SMRC aiming to exceed 90% resource recovery
The Southern Metropolitan Regional Council’s (SMRC) strategic plan for diversion of kerbside collected MSW, recyclables and green waste from landfill targets a 95% reduction. At a recent industry conference in WA the organisation’s manager of engineering services, Brendan Doherty, outlined the second wave of technologies and approaches being considered by SMRC to achieve the ultimate landfill diversion.
The first stage of the SMRC’s regional waste strategy which included the development of the Canning Vale Regional Resource Recovery Centre (RRRC) in 2001, is currently achieving 66% recovery of resources processed at the site.
“SMRC research and development projects have identified new technologies and operating approaches that may achieve target landfill diversion rates exceeding 90%,” said Doherty.
These include weekly collection of recyclables, pyrolysis of compost screening residuals and other waste to energy applications such as gasification and production of bio-diesel from depolymerisation of plastics residuals.
The Southern Metropolitan Regional Council (SMRC) is a Regional Local Government established under the Local Government Act 1995. Participants of the SMRC include the City of Fremantle, City of Melville, Town of Kwinana, Town of East Fremantle, City of Cockburn and City of Rockingham.
The RRRC operated by SMRC comprises a MRF for sorting co-mingled recyclables such as paper and cardboard and plastic, glass, steel and aluminium containers; a Green Waste Facility (GWF) for mulching clean green waste collected in bulk from verges and other sources; and a Waste Composting Facility (WCF) for the municipal solid waste (MSW) stream.
With all six member Councils delivering to the RRRC a total of 160,000 tonnes of recyclables, green waste and MSW would be received on an annual basis with 66% of the material diverted from landfill.
“At this intake rate a total of 54,000 tonnes per annum of residual waste would be generated requiring landfill disposal or some other form of further processing and recovery of energy and resources,” said Doherty.
A number of scenarios were modelled by spreadsheet analysis to assess the theoretical maximum landfill diversion rates achievable and the likely landfill diversion rates anticipated in practice.
The models included all kerbside collected waste produced in the SMRC region that would be processed at the RRRC including bulk green waste, recyclables and MSW.
The modelled scenarios were:
a) Current processing (Waste Composting + Recycling + Bulk Green Waste);
b) Current processing & Weekly recycling collections;
c) Current processing & Pyrolysis energy recovery from final compost screens residuals; and
d) Current processing & Weekly recycling collections & Energy recovery from all residuals.
“What the SMRC’s modelling found is that current processing resource recovery rate of 66% performed well against the maximum achievable recovery rate of 72%,” said Doherty.
“Recovery rates of 80% and above could only be achieved with a combination of weekly recycling collections and all residual wastes being processed by a waste to energy facility”.
The likely recovery rate of 69% for the weekly recycling scenario was based on the results of SMRC trials, predicting a 40% increase of recyclables in the recycling stream in practice.
The maximum recovery rate for weekly recycling required a 70% increase in recyclables in the recycling stream or an additional 28,000 tonnes of recyclables moving out of the MSW stream into the recycling stream.
“There is not enough capacity in the existing 240 litre fortnightly recycling collections to accommodate the yield of recyclables in the overall waste stream,” said Doherty.
The larger gap between the likely and maximum recovery rates for weekly recycling was due to paper and cardboard in the waste bin being recovered as compost in the current processing system.
“Although weekly recycling did not produce the highest recovery rates consideration also needs to be given to the income potential of the recovered recyclables,” said Doherty, “net cost per recovered tonne and the established nature of the technology and markets when comparing to the waste to energy scenarios”.
In conjunction with waste to energy facilities Maximum recovery rates exceeding the SMRC target of 95% could be achieved by broadening the markets and alternative disposal opportunities for residual wastes such as:
. textiles, clothing and household junk;
. general mixed and thin film plastics (other than containers);
. inert wastes such as concrete, masonry and sand etc; and
. char and bottom ash from waste to energy processes.
Glass represented 10% of the overall waste stream and the stated recovery rates are therefore highly dependent on markets being available for all mixed glass in Perth.
“The adoption of a strategy is recommended to establish small scale waste to energy facilities for specific residual waste streams to prove the technology locally and gain community understanding and confidence,” said Doherty.
He said further work is recommended to include assessment of carbon, community and cost aspects of the scenarios modelled.
Source: Inside Waste Weekly