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Publications archive - Waste and recycling

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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

On-farm Composting of Municipal and Commercial Organics as an Environmentally and Socially SustainableResource Recovery Scheme for Rural Communities

June 2003,
Environment Australia


5 Organics Collection

As mentioned already, residents in the Highfields trial area received a weekly waste collection service and dry recyclables were collected fortnightly. Waste was collected each Friday and recyclables every second Friday. Consequently, Friday was the ideal day for the organics collection as it would have been easily memorable for residents. It was envisaged to schedule the organics collection as a fortnightly service that alternated with the collection of dry recyclables. This would have resulted in a situation where all materials were collected on Fridays, waste on a weekly basis and dry and organic recyclables on an alternating, fortnightly basis.

However, this plan was not realised since the contractor was unable to provide the desired service. Instead, the additional organics collection service was scheduled for Tuesdays. Consequently, the kerbside collection of organics was scheduled for every second Tuesday, beginning on April 9th 2002. Considering the quoted pick-up costs, the project budget allowed for 17 collection rounds for all households in the Highfields trial area. Subsequently, Tuesday November 19th 2002 was determined as the last day on which organic materials would be collected within the Highfields Organics Recycling Project.

Quantities of organic materials collected during the eight month collection period are shown in Figure 24. Normally it is preferable to start an organics collection scheme in spring or early summer as that is the time when growth is most prolific and peak quantities of garden material are disposed of. However, this was not possible in the project's time frame. Consequently, collection quantities decreased during the winter period and fluctuated around 1,500kg per collection. Collection yields increased somewhat towards the end of the trial period in spring (September - November) but not as much as expected. The suppressed 'spring flush' of growth and collected material may have been due to intensifying drought conditions. Anyway, over the whole trial period, a total of 28,550kg organic material was collected, averaging 1,680kg per collection.

Quantities of organic materials collected in Highfields trial area

Figure 24 Quantities of organic materials collected in Highfields trial area

5.1 Collection and Presentation Rate

Quantities of collected organics materials were lower than expected. Data from Germany suggested that average annual collection yields of about 100kg per person (60-160kg/capita/year) could be expected in rural areas (Fricke et al., 1991). These figures represented climatic conditions in Germany. Growing conditions on the Darling Downs (South East Queensland) are more favourable than in Germany and biomass production per unit area of land is expected to be considerably higher. Consequently, it can be expected that the per capita production of green organics is substantially higher in Highfields than in rural areas in Germany. There is no doubt that, compared to normal circumstances, drought conditions during the trial period reduced plant growth and consequently also the amount of organics collected. The real potential of a dedicated organics collection in subtropical environs was demonstrated in Lismore, where each resident with an organics bin segregated approximately 120kg of kitchen and garden organics during 2001/02 (Lismore City Council, 2003). If self hauled material (private and commercial) is included, each resident with an organics kerbside collection service segregated approximately 173kg of organics.

On the other hand, residents were asked to use the organics recycling bin only for the disposal of garden organics that are 'not thicker than your small finger', i.e. have a maximum diameter of 2.5 cm. With regard to the total amount of garden organics being generated and removed from properties, it has to be remembered that large, unaccounted volumes were disposed of at landfill through self-haul by residents.

Despite these factors, the quantities of organics materials collected were lower than expected. This was primarily due to the low rate of bins that were presented for collection. During the first and second collection rounds 185 (58%) and 205 (64%) bins were put out for collection, respectively. The low presentation rate may have been due to an unfamiliar collection day (Tuesdays instead of Fridays) and the early start of the collection (6:00 am). The latter problem was addressed by delaying the start of the collection to 7:00 am.

Unfortunately, the collection vehicle used subsequently did not have a bin lift counter, which is why precise presentation rates are available only for the first two collection rounds. However, visual impressions conveyed by drivers indicated that the presentation rate never increased significantly. However, it appears that collection systems for dry recyclables suffered also from low presentation rates, which increased to today's level of about 80% only during the last few years (Nolan-ITU, 2001).

In order to identify reasons for the relatively low presentation rate, and to rectify them if possible, a mini survey among 22 households who participated in the trial was conducted in July 2002. Approximately two-thirds of households said that they put out their organics recycling bin for collection always or most times (Figure 25). The remainder either put their bin out sometimes (23%) or didn't use it (9%). These answers correspond well with the above described experience with collecting the organics bins.

More than two-thirds of survey respondents (68.2%) used the kitchen tidy bin to collect kitchen organics. Figure 26 shows that 63.6% of households used the organics collection system to recycle raw fruit and vegetables while only 27.3% disposed of cooked food in this way, and even less (22.7%) of fish and meat leftovers. The most popular garden materials disposed of in the organics recycling bin were tree prunings (59.1%), weeds and dead plants (59.1%) as well as leaves (45.5%).

Level of usage of organics recycling bin among participants four months after start of organics recycling trial

Figure 25 Level of usage of organics recycling bin among participants four months after start of organics recycling trial (Mini survey, July 2002)

Collection of various organic materials in the organics recycling bin among participating households

Figure 26 Collection of various organic materials in the organics recycling bin among participating households (Mini survey, July 2002)

Asked about problems they had experienced with the organics recycling scheme, 59.1% of surveyed households did not experience any problems while 40.9% did have some difficulties. Of those households that experienced problems, the following were most common:

Other problems encountered were odours from the organics collection bin and, associated with this, the claim that it was difficult to keep the bin clean.

Problems experienced by householders with the organics recycling project during the first four months of the trial

Nb: These figures do not amount to 100% because respondents selected more than one option
Figure 27 Problems experienced by householders with the organics recycling project during the first four months of the trial (Mini survey, July 2002)

Unfortunately, the survey revealed very little as to why the presentation rate was low. Survey results did not support the assumption that a high proportion of residents that experienced problems no longer used the bin or only sporadically (see Figure 27). The problems experienced by residents also left relatively little room for remedial action other than to reiterate the advice to wrap kitchen scraps in newspaper in order to reduce the likelihood of odour and fly problems.

5.2 Quality of Collected Organic Materials

It is undisputed that the intensity with which the public education campaign is conducted has a direct influence on the level of impurities in the collected organic materials. However, no matter how good a public education and motivation campaign might be, it is not possible to collect organic materials from the kerbside that are 100% free of undesirable components such as glass, plastic and metal. Overall, the quality of organic material collected in Highfields was very good, as it showed very low levels of impurities. An audit of the kerbside collected organic material showed that impurity levels amounted to only 0.3% (Figure ). According to experience in Germany (Fricke et al., 1991), average impurity levels in kerbside collected organics are considerably lower in rural/regional areas (1.77%) than in cities (2.24%) and city centres (4.02%). Impurity levels in rural/ regional areas ranged between 0.2% and 4.0%. This was confirmed by Gronauer et al. (1997) who reported somewhat higher figures (1% - 6%) for rural areas on the outskirts of Munich. Interestingly, their study found that impurities were significantly lower where decentralised on-farm composting was used rather than large-scale centralised composting operations. Organic material collected in the district that had embraced an on-farm composting concept contained 1% to 2% impurities for towns and rural areas, while organics from two districts with centralised composting showed impurity levels between 2% and 6% for rural areas and between 4% and 10% in regional centres.

This demonstrates that, by any standard, the organics material collected in Highfields was very clean. However, understandably the farmer thought that even the relatively few impurities found in the material were too much. His staff had to pick them out and they had the potential of ending up on his land.

Composition of kerbside collected organics

Figure 28 Composition of kerbside collected organics (average of two audits in October and November 2002)

The audit of the organic materials collected in October and November showed that lawn clippings comprised 42% of the total mass (Figure 28). This figure seems high and not necessarily representative of the entire collection period. Paper also seems somewhat over represented at 6%. For most of the collection period, lawn clippings were not as prominent as Figure suggests, compostable garden organics comprised the majority of material delivered to the farm.

Schematic layout of on-farm composting area

Figure 29 Schematic layout of on-farm composting area