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Hot Composting

Hot Composting is an alternative to cold composting.

Unlike cold composting, the term "hot composting" refers to a method in which microbial activity within the compost pile is optimised by harnessing the heat it creates naturally, resulting in finished compost in a much shorter period of time.

Temperatures in a hot compost heap range between 49-77 degrees C. Microbial action breaks down the deposits and the heat kills pathogens. The optimum is to keep it above 40 and below 65 degrees C, otherwise the microbes themselves start dying off. New additions are mixed in and every few months the bottom of the unit is opened and the bottom layer of finished compost is removed.

Food Scraps, garden cuttings, and animal manure (including human) can be composted in a hot composter. Composting needs additional carbon, so sawdust, straw, hay, or dry grass work well. It's all about balance. Dog/cat droppings theoretically can be added, however they have more potential pathogens than human manure and thus require hotter and longer composting.

The manufacturers of the Biolan hot composting units state six weeks to create topsoil for ornamental plants but probably aiming for 3 - 6 months realistically, or 12 months for use on edible crops. A hot composting unit is insulated meaning it should still be able to keep processing over the winter but may be a bit slower than the summer.

The high temperatures in a hot compost heap kills the pathogens in the human manure as well as in food scraps and destroys seeds of weeds in garden matter. The unit is insulated to help keep the heat in all year round and keep the temperature high. Gloves and basic hand hygiene would need to be considered when working with the unit and stirring contents. The unit is sealed, discreet and covered.

If the composting process is happening correctly and the unit is sealed then there should be no odour. A smell can indicate that there isn't enough oxygen in the unit, that the compost is too dense or wet. When this happens anaerobic bacteria become active, they produce a gas that we can smell. More cover/bulking material can be added to dry out the contents, to restart the aerobic bacterial activity. This will usually deal with any smell.

The unit would need the new contents stirring in roughly once a week with monitoring of the temperature every few days to check it wasn't too hot or cold or the mixture too wet.

The hotbin should be added to several times a week all year round. This should be manageable with a handful of regular users adding food scraps every few days and toilet contents every few weeks.

Last Edited: 09 May 2024

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