Hot Composting Apples
As it is becoming customary to celebrate Apple Days across the country including the pressing of apples to make juice I felt it might be useful to expand the advice on composting apples.
Under normal circumstance apples can be added to the composting as and when they are no longer suitable for eating and this includes the occasional windfall during the summer months. Chopping the apples will of course speed the composting process. However in the autumn larger numbers become available together with the mushy pulp resulting from juice extraction a slightly different approach is needed to deal with the sudden influx of “greens” into the bin or heap. If creating compost heap or using a New Zealand bin the minimum size recommended is 3cu feet. Smaller heaps will breakdown more slowly and will need more frequent turning to keep the composting process working.
Where there are a lot of apples it is best to layer them with browns and continue making alternate layers of apples and browns until all the windfalls have been used. If you only have a few trees it might be better to collect the apples in some kind of storage container i.e. a bucket or bin so that you have enough to make several layers about 4” thick at the same time. If possible other greens should be added at the same time as the chopped or pulped apples to introduce air spaces and variation into the green mix.
Creating the correct green brown ration is important so as to prevent the apples fermenting and producing an unpleasant smell. One part green to two part brown material is recommended but if the fruit is going to form a high proportion of the compost heap the addition of a bulking agent to absorb the liquid and provide plenty of free air spaces (FAS) to maintain aerobic decompostition is recommended. For more details on bulking agents please see the page on Food Composting.
Although autumn leaves are normally used to make leaf mould they do make an excellent component of the brown layer. Sawdust from a vegetarian pet, such or chicken can also be added. I also add shredded computer paper. A shovelful of finished compost from an adjacent bin, plain garden soil or manure can be added to kick start the microbial activity that will turn the apple waste into quality compost. As with most hot composting systems water the bin or the browns at the start of the process and at any time that it looks dry. Turn the compost mix to aerate it and cover with browns (I use the shredded paper) as this will reduce any smells from the bin and reduce numbers of fruit flies when the lid is removed or heap uncovered
For the first week the material should be turned daily to aerate the material ensuring that microbial activity heats the content. When turning move the material on the outside of the pile toward the center. This can be reduced as the effect decreases. See the section on hot composting if you have a thermometer monitoring the temperature it can provide additional interest (especially for children).
Do continue to check the compost condition of the bin weekly. If it becomes to dry it will stop working while if too wet anaerobic bugs will take over and the temperature will fall and the smell will increase. If dry add water a little at a time, if wet add more browns e.g. dry leaves. After two or three months the compost should be finished dark brown in colour with an earthy smell and no apples identifiable.
Cold Composting Apples
If you have fewer apples and intend to add them to a bin already in use a simplified techniques can be used, If the apples are whole chop the apples with a spade and add to the bin to make a layer two or three deep. Cover this with a wet leaves, bedding from vegetarian pets, rough compost or old straw. Repeat the process adding apple and brown layers until the apples have been used. Finish with a layer of browns to reduce odours and insect pests. Using this cold composting process it may take up to two years to produce good quality compost
I have more windfall plums than any other fruit in the garden. The flesh of Plums will compost quite quickly but the stones will take much, much a longer. They will compost eventually, after a few years but if, you intend to harvest your compost normally after a few months they will still be there. The compost will need screening/sieving to remove them
The same applies to other fruits such as apricots, avocados mangos. nectarines, peaches, and even cherries although the stones are much smaller.
The stones from the larger fruit such as plums could be removed before composting or if your time is limited you could soak the seeds in water(hot water is best) this is said to speed up the decomposition process a little.
Composting Apple Pulp
Food waste has a high moisture content and as it is broken down water is released into the composting vessel and as a result the structure of the composting material will not contain sufficient air spaces for aerobic composting and the food will decomposes into a wet, smelly sludge. This can be avoided by the use of a bulking agent to add structure (or bulk) to the compost and create air spaces allowing air to circulate within the composting material. A good bulking agent will also absorb the liquid from the food to maintain the correct moisture content of the food waste during composting. In the case of fruit pulp, the need for an effective bulking agent is even more important as we are starting with a wet mushy sludge that will not compost aerobically without the addition of a bulking agent to provide carbon and an open structure. I would recommend mixing sawdust with the pulp to absorb most of the liquid before adding an additional bulking agent such as woodchip to provide air spaces allowing the composting bacteria to work aerobically. If possible, mix the pulp and bulking agent before adding to the compost bin to ensure a through mix. The addition of shredded paper or corrugated cardboard may also be beneficial
I have included more detail on the use of bulking agents when composting food in the page on food composting.