Most problems that show up in a tropical or humid compost heap trace back to one of two forces: too much water, or too much soft green nitrogen with not enough dry carbon to balance it. Recognising which one you're looking at, and sometimes both at once, is most of the battle.
Diagnosing the Problem
Waterlogged and anaerobic
The single most common tropical-specific failure. A heap that smells sharp, sour or like rotten eggs, feels sodden right through and has gone dark and sludgy has almost certainly been waterlogged by rain that couldn't drain away. Fix it by improving drainage and roofing (see Chapter 2 and Chapter 3), turning the heap thoroughly to reintroduce air, and mixing in extra dry carbon material to soak up the excess moisture.
Slimy and smelly, but not fully waterlogged
A heap can turn slimy and unpleasant without ever having been drenched. This is usually too much nitrogen-rich fresh green material and not enough dry carbon, an easy imbalance to fall into here given how abundant greens naturally are. Rebalance it following the carbon-and-nitrogen guidance in Chapter 4, working in extra dry material until the texture loosens up.
Mould or fungal growth on the surface
Visible mould on the surface is common in humid conditions and is more of a visual and textural concern than a genuine problem in most cases. It generally resolves once the heap is turned and gets better airflow, though heavily mouldy material shouldn't be handled carelessly.
Ants, cockroaches and flies
Warm, humid conditions draw these pests readily, particularly when food waste is exposed on the surface rather than buried in the heap. Bury fresh scraps under existing material rather than leaving them on top, and keep meat and dairy out entirely (see Chapter 5).
Running hot and drying out in patches
A large, dense, fast-heating heap can dry out in localised patches even in a generally humid climate, distinct from the whole-heap drying problem an arid climate faces. Turn the heap and check that moisture isn't being driven off from the hot core, topping up with water if the dry patches are widespread.
Frequently Asked Questions
My heap has gone slimy and smelly, what's wrong?
This is usually one of two things, and often both together. The heap may be waterlogged, with rain having filled the air pockets aerobic bacteria need, or it may simply have too much nitrogen-rich fresh green material and not enough dry carbon, which is an easy imbalance to fall into given how abundant greens are in this climate. Turn the heap to reintroduce air, improve drainage and roofing if water is the cause, and mix in more dry carbon material either way.
Is mould on the surface of my compost heap a problem?
Usually not. Mould and fungal growth on the surface are common in humid conditions and are more of a visual and textural concern than a real problem in most cases. It generally clears up once the heap is turned and gets better airflow. Heavily mouldy material is still worth handling with a little care, such as wearing gloves and avoiding breathing in disturbed dust.
Ants, cockroaches and flies keep turning up around my heap, why?
Warm, humid conditions draw these pests to a heap readily, particularly when fresh food waste is left exposed on the surface rather than buried within it. Always bury fresh scraps under existing material rather than leaving them sitting on top, and never include meat or dairy, which attracts pests far more strongly than plant waste does.