Department of the Environment

About us | Contact us | Publications

Settlements Header ImageSettlements Header ImageSettlements Header Image

Publications archive - Waste and recycling

Disclaimer

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Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time.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


12 Collection of Organic Materials in Biodegradable Bags

12.1 Background

Collection costs in Crows Nest Shire include the provision and maintenance of receptacles for waste and recyclables. However, this is not necessarily the case in other local authorities. In those cases either council owns the bins or residents have to purchase their own bin.

Local authorities are often reluctant to introduce or expand kerbside recycling services if it involves the purchase of wheelie bins. The acquisition of bins can represent major capital expenditure and strain budgets, particularly in smaller councils.

However, materials collected from the kerbside do not necessarily have to be placed in bins. Collection of recyclables in crates is used in many Australian communities and the use of bags to collect waste is widespread in the UK and the USA (Biala, 2001). Neither crate nor bag collection systems utilise side-loading vehicles, which are commonly used in Australia; they usually rely on manual pick up and transfer into the collection vehicle. According to Biala (2001) it is expected that existing bag collection systems in the UK will be phased out due to workplace health and safety concerns and that the introduction of such manual systems would not be acceptable in Australia for identical reasons.

The above outlined situation created a need to assess the possibility of using a side-loading vehicle to collect bagged waste or recycling material from the kerbside. Since this investigation took place within the framework of the presented project, the trial assessed the use of bags for the collection of garden organics. This provided the added opportunity to test the suitability and strength of biodegradable bags for this purpose.

12.2 Trial

Side loading vehicles utilise either a 'comb lift' system or a 'grab lift' system. Only grab lift systems can be used to pick-up bags. Since all vehicles used in Crows Nest were equipped with comb lift systems, cooperation with Brisbane City Council and its contractor, SITA Environmental Solutions was sought to conduct the envisaged trial.

The trial was conducted at Nudgee transfer station in August 2002 and utilised one of Brisbane City Council's brand new waste collection vehicles with a grab lift system (see Schmidt, 2002). Valpak (Aust) Pty Ltd provided sturdy compostable bags (thickness 75Ám) with a capacity of 70L. Using stockpiled garden organics, 40 bags were filled with different types of garden residues, including grass clippings, leaves, tree and brush cuttings, pole-type tree prunings and logs. Roughly equal numbers of bags were filled with (i) predominantly fine garden material, (ii) predominantly coarse garden material, and (iii) mixed garden material (fine and coarse). Bags were randomly closed with string or by tying together the top ends of a bag, or they were left open where bags contained long branches. Full bags either stood upright or lay on the ground. The filled bags were lined up in two rows for pick-up by the waste collection vehicle (see Figure ).

12.3 Results

Figure on the following page provides several visual impressions of the pick-up trial.

The trial aimed at assessing (i) the ability of side-loading vehicles with grab lift arms to pick up garden organics in bags and (ii) the usefulness and strength of compostable bags. Unfortunately, results did not prove successful in every respect.

Some difficulties were experienced in filling the bags, particularly with entangled, spindly and thorny materials. This was due to the fact that floppy bags can be difficult to fill with rigid and bulky material. However, the bags proved very strong and sturdy. The compostable bags did not split open when picked up in a 'tweezer-like' fashion (see below and most did not tear when flung to the top of the vehicle.

On the other hand, picking up the bags and dropping them into the vehicle with an existing grab lift proved unsuccessful. The following problems were observed:

  1. It was not possible to pick up any of the bags that lay flat on the ground. Many of the upright bags were not tall enough to be picked up by the loading arm. The loading arm could not be lowered sufficiently to enable pick-up of bags.
  2. The grab of the loading arm did not close sufficiently tight to enable pick-up of bags, which are slimmer and less rigid than 240L bins. Bags that were transferred to the top of the vehicle were picked up with the front of the grab in a 'tweezer-like' fashion.
  3. When a bag was picked up and lifted to the hopper, the bag wasn't released and dropped into the vehicle since the grab was designed to hold on to bins while emptied.

According to the manufacturer of the employed lifting arms, it would not be very difficult to rectify problems two and three (Iliff, 2002). It was assumed that lifting arms capable of picking up erect bags as well as bins could be built for approx. $2,000 more than a standard lifter. Picking up bags lying flat was seen as more difficult due to the problem of clearing the kerb with the grab, particularly where the kerb slopes uphill. However, it was thought that overcoming this problem could be done at additional costs of approximately $5,000. Conversion of an existing truck would cost approximately $4,000 and $7,000 respectively. These additional costs seem negligible if compared to the price for new waste collection vehicles, which range between $210,000 and $250,000.

The supply of compostable bags was quoted at $0.45 per bag (purchase of 10,000 bags). This price however does not include distribution to householders, which usually is a major cost component in bag collection schemes, regardless whether council, contractors or shops distribute the bags. The provision of compostable bags for fortnightly kerbside collection of organic materials incurs annual costs of $11.70 (plus distribution costs) per household. At costs of $46.80 per wheelie bin (quote by SULO for 1000 bins) and a depreciation period of 7 years, the use of bins seems more economical. However, costs and other aspects (depreciation, maintenance, finance, distribution, flexibility) have to be compared for both collection systems before a final decision can be made.

Impressions from the collection trial with biodegradable bags Impressions from the collection trial with biodegradable bags Impressions from the collection trial with biodegradable bags Impressions from the collection trial with biodegradable bags

Figure 50 Impressions from the collection trial with biodegradable bags