Staff Writer

Sustainable Insights: Growing Australia's waste and resource recovery industry…it's happening

Sustainable Insights: Growing Australia’s waste and resource recovery industry…it’s happening

Commercially it makes sense and as the sector grows nationally it will drive changes in community behaviour and understanding, boost economic development and jobs growth.

Unless we tackle waste reduction from every angle we won’t make the most of our potential.

The industry’s spreading its wings

A 2012 Australian Bureau of Statistics study found 98 per cent of Australian households took part in some form of recycling or reuse of household items. Read more

WMAA landfill conference: exploring the use of trommel fines as landfill cover

WMAA landfill conference: exploring the use of trommel fines as landfill cover

Speaking at the Waste Management Association of Australia’s 2017 Australian Landfill and Transfer Station conference at the end of March, Mockinya Consulting director Paul Lightbody told delegates the project started as a means to find a use for trommel fines produced at a refuse-derived fuel facility in Adelaide.

The plant, which was established in 2006, processed some 150,000 tonnes of construction and demolition and commercial and industrial waste a year to produce an engineered fuel.

The feedstock it receives is screened, goes through a size reduction process, and is then separated to produce process engineered fuel, aggregates, fines, as well as a small amount of residual waste that is landfilled.

“Two streams come out of this process – one’s a coarser stream and the other’s a finer stream,” Lightbody said.

“Parts of the equation that framed this project was to look at what these materials were, how they could be used, which characteristics might be important, and whether these materials and residuals could become a resource.”

At the moment, there is simply no local market for the oversized fines (12-40mm) and heavy fines (12mm minus).

Typically, these fines, which Lightbody said are “studied extensively”, are composed of inert mineralogical materials including plaster/gyprock (85.6%), organic inclusions (12.13%), glass (1.54%), hard plastic (0.17%), light plastic (0.02%), other miscellaneous materials (0.42%) and an almost negligible percentage of metal and foam.

Key considerations

Because of the fines’ composition, there were characteristics that Lightbody needed to evaluate.

“The issues for the use of these materials on landfill as cover were potential flammability particularly because there were visible inclusions of plastics. There was also potential for it to generate odour and further contribute to methane emissions in the landfill because of the organic fraction. It also needed to be suitable from a chemical composition perspective and we already were pretty satisfied about that in the quality of the material,” Lightbody explained.

Additionally, under the SA EPA licence requirements, landfill cover must be a “soil” and not a waste material although in SA, there is an exception for waste fill. Or, Lightbody said, the fines could be approved as an alternative cover under approved specifications. Thus, discussions with the EPA began around the parameters required for the fines to be used as an alternative cover.

Testing the fines

Lightbody noted that in Australia, there were few common methods have been used to test the flammability, odour and methane emissions, and physical performance of trommel fines as an alternative landfill cover, though these tests certainly exist.

He turned to the ASTM D4982 “flammability potential screening – waste” to test the material’s flammability and a static method based on the ASTM D5975 to test respiration activity in order to determine the odour and methane emissions.

“For the physical performance of this material, there hadn’t been a lot of characterisation of particle size distribution (PSD) so we looked at that to see how closely the methods were replicated for the fuel,” Lightbody said.

Mockinya performed initial tests on a stockpile of material in 2013 over 10 consecutive days, followed by a five-day test in 2015.

The results

“The ASTM method for flammability tested whether the material would be ignited easily and sustain a flame. This testing was undertaken by an independent third party laboratory,” Lightbody said.

The result was that no, the material did not ignite easily nor did it sustain a flame. All samples were later classified as not potentially flammable.

However, there was a small amount of flammable material present in the fines, specifically:

  • plastic and paper, which would ignite and burn when contacted directly with the flame. It would then smoulder for up to 15 seconds; and
  • larger pieces of wood, paper and plastic that would ignite and burn when contacted directly with the flame and remain burning for up to 15 seconds.

Extinguishment followed after, Lightbody said.

Turning to the respiration activity, Lightbody relied on a modified version of the ASTM method developed by the laboratory that used proprietary and independent techniques around the containment of the gas within the chamber. Table 1 details the differences in the respiration activity tests; the middle column is the test that was undertaken.

WMAA landfill conference: exploring the use of trommel fines as landfill cover
Table 1: Testing respiration activity. (Source: Mockinya Consulting)

The test revealed that the rate of oxygen consumption had decreased over time with the highest four-day rate at less than 1mg of oxygen per gram.

“We were looking for variability in the factors that might affect the results but the results were consistent. We started to look at shorter timeframes because we were seeing a plateau in the respiration rates and we did, over time, develop confidence that we were seeing good and consistent data and we weren’t getting significant outliers in the data,” Lightbody said.

“One of the benchmarks we developed as we went through this program was based on Irish EPA guidance around the use of residual material for landfill cover application, which established the criteria of between four and 10mg O2/g and we were seeing results that were well inside what was thought to be a reasonable target. Thus, the conclusion was the organic matter was biologically stable.”

Finally, when it came to particle size distribution, Lightbody told delegates that this was “relatively consistent across the material” over the two testing periods. There was quite a good gradient of material and a reasonable amount of fines content – coarser content that provided the material some strength that would make it suitable to be used as a cover material.

“Other discussion points were the presence of glass and the perception that there is a fire risk due to the glass in the material,” Lightbody added.

“This is a myth in Australia that glass on the side of the road causes bush fires and our own fire authorities do teach their firefighters that it is a myth.

“The volatile solids are also within the range of carbonaceous soils, so that wasn’t a concern. We looked at all the impacts, even the stability of the material and it benchmarked reasonably well against the current soils that are used for cover.

“In summary, it forms a dense cover, it’s well graded, and it physically limits direct access for vermin – it’s not a food source for vermin. It is also not generating odour.”

The waste inclusions were also not significant to function as a cover though they are within approved specification limits.

In terms performance, Lightbody noted that the material has been used as an interim cover for three years now and in that time, it has remained stable despite some very heavy rainfalls.

“It has been accepted now by the EPA,” Lightbody said.

Redback Technologies supplying energy management services in the UAE

Redback Technologies supplying energy management services in the UAE

Duserve FM is a wholly owned subsidiary of Dubai South, an emerging city with an expected population of one million that will be home to what is planned to be the largest international airport in the world.

With a focus on setting a global example as a sustainable city, predominantly powered by renewable energy, the new partnership will see Redback install its robust, scalable hardware and software solutions in 20 commercial and 20 residential properties. Read more

WMAA landfill conference: dealing with a leachate breakout

WMAA landfill conference: dealing with a leachate breakout

Speaking at the Waste Management Association of Australia’s 2017 Landfill and Transfer Stations conference last week, City of Darwin manager technical services Nadine Nilon told delegates the events that unfolded on January 17, 2014 have been etched on her memory forever.

On that fateful day, the council’s Shoal Bay Waste Management Facility noticed that leachate was leaking out of landfill cell four, marking the start of a six to 12-month process to clean-up, fix and review the situation. Read more

What is a solar energy landfill cover system?

What is a solar energy landfill cover system?

HDR’s innovative approach uses a highly durable geosynthetic cover equipped with laminate solar panels reducing cap construction, maintenance costs and providing a renewable source of power for a beneficial reuse of a closed landfill site.

Solar energy covers versus traditional systems

Traditional landfill caps include a geomembrane layer placed over a compacted soil base, a drainage layer (geocomposite/freely-draining sand), a protective soil cover, topsoil then grass to resist erosion and promote evapotranspiration (Figure 1). Failures of traditional caps often occur on sideslopes and are a result of slippage of closure components along an interface of dissimilar material.

A solar energy cover consists of an exposed geomembrane cover (EGC) upon which laminated solar panels are directly adhered.

An EGC provides a clean, stable, and relatively inexpensive closure system that reduces infiltration of precipitation into the waste mass and requires less maintenance with the benefit of being easily inspected to confirm its integrity and impermeability.

The EGC is attached to the landfill surface using anchor trenches to resist wind uplift forces. After installation, the EGC can be easily removed to access the waste or subsurface piping and reinstalled without the effort and expense of removing the soil cover and established vegetation.

Installation of an EGC can reduce the cost of closure by negating the requirement for vegetative support soil and top soil layers (useful when soil would otherwise be imported).

The effects of long-term exposure to the elements are well understood for many geomembrane materials, and these products can be used with confidence and warrantied against failure for periods up to 30 years.

What is a solar energy landfill cover system?
Figure 1: Solar energy cover vs. traditional landfill cover.

Laminate solar panels

Laminate panels can be adhered directly to a geomembrane on any area of the landfill where storm water does not pool. Their inherent flexibility is also more forgiving for undulated surfaces caused from surface grading or differential settlement due to waste decay/consolidation.

The efficiency of laminate panels has recently improved, and they can be spaced with higher density utilising a greater area as they can be placed on the crown and the sideslopes of landfills.

Maintenance and useful life

Panels will require cleaning, especially in arid climates, where dust from landfill operations tends to accumulate on the panels. Design life for laminate panels is approximately 20 years.

One manufacturer, First Solar, guarantees that their panels will produce 90% of the nominal power for 10 years, and 80% for 20 years (First Solar. 2009b).

Power generation

One of the most attractive features of a solar EGC is that it can be a source of revenue beyond the active life of the landfill.

Potential on-site uses include reducing the parasitic load of pumps, compressors and other equipment at landfill gas to energy facilities. The energy can also be used to power remediation systems and site operations or returned to the grid.

Case studies

HDR provided design, permitting and construction support services for the Hickory Ridge Landfill solar EGC (Atlanta, Georgia, USA). This project utilised an EGC design over 19.4ha with 4ha used for solar energy generation consisting of 7000 laminate panels to generate 1MW of renewable electricity.

The project provided benefits that include generating renewable energy, creating a revenue stream and eliminating erosion and dust. The laminate panels proved ideal because they are flexible, lightweight, require no bracing and thereby don’t add point load to the surface of the settling waste mass.

The laminated photovoltaic panels are approximately 6mm thick and generate electricity year round under high and low light conditions and temperatures. The system is designed so the panels can be easily replaced at the end of their useable life (with 20-year standard product guarantee to meet 90% of their rated capacity).

HDR has also completed a detailed concept study for a solar EGC at a landfill in Brisbane, Queensland. The study looked at applying a 2MW system to an area of approximately 4.5ha and the study indicated upside benefits of clean stormwater runoff and the ability to offset site generation needs whilst also feeding back into the grid.

Solar EGCs are increasingly being considered and successfully implemented at landfills throughout the world due to their significant benefits over a traditional cover.

The benefits that these covers offer landfill owners/operators include a more cost effective cover, improved stormwater runoff, and a renewable source of energy.

Judy DeVita, HDR principal civil engineer, is based in Brisbane while Kanishka Perera, HDR environmental engineer and Mark Roberts, HDR principal waste engineer, are based in Jacksonville, Florida. More: www.hdrinc.com.

This article was originally published in the February issue of Inside Waste.

Progress to 100% renewable energy in Victoria

Progress to 100% renewable energy in Victoria

These are ambitious targets and the following questions need to be asked:

  1. Are these targets being aimed for elsewhere?
  2. If so, what progress are these other countries making toward achieving these targets?
  3. In those countries what are the distinctive developments that are allowing such progress to be made?
  4. Does Victoria have similar policies, programs and progress to allow these goals to be met?
  5. What real actions are needed in Victoria to improve the chances of meeting these targets and goals?

Read more

Future Focus: Getting from a linear to a circular economy

Future Focus: Getting from a linear to a circular economy

We need to make changes to both, particularly the recycling system, at both the macro and micro level, if we are to grow into a more resilient and sustainable circular economy.

In a circular economy, already used materials and products are renewed, reprocessed and integrated back into the economy for overall greater productivity.

According to the National Waste Report 2013, for the period between 2010-11, around 40% of what we produced and used in Australia went to landfill or incineration. Read more

The state of the waste data

The state of the waste data

The SOE concludes that: “Despite an overall increase in waste generation, Australia’s total disposal tonnage decreased from about 21.5 megatonnes to about 19.5 megatonnes (about 9.5%) between 2006-07 and 2010-11. During this period, the resource recovery rate in Australia increased from 51% to 60%. The quantity of material recycled increased significantly from 21.4 megatonnes to 27.3 megatonnes per year, or by about 27%.” (Australian State of the Environment 2016, p.90) Read more

Sydney Markets' environmental upgrade continues with new solar array

Sydney Markets’ environmental upgrade continues with new solar array

The 640kW structure will save 936 tonnes of carbon each year – the equivalent of taking 522 small cars off the road annually – and was built as part of Sydney Markets continued commitment to environmental sustainability.

The extension will provide an additional 350 parking spaces in the multi-level car park, as well as a new 4.5 tonne goods lift.  Read more

Building a clear vision for waste and resource recovery infrastructure

Building a clear vision for waste and resource recovery infrastructure

One issue that should be high on the public and government agenda, which requires further debate and discussion is who really is responsible for the provision and planning for waste and resource recovery infrastructure in Australia?

Increasingly, we hear “let’s leave it to the market”. Is this, however, really the right approach, given the importance of waste and resource recovery facilities for both public health and amenity, as well as the need for these facilities to support the urban growth predicted by governments in almost all Australian states? As we all know, if there is ever an industry that encounters NIMBYism, it is this industry. So, is it really appropriate for government to simply “leave it to the market”? Read more