Managing Composting Odours
Bacteria do not decompose complex sugars and cellulose straight to carbon dioxide, they break waste into smaller chemical compounds first. Many all these intermediate chemicals are 'volatile organic chemicals' (VOCs) and they have an odour.
The intermediate chemicals are very different when decomposition is via aerobic rather than anaerobic bacteria.
What is the BIO Filter made from?
The filter is a mixture of activated charcoal (to absorb cabbage odour (VOCs), zeolite (to absorb ammonia) and mature compost (to host bacteria that will consume VOCs and NH3 and prevent the filter overloading and ceasing to be effective.
What chemicals cause the putrid (anaerobic) odours?
The chemicals that produce the gut wrenching reaction are dimethly sulphide, dimethly disulphide(putrid), butyric acid (sour milk), valeic acid (vomit), fumic acid, acetic acid (vinegar), sulphur dioxide, hydrogen sulphide (rotten eggs). Anaerobic heaps also produce methane but this is odourless.
what do I do if my compost smells rotten?
If the compost in the HotBin starts to turn anaerobic, immediately stir in small pieces (not sheets) of corrugated cardboard (to absorb excess water) and wood chip bulking agent (to help re-aerate the heap).
Longer term, check the amount of bulking agent being added, check you are chopping waste small enough (<4 cm), and prevent any sheets materials (e.g. paper, biodegradable bags) getting into the bin.
The grass in my HOTBIN smells, why?
Large amounts of grass in a compost heap tend to produce a distinctive whiff of ammonia. This is created when excess nitrogen leaves the heap as ammonia gas. You'll notice this when composting large quantities of 1-2 day old grass. To prevent / remedy, mix in several hands full of shredded cardboard or paper.
For more advice visit 'How to compost grass'.
What chemicals cause the cabbage odour/smell?
The range of volatile organic chemicals (VOCs) includes alcohols, ketones, terpenes and aldehydes. These chemicals are "natural" and in low concentration form the basis of many plant fragrances, e.g. the sweet smell of pine/leylandi is a terpene, the orange fragrance is made up from a reputed 300 volatile chemicals. The HotBin bio-filter reduces most smells below noticeable levels.