that was full of weed seeds and turned my garden into a bindweed jungle.
The frustrating thing about compost problems is they seldom just smell bad. An efficiently managed pile will turn kitchen waste into sweet smelling, black garden soil improver within 4-8 months. Badly managed piles are breeding grounds for rats and flies, sources of terrible smells, or just sit there year after year without changing. Good composting technique means understanding what’s happening in your pile and how to fix it when things go wrong.
Troubleshooting Compost Problems
Most compost guides talk about how composting works in theory. Carbon to nitrogen ratios, ideal moisture levels, proper aeration techniques. All well and good, but when your compost bin starts attracting rats or smelling like vomit you want practical advice. What does problem X look like, what causes it, and how do you fix it? This guide will walk through common compost problems, why they occur and how to fix them.
What’s Wrong With My Compost?
The Science Behind Compost Problems
Most compost troubleshooting is done using trial and error because people don’t know how composting works under ideal conditions. Learning how to fix common compost problems requires understanding compost science.
Think of successful composting as controlled decomposition. Specific types of microorganisms break down your kitchen scraps into good compost. These microbes require very specific conditions to thrive though.
**Aerobic vs Anaerobic Decomposition: ** Good compost happens when aerobic microbes devour your garbage. As long as they have plenty of oxygen to breathe they produce carbon dioxide, water vapour and release heat. When oxygen runs out anaerobic bacteria take over. These guys work slower and give off hydrogen sulphide, ammonia and organic acids. The bad smells (source).
**Temperature Phases of Composting: ** An actively working compost heats up as billions of microbes reproduce. Initially temperatures will rise to about 40°C during what’s called the mesophilic phase. This phase is dominated by bacteria and fungi eating sugars and proteins. Thermophilic phase occurs when temperatures reach 60-70°C. This high temperature is key because it kills weeds seeds and parasites. The EPA has a standard of maintaining 55°C for three days for aerated static piles for pathogen kill off (source). Without enough oxygen your pile never reaches thermophilic temperatures.
**Moisture Problems: ** Water is required for microbial activity but too much water squeezes out oxygen. Ideally your compost should be about 40% to 60% water(source). Another way to think of it is the compost should feel like a wrung out sponge (source). Below 40% water microbial activity greatly diminishes. Above 60% your pile is too wet and anaerobic conditions occur.
**Carbon To Nitrogen Imbalances: ** Carbon provides microbes with energy, nitrogen is used to build proteins. Add too much nitrogen and your pile will smell like ammonia. A strong ammonia smell actually indicates your carbon to nitrogen ratio is too low(source). Add too much carbon and decomposition slows because microbes don’t have enough nitrogen to reproduce.
Diagnose Common Smell Problems
When your compost starts to smell that’s often the first sign something has gone wrong. Different problems create different smells. By identifying the smell your compost pile is producing you can pinpoint the exact problem.
**Rotten Eggs: ** This stench is created by hydrogen sulphide gas produced by anaerobic bacteria. The pile is either too wet, too compacted, or both. The solution is turning for aeration and adding carbon to soak up excess moisture. Mix in dry brown carbon materials like shredded paper cardboard or dry leaves. If the pile is extremely wet you may need to remove some of the wet materials and mix them with browns before reincorporating them into the pile.
**Ammonia Smell: ** Sharp pungent ammonia smells indicate too much nitrogen compared to carbon. Most likely you added too many grass clippings or kitchen scraps without mixing in browns. Problem smells usually come from too much nitrogen rich “green” material or not enough carbon rich “brown” material (source). Another possible reason is excess water. Add brown materials as soon as you notice this smell. Dry leaves shredded cardboard or paper will help.
**Sweet Alcohol Smell: ** When compost smells like fermentation instead of composting you need to fix two problems: excess moisture and lack of turning. Too much fruit and other sugary wastes cause this problem when piled anaerobically. Solution is the same as rotting eggs.
**Putrid/Rotting Meat Smell: ** Unless you added meat to your compost pile this smell is caused by anaerobic hot spots of fresh kitchen waste. Avoid letting pets (including cats) excavate your pile! Fresh grass clippings and kitchen waste release a lot of moisture. Don’t dump fresh “greens” all on top of browns. Mix them in or layer accordingly.
Rule of thumb with smell problems: if it smells bad it’s anaerobic. Solution is always to increase oxygen. Turn the pile, fluff it up, and add carbon to absorb excess moisture.
Identify Visual Compost Problems
Besides smelling your compost you can usually tell something’s wrong by simply looking at it.
**White Fuzzy Stuff: ** If you see white fungal growth on top of your pile that’s usually ok and often a good thing. White fungi decompose tough woody stems. However if you see thick white layers that penetrate deep into the pile and it feels slimy that’s bad. Pile is too wet and lacking oxygen. Turn and add browns.
Slimy Layers on Pile: If you pull back the top layer and find thick slimy layers of grass clippings or leaves stuck together you’ve got anaerobic conditions. This is caused by layering your ingredients too thick without turning or adding too many greens that get soaked with rainwater. Take the slimy layers and mix it with browns then turn frequently.
Not Changing: When the material in your compost bin look the same after several months chances are decomposition has stalled. Too dry? Check moisture levels. If pile is dusty dry add water while turning. Too little nitrogen? Once moisture levels are OK add some fresh grass clippings or kitchen scraps.
Flies, Rats, & Pests: Seeing flies around your fresh additions is normal. However, if you see large populations of tiny black flies your pile is too wet on the surface. Cover all fresh additions with browns and don’t leave kitchen scraps exposed. Rats and mice means accessible food. Don’t add cooked food meat or dairy. Cover fresh additions with plenty of browns.
Help! My compost won’t heat up
Temperature is another easy way to tell if your compost is working. If your pile is completely cool there are several possible problems.
Too Small: Small piles don’t insulate well. Covered compost piles allow for higher temperatures by trapping heat near centre of mass (source). Your pile should be at least one cubic metre ideally. If you don’t have room for a large compost pile focus on insulating your pile by covering it or using an enclosed bin system.
Inactive Microbes: Conditions are dry enough and you have plenty of greens and browns but the pile just won’t heat up. Active microbial populations are required to start decomposition. Add a shovel full of finished compost garden soil or store bought compost activator. Animal manures also contain microbes and will add nitrogen as well.
Too much Carbon: If your pile is made up mostly of dried leaves paper and other carbon rich materials it will decompose slowly. Add some nitrogen rich food waste grass clippings or sewage sludge. Too much nitrogen can also create ammonia which actually suppresses microbial activity.
Too Cold: Decomposition happens extremely slowly in cool temperatures. Winter piles may show very little activity until spring. This isn’t a problem and isn’t caused by poor management.
9 Common Compost Management Mistakes (& How to Fix Them)
Knowing what you’re looking for when it comes to compost problems is half the battle. But how do you avoid these problems in the first place? Here are 9 common compost mistakes.
Mistake #1: Adding too much at once. Don’t add your whole lawn clipping or put that entire bag of leaves on top of your pile. These big heaps of greens mat down and compact creating anaerobic pockets. Add your ingredients in layers, mixing each new addition with the existing pile.
A good rule of thumb is never add more than a 5cm layer of greens without mixing them with browns.
Mistake #2: Putting kitchen waste on the pile any old way. This one is the biggest problem for beginners. Adding kitchen waste every time you clean up without balancing carbon mixing or covering encourages flies maggots and odours. Cover each addition of kitchen waste with brown materials. If you can’t be bothered mixing greens and browns daily start a small kitchen bin and add the week’s food waste at once.
Mistake #3: Never turning. There are guides out there that say you can make compost without ever turning your pile. This might be true if you add perfectly balanced ingredients in precisely correct amounts… every single time. For the rest of us regular turning makes composting much easier. Most advice says to turn every 1 to 2 weeks (source). However if you want to minimise odours and really boost oxygen levels turn every 3-4 days (source).
Mistake #4: Adding the wrong stuff. Animal products meat dairy and yes even eggs can create odor problems if you’re not careful. Cooked food will draw vermin and does not compost well. Try to stick to grass clippings weeds leaves fruit and veggie scraps. No food that has gone bad unless you want to introduce plant disease into the mix. Weeds with seeds or perennial weeds take far longer to break down.ide greens.
Mistake #5: Thinking you can rush it. Impatient people tend to overwater their compost pile, over turn the pile and add compost accelerators they shouldn’t. Good compost takes time. Even well maintained piles can take three to six months. Don’t interfere unless your troubleshooting a problem.
troubleshooting article
| Season | Mistake | Why? |
|---|---|---|
| Summer | Mistake #6: Adding too few greens. | When composting in warm months your pile may dry out before it breaks down. Too much carbon accelerates drying. Don’t be afraid to add plenty of greens during summer. |
| Winter | Mistake #7: Adding too many greens. | It’s the opposite in winter. Cold piles take forever to break down. Adding too many nitrogen rich greens will create odor problems while decomposition is slowed. |
| All Year | Mistake #8: Not keeping records. | When you run into problems not being able to remember what you last added makes troubleshooting near impossible. Keep track of your compost additions in a notebook. |
| Varies | Mistake #9: Not adjusting for your climate. | As stated above different seasons require different management. But what if you live where it’s wet year round? Or hot? Or windy? What about cold and dry? Composting in each of these situations requires tweaks to the basic method. |
Benefits Of Proper Compost Management
Not sure you want to put in the effort? Here are some of the benefits to troubleshooting your compost pile instead of starting fresh.
Any composter can list the benefit of saving waste from the landfill. But did you know well managed compost actually decomposes 3-4x faster than neglected piles? If you’re tossing food waste in your compost and walking away you could cut your turnaround time in half by simply balancing your ingredients, watering, and turning.
Better quality end product. Properly made compost has superior structure. Nutrient balance and biology than compost that’s had raw kitchen scraps sitting in it for years.
Avoid odour problems. Nobody likes a smelly compost bin. Learn how to manage yours properly and you won’t have to hold your breath while spreading compost anymore.
Pest proof your pile. Flies are normal but large populations of flies are a sign of management problems. Fewer flies and no rats means you don’t have to worry about pests at your compost beckoning.
Compost year round. Once you learn the basics of troubleshooting you can adjust your methods to match the season. Stop worrying about winter composting or jumping through hoops to keep your pile active in summer.
Know what goes into your compost. All those problems I had earlier? They came from adding the wrong things. Meat dairy cooked food will draw rodents and pests. Certain weeds can take years to break down and others bring disease. Know what’s in your compost before you use it in the garden.
Get it Back On Track
I know that was a lot of information. Here’s a quick guide to get your compost healthy again.
Week 1: Take everything that’s obviously wrong with the pile and toss it (yes I mean toss it in the trash). Grab a handful of compost and squeeze. Does it feel like a wrung out sponge? Sniff your compost. Do different areas smell differently? What do you see? Green grass clippings? Dead leaves? Almost finished compost?
Weeks 1-2: Take immediate action to correct the problems you observed. If pile is too wet and smelly turn it,add lots of browns and mix in dry leaves shredded paper or cardboard. Too dry and not heating up? Turn while adding water and some green grass clippings or kitchen waste. Pest problems? Remove any traces of food that went bad. Cover all your kitchen waste with browns and try burying it.
Weeks 2 On: Set up a turning schedule. Get some storage for your brown materials so they’re ready to go when you need them. Kitchen waste shouldn’t just go on the pile whenever you happen to remember. Get a container to collect waste then add it all at once once a week. Once you have a regular schedule you can slowly start monitoring compost moisture levels and temperature.
Tools You’ll Need To Get Your Compost Back On Track
| Tool | Cost (£) | Notes |
|---|---|---|
| Garden fork (For turning) | £15-35 | One time purchase |
| Watering can or hose | £8-25 | If you don’t already have one |
| Brown materials | £0-10 | Hopefully you have plenty of these laying around. Cardboard newspaper and dry leaves are free. |
| Cover / tarpaulin | £10-20 | If you live somewhere rainy or want to protect your pile from excess sun |
| Storage containers | £5-15 | To store kitchen waste until collection day and brown until you need them. |
Total Cost: £38-£105 NOTE: These are average UK prices. Costs will vary from country to country.
Once youve fixed your compost mistakes won’t happen again!
Well that’s it. Like I said at the start I made (and solved!) every problem compost newbie can make. I don’t care if you’ve had your pile for a week or wasted years worth of materials. If you follow this guide you’ll have finished compost in no time. Once you understand how to troubleshoot compost problems they won’t recur.
Oh, and one last thing. I make every effort to link only to credible sources when quoting facts. If you notice improperly sourced information or any inaccuracies at all please let me know in the comments.
