Organic materials that are normally considered waste can be processed into a variety of products, many of which are used to improve the fertility of soils.
Organic materials can be processed into soil amendments (such as compost or mulch) using mechanical and/or biological methods. Composting, anaerobic digestion and worm farming (vermiculture) are some of the better know methods for processing organic wastes.
The types of organic wastes which can be processed into soil amendments include:
- green waste from the maintenance of parks and gardens, land clearing and forestry activities
- the biodegradable organic fraction within solid waste from households
- biosolids from the secondary treatment of sewage sludge
- waste wood from timber production and the manufacture of timber products
- agricultural and horticultural wastes, such as manures, dairy waste and spoilt produce
- organic wastes from commercial activities such as food processing and retailing food products.
Importantly, the biodegradable fraction within solid waste can be recovered and consequently contribute to increased resource recovery in Western Australia. These biodegradable materials (which include food waste, green waste, paper, cardboard, animal waste and textiles from natural fibres) constitute over 50% of municipal solid waste from households.
Across Western Australia over 580,000 tonnes of organic material was collected for recycling during 2011/12, with green waste and recovered material from the biodegradable fraction in solid waste contributing over 70% of recovered organic materials in annual industry surveys.
The Authority encourages community participation in the resource recovery of organics and has provided a series of fact sheets to support active community involvement, from being part of a community group to composting garden waste and food scraps at home.
(For further information see our community organics section here)
When organic wastes are adequately processed into soil amendments to meet the requirements of specific land application situations, those processed materials become fit-for-purpose products.
For instance, mushroom growers often utilise incomplete composts made from straw and manure, while some horticultural applications will prefer products with higher nutrient levels, as these can offset inorganic fertiliser use. In land rehabilitation applications, a course composted mulch may be preferred to help reduce water use and soil erosion.
In many instances horticulturalists, parks and garden staff or land managers will prefer composted products that have been stored over time to mature so the material is more stable and poses less risk to young plants and seedlings.
In each case information about the characteristics and quality of a product helps to make informed choices about which is suitable.
The Authority actively supports the promotion and wise use of organic resources that would otherwise be considered waste. When properly processed, recycled organic material applied to land can improve soil quality, increase water use efficiency and reduce nutrient losses. In 2009 the Waste Authority released a position statement on recycled organics.
The Authority considers appropriately selected and treated organic waste should be recycled wherever possible and used to replenish soil organic matter. Separation at source is the preferred strategy for recovering organic waste, particularly garden organics. Compost derived from source-separated organic wastes and single-waste sources is more likely to meet quality requirements for unrestricted use, while products derived from source-separated waste can find use in many soil amendment applications.
In 2012, a Food and Garden Organics Best Practice Collection Manual was prepared by Hyder Consulting for the Australian Government Department of Sustainability, Environment, Water, Population and Communities. The manual received a significant amount of input from a variety of stakeholders, including councils currently operating food waste and green waste collection systems, and may be of use to other organisations investigating doing the same.
While source separation of organic waste is the preferred strategy, there is also a substantial need for different quality composts and other soil amendments in a range of important applications. These products can be derived from a number of sources, including the biodegradable fraction within mixed solid waste, which has been extracted through mechanical separation and stabilised through biological treatment to produce various soil amendments.
To determine the quality of a product derived from organic waste, it should be tested and certified through a recognised product quality assurance system, such as the Australian Standard AS4454 for composts, soil conditioners and mulches.
This organisation provides a wealth of free information on organics recovery
Source separation – or separating waste at home, in the office, on building sites and in public places – has been shown to be effective in increasing recycling. More importantly, good source separation reduces contamination, which in turn improves the quality of the recycled product.
Fertiliser runoff is a major problem for our waterways. This guide has been prepared to assist you with reducing these impacts.
A report on the trial of applying compost in the establishment of the Anstey Wetland on the Forrest Highway. Produced by GHD for the Department of Environment and Conservation
An episode of Gardening Australia (Series 24, episode 5) covering waste issues and how better management of organic waste can help our environment