BioCycle April 2008, Vol. 49, No. 4, p. 49
The five regional councils in the Perth metropolitan area are systematically rolling out a waste processing infrastructure, realizing the benefits of compost for soils and climate change.
LOCATED in the southwest corner of Australia, Perth is the capital city of Western Australia, the country’s largest state. Despite its population of some 1.5 million, Perth is one of the world’s most isolated cities.
That isolation, however, has not stopped Perth from moving to the forefront of waste processing and resource recovery through a systematic roll-out of waste processing infrastructure. At the current rate of facility construction, it has been estimated that 570,000 metric tons/year (mty) of the municipal solid waste (MSW) stream, representing 100 percent of the total, will be processed by 2012.
Every West Australian home generates approximately 1.3 mt of MSW per household per year; of this, 0.71 mt is organic material. With some 700,000 domestic residences in Western Australia, this equals 490,000 mty of organics, which traditionally has been disposed of in a landfill. In Western Australia, the average organic matter in the topsoil ranges from 0.5 percent to 1.5 percent. There is a clear need for organic material to be recovered and reused.
The Perth metropolitan area is divided into five Regional Councils, each constituted from a number of individual local Councils. The Regional Councils are tasked with certain functions, including waste management, the majority of which have excluded the use of thermal processes as an acceptable approach. The Regional Councils are responding in support of the State Government Waste 2020 vision of “Towards Zero Waste.”
Southern Metropolitan Regional Council (SMRC)
The SMRC established Perth’s first regional resource recovery facility with construction of an in-vessel (Bedminster process train) system that has been operational since 2005. A materials recovery facility and a green waste processing plant, sized as follows, support the MSW composting facility: MSW composting – 100,000 mty; Materials recycling – 100,000 mty; Greenwaste processing – 40,000 mty. The combined asset is currently valued at $110 million AUD.
The two stage aerobic composting system begins with biodegradable separation in the segmented in-vessel rotating drum over three days. After primary screening, the second stage (maturation) is achieved by controlled “open windrowing” within an enclosed structure. The combined system produces compost for commercial sale, metals for recycling and residuals for landfill. The SMRC is also managing a program to add 50,000 mty of processing capacity through the installation of a second facility by 2012.
Western, Southeastern And Eastern Metropolitan Councils
The Western Metropolitan Regional Council has an agreement for installation of a small-scale plant that once proven will be upsized to a 55,000 mty commercial scale plant. The locally developed DiCom technology is a three part process consisting of mechanical screening to separate organic/inorganic fractions, followed by combined (one vessel) aerobic/anaerobic digestion of the organic fraction, and finally screening and composting of organics. The small-scale plant is under construction.
The South Eastern Metropolitan Regional Council (SEMRC) has undertaken community consultation and site selection, and established technology selection principles. It has excluded thermal technologies and has sized a proposed facility at 100,000 mty. The SEMRC is expecting to commence the tender process in the fourth quarter of 2008.
The Eastern Metropolitan Regional Council (EMRC) has undertaken community consultation, site selection and established technology selection principles. It has included thermal technology options and has sized a proposed facility at 100,000 mty. The EMRC is expecting to commence the tender process in the fourth quarter of 2008.
Mindarie Regional Council (MRC)
The MRC, the State’s largest waste management authority, manages the disposal of waste generated each year by some 500,000 people. It has signed an agreement with BioVision 2020 for the establishment of a 100,000 mty Conporec technology MSW composting facility. The $80 million facility is due for completion in mid 2009.
Conporec’s two stage aerobic composting system begins in the continual flow in-vessel rotating drum over a three-day period. After primary screening, the second stage (maturation) is undertaken in an automated agitated channel system within an enclosed structure. The combined system will produce compost, reclaimed metals and residual for landfill. BioVision 2020 will finance, design, build and operate the facility for a 20-year term.
The City of Stirling (pop. 187,000), although part of the MRC, has had access to a waste processing facility since the late 1990s. The Atlas system, a local development, is a two-part process consisting of a nonbiological drum with screening attached to the discharge end. The process relies on the drum breaking open bags and separating organics; water is used in the drum to promote the breakdown process. This trommel process is undertaken twice.
The second stage consists of a fine trommel to further screen recovered organics. The organic material is transported off site to a farm for open windrow composting. The final compost product is screened to reduce plastic and glass before application on the farm. The facility processes approximately 65,000 mty of MSW.
The SMRC, as the first regional MSW composting facility in Perth, sought and gained an $800,000 AUD grant from the State government to develop markets for MSW based compost. The outcome was the largest farm compost demonstration so far in Australia.
Forty-six demonstration sites were chosen, most within a 150 km radius of the SMRC facility. A diverse range of farming types and crops were selected, including wheat, canola, barley, wine grapes, turf, olives, stone-fruit, citrus and avocados. The project was undertaken over two growing seasons, with control (no compost) and compost treatments being set up on each property. Soil fertility (pH, moisture and nutrients) levels, plus indicators of plant growth and/or yield, were measured on all plots.
The project demonstrated outstanding improvements in soil fertility and crop yields using MSW compost. Soil fertility consistently improved in the area of soil moisture (up to 20 percent increase), organic carbon (up to 60 percent increase), pH (consistently reduced acidity) and soil bacterial ratios (aerobic to anaerobic).
Improved crop performance was highlighted consistently by extra plant growth (up to 33 percent), higher yields (up to 42 percent) and in many cases improved quality of produce. In broadacre crops, this was evident in many cases by improved plant dry weights and grain yield. In horticultural crops, improved performance was reflected in increased tree and vine growth rates, higher turf production, increased fruit yield and sugar content.
Cost benefit analysis of the use of the compost in horticulture showed a positive return in the application to viticulture, citrus and turf farming. However, transport costs were a significant barrier to broadacre cereal crop farming. Positive benefits were gained from compost in all three situations, indicating an obvious need to find cost-effective ways to use compost in broadacre application, such as pelletizing.
Surveys of farmers participating in the trial showed that 91 percent had a positive impression of the compost quality, 81 percent had no problem integrating the compost into their farm management schedule, 85 percent were prepared to pay freight costs, 86 percent were prepared to continue to use the compost and 82 percent would like to run trials with pelletized compost. Farmers also wanted to understand the impact of MSW compost on the soil heavy metal levels. After two years of compost application, there was no evidence that repeat applications of MSW compost increases the residual heavy metal levels in soil.
The investigation found that the market potential for the use of MSW compost within a 150 km radius of Perth was 2.5 million mty for broadacre farming and 630,000 mty for horticulture. Considering that the supply from proposed MSW facilities is 300,000 mty, there will be considerably more demand than supply in the future. The input cost of compost (with freight costs being a considerable component) will be the biggest hindrance to farmer use. Farmers will need specialized advice integrating compost into their farming practices by reducing other input costs.
The SMRC waste processing facility diverts the household garbage of more than 350,000 residents from the landfill. When disposal of organic matter to a landfill is avoided by composting, methane emissions are abated. It is the net difference in emissions between dumping in a landfill and composting that gives the SMRC its Verified Emission Reductions (VERs), which are also known as carbon credit offsets.
The process is independently audited under the stringent rules of the Australian Greenhouse Office (AGO)’s Greenhouse Friendly verification program. The AGO calculates a 900 kg of Carbon Dioxide equivalent (CO2e) for every mt landfilled, compared to 130 kg CO2e/mt produced at SMRC (mostly from power use). The net is 800 kg CO2e/mt, verified by AGO into VERs. The SMRC is currently receiving an annual income of approximately $1.0 million AUD for the sale of the carbon credits (about 90,000 CO2e mt sold at $11/mt).
Speaking in the State Parliament, April 2007, a member made the following observation: “The SMRC claims that the facility will prevent an average of 80,000 mt of greenhouse gases entering the atmosphere every year,” says Paul Llewellyn MP. “The facility is making a major contribution in its own way to reducing the otherwise problematic issue of greenhouse gases going into the atmosphere when waste is buried in the ground and creates methane and causes other problems. We can compare that 80,000 mt of greenhouse gases with a reduction of 90,000 mt of greenhouse gas emissions a year if the State Government, as it expects, purchases 20 percent of all of its power from the renewable energy by 2020. Right now, that facility is almost doing the same task that the State Government will be doing by purchasing 20 percent of its energy from renewable energy. It is a useful comparison.”
Paul Oakes is a principal of Quadro Australia, which works with both private and government clients in the field of waste. He has been involved in waste processing in Perth for a number of years, having acted as bid manager on both the SMRC and MRC tenders. He is currently advising the SEMRC on technical, tendering and commercial issues.
April 17, 2008 | General
Western Australia Reaches For Zero Waste
BioCycle April 2008, Vol. 49, No. 4, p. 49