Roof, Balcony and Patio Gardening
Most advice on composting is designed for those with conventional gardens but those with balconies, patio or courtyard gardens and roof gardens can also compost
The type of composter will be dependent on whether it is intended to compost only garden and uncooked vegetable kitchen waste or whether cooked foods/meats are to be included.
Garden and uncooked Kitchen waste
While the majority of compost bins are designed to be placed directly on soil, allowing worms and other soil creatures easy access and permitting leachate to drain way, there are significant groups of composters that are mounted off the ground or are designed to be placed on a solid base. In addition, there are systems, such as wormeries with different models available for outside and for indoor use.
In a patio garden a “conventional” compost bin should be positioned, if practicable in a sunny part of the garden on bare soil but if this is not possible in a slabbed or courtyard garden a few slabs could be removed to create a space for the bin allowing direct access to soil. If lifting slabs or pavers is not practicable, the bin can be located directly on concrete, tarmac, patio slabs or decking. However, it is normal for liquid (leach ate) to seep out of a compost bin and this may stain surface.
One way of avoiding this on patios, balconies and roof gardens a small raised bed may be created to house the bin to reduce the likelihood of staining the surface. The slaps or decking within the raised bed where the bin is to be placed should be covered by at least three inches of coarse gravel or stones. This is covered with a geotextile membrane, fabric landscape liner, degradable plastic or coir, followed by the soil layer. Once compost has been produced, it can be used to increase the level of organic matter in the raised bed soil to absorb excess moisture so to reduce seepage. Compost worms, and other beneficial composting creatures, can be introduced by the addition of inmature compost from garden bins or fresh manure to both the bin and the raised bed. It is advisable to monitor the condition of the bin and make further additions when required. One of the advantages of mounting the bin on a raised bed is that the compost in the bed will form a reservoir for the compost creatures.
Conventional Compost bins
The choice of bin will be dependent on the space available, the amount of waste to be composted and whether the waste includes cooked food.
I personally favour plastic bins, with a base for patio, balcony and roof top composting. Although wooded New Zealand bins have been used successfully on larger rooftops gardens where only garden and uncooked kitchen waste is being composted. The provision of a base to a plastic bin helps to reduce leachate seepage also assists in reducing distortion of the bin during use. In addition, a base reduces the risk of the bin to being relocated by the wind as both the bin and contents would need to be blown away rather than just the plastic bin. Bases are available for a wide range of plastic bins including the low cost bins subsidised by the local councils
Small Tumbler bins
There is an increasing range of tumbler style compost bins available and as these are mounted on a stand, they are suitable use on any solid surface such as a courtyard, patio or rooftop. A compost tumbler will normally be more expensive than an entry-level conventional bin and require regular turning to aerate the material.
If these are to be used on a rooftop, or other windy location, consideration should be given to fixing the stand to the slabs as an additional precaution. A tombola style horizontal bin is probably more practical, and wind resistant, than the larger barrel shaped ones although smaller models such as the Draper 180 litre barrel frame tumbler are compact and this model is turned by use of a handle. If a tumbler that is spun by hand is preferred, the Henchman single 190litre model is made in a more rounded shape, which should make turning a full bin easier than is the case with some of the barrel, shaped models.
Mantis make a 140litre “Back Porch” compost tumbler advertised as being suitable for city properties and very small gardens and this would also be suitable for a rooftop or courtyard garden. This composter has two wheels so that it can be easily moved, a useful feature where space is limited. A similar but larger 190 litre Heavy Duty Garden Tumbling composter by Selections is also available. Larger tumbler bins could also be used depending on space. See the page Tumbler Composters for information on more of the bins that are avilable.
Commercially available domestic wormeries provide an effective means of converting kitchen waste into compost and a liquid feed (worm wee) and will normally have feet raising it above the ground so the worm wee can be drained making it ideal for use on a hard surface.
Such wormeries are not normally used for cooked food waste as it may smell and attract flies (burying the waste in the compost reduces the likelihood of smell). The compost produced in a wormery is ideal for growing plants in containers and the worm wee provides a constant source of liquid feed.
The choices are as set out in more detail in the wormery section Wormeries
There are compost bins and techniques suitable for cooked food as the main source either of compostable material or as part of a mix including garden waste.
The smaller bins included bins in the section on Food Compost Composting Food would be suitable for mounting on hard surfaces The Green Johanna, which is best mounted in a shady spot, and Hotbin, suitable for locating in sun or shade, are good bins that will compost both garden and kitchen waste including cooked food. An empty Hotbin is quite light and it is recommended that it be placed in a shelter position or secured so that it is not blown over, or off the roof, in strong winds
The Jorra tumbler will deal with cooked food waste from a large family. If larger quantities of cooked food is being produced one of the larger tumbles in the Jorra range or a Ridan composter are recommended.
Bokashi bin system.
A bokashi bin is ideal if you are already doing traditional composting using a conventional bin for composting garden waste and uncooked food but want to convert small quantities of cooked food into a form that can be added to a conventional compost bin. Alternatively, the cooked food can be fermented in the Bokashi bin and resultant material buried in any part of the garden that is available. more details are given on Bokashi bins