Landfill Gas Extraction System
What does the landfill gas extraction system do?
SBI have installed a landfill gas extraction system and flare which is consistent with best practice landfill management and will address odour impacts from the landfill gas. The system is now operating and undergoing calibration to maximise performance over the coming weeks.
How does the flare operate?
The flare operates as part of the landfill gas extraction system. Extraction wells drilled vertically into the landfill extend to near the landfill’s base. These wells are made of slotted pipes that extract gas generated by the landfill, which is then drawn through the pipes to the surface and pumped into the flare. The flare then mixes the gas with oxygen so it can be combusted – methane in the landfill gas is converted to carbon dioxide and water; and hydrogen sulphide is converted to sulphur dioxide and water.
What gasses are created from the flare system? How do you know the gas entering the atmosphere is safe?
Combustion of the landfill gas using the flare destroys the odourous hydrogen sulphide and methane from the landfill gas. The combustion of hydrogen sulphide creates non-odorous sulphur dioxide as a by-product. The methane combustion converts methane to carbon dioxide and water.
This flaring process is a condition of operation of the landfill gas system and is used to assess the system’s performance including how efficiently it is operating and impacts on air quality.
How is ‘continuous flow’ achieved?
The landfill gas flare operates continuously 24 hours a day by pumping the landfill gas at a rate equivalent to the landfill gas generation rate.
What happens when it gets very windy?
The flare is fully enclosed so it is difficult to extinguish, however an ignition system is in place to reignite the flare in a similar fashion to an auto igniter on a gas hot water system.
Does the flare go out? If so, does this effect the gasses being released?
Once the system is fully calibrated and performing at optimal efficiency, if the flare were to go out due to some mechanical problem, the pump and valves will automatically shut down to prevent gas emissions from the pipe network. It would take a significant time period (approximately 24 hours or longer) before landfill gas pressures built up to the point where gas emissions from the landfill became a concern.
How do the flare’s emissions impact the environment?
Capture and flaring of landfill gas destroys the methane in the gas that is a potent greenhouse gas. The combustion of landfill gas also destroys hydrogen sulfide that can be odourous even at very low concentrations.
Does the flare create increased fire risk and how is this managed?
The flare is fully enclosed. The flare will be protected from the risk of wind-blown litter crossing over the top and igniting it through the installation of a cage preventing material coming in contact with the flame.
The gas flare will be incorporated into the site’s existing bushfire management plan and complies with requirements set out by Energy Safe Victoria as part of the system’s permit conditions.
How will the new system be more effective?
The new system is able to capture and actively remove landfill gas from the landfill cell, and then flare the odour-generating gases before they enter the atmosphere. This flaring process eliminates the odour.
Has this gas extraction system been approved by the EPA?
The system has been installed to meet the requirements of the Environment Protection Authority’s Improvement Notice required for completion in August 2022.
How deep do the wells for the gas extraction system go?
The wells are dug to within three metres of the bottom of the landfill cell.
Why did it continue to smell after you pumped the liquid away?
In recent months, SBI has been addressing two sources of odour being generated from the landfill in Cranbourne.
Odour generated in late June was related to stagnant water pooling onsite, which has since been removed.
We are now focused on addressing the underlying issue of odourous gas being generated from the landfill cell as the waste breaks down.
To address this issue, the onsite gas extraction system onsite has been upgraded. Additional wells have been drilled into the landfill cell to capture, extract, and treat odour generated onsite.
We have also deployed a range of other measures to mitigate odour being generated onsite including onsite odour suppressants, and application of additional clay and rock covering to the landfill cell.
Why did it take so long to resolve the odour issue?
The landfill gas extraction system was designed and purpose built, which required specialist input, design, installation and connection.
How will you prevent this from happening again in future?
The new landfill gas system extracts and eliminates odourous gas from the landfill. The system can be expanded as the landfill cell is added to.
What happens to these gases in the atmosphere after they are burned?
Flaring is a common practice to mitigate odour at landfills. A model will be completed to ensure compliance with Environment Reference Standards in Victoria.
What monitoring of gas emissions, the landfill gas extraction system and flaring system will you have in place?
The landfill gas extraction system is being monitored on an ongoing basis, with further periodic testing used to inform any adjustments required and a monitoring plan being determined guided by advice from landfill experts.
Why does it smell worse at some times than others?
Atmosphere and wind direction are key factors. During still and cool conditions the atmospheric boundary layer acts like a lid preventing the gas from dissipating.
What are the remedial notices EPA has issued?
For more information about the Improvement Notices issued to SBI you can visit the EPA website (https://www.epa.vic.gov.au/for-community/incidents/sbi-inert-landfill)
What else does SBI need to do in response to the notice?
A condition in EPAs notice was the appointment of an Environmental Manager at SBI. For the duration of the sites operation a full time subject matter expert is now located at the landfill.
What is the lining of the landfill cell/void made of?
The landfill cell and quarry void is lined with a two metre compacted clay liner (CCL), a High Density Polyethylene (HDPE) liner as well as a protection geotextile layer designed to suit the specific conditions of the site and to prevent any leakage of landfill material outside the cell.
How is leachate captured?
All leachate generated onsite is contained within the landfill cell. After it is collected and pumped it is stored onsite and then taken to a licenced facility in Dandenong for testing and treatment.
Where does leachate from SBI landfill go?
All leachate from site is currently sent to a licensed processing facility in Dandenong. This includes hundreds of thousands of litres of water leachate that was removed offsite in June and July 2022. No leachate is currently sent to the ponds on Stevensons Road.
The licence says waste water can’t be discharged from site, so why can suction trucks remove waste water?
Any water that comes into contact with waste in the landfill cell is contained by the cell’s lining and pumped into tanks on site (forming part of the leachate). Suction trucks remove this material from site and take it to a licenced facility where it is tested and treated accordingly.
The term discharge in this case refers to the waste water being released directly from site without these controls in place.
How is storm water being collected onsite? What steps are being taken to prevent pooling of water onsite?
Extra steps have been taken to capture any surface water in the void and direct it away from the landfill cell.
This water is captured and drained from site as per the site’s Surface Water Management Plan.
How is storm water managed?
Stormwater is managed onsite in line with our Stormwater Management Plan. Just like any infrastructure site, it is designed so that water captured onsite flows away and into the stormwater system.
The design of the system is separate to management of water that may enter the landfill cell. The lining of the cell prevents water leaving the landfill cell.
Landfill management and accepted materials
How is landfill contained in the landfill cell?
The landfill cell is lined on the bottom and sides to prevent leakage of leachate and gas outside the cell.
What is the process for accepting landfill?
As a part of the waste acceptance process, all trucks must go over the weigh bridge where licence plate data is collected, loads are weighed further identified using cameras.
From the weighbridge waste it is tipped, screened and separated for recycling materials in the screening area.
Once these steps are completed the remaining waste is then placed in the landfill cell where daily cover is applied.
Do you accept liquid waste at the landfill?
The landfill site accepts only solid inert waste, construction and demolition waste, and commercial and industrial waste.
As part of this, the site does accept some Non Destructive Drilling (NDD) mud, which is the drilling mud remaining from drilling operations, made of soil and potable water. This mud is collected and evaporated in a separate pond onsite.
Is storm water accepted at the site and why has the website changed?
This was an error. We have since corrected this section of the website to note the waste that is accepted.
Does the site accept asbestos?
SBI does not accept asbestos material.
The landfill site accepts only solid inert waste, construction and demolition waste, and commercial and industrial waste.
Some companies that take construction and demolition waste also specialise in asbestos removal and have trucks advertising both of these services.
Trucks that transport priority materials like asbestos must use the EPA’s Waste Tracker to notify where and how the material is being disposed of.
Where any asbestos is identified in a load, our Asbestos Management Plan is enacted. The area is cordoned off and a licensed service provider is contacted to remove and dispose of it at an appropriate licenced facility.
How long will it take for the landfill to be full? Is the landfill likely to be filled before the licence permits?
A timeline on how long it will take to fill the landfill is difficult to estimate as it depends heavily on the volume of material being deposited in it. As a relatively young landfill, the site is approximately 10-20% full.
What type of clay is used for cover and where is it sourced?
Clay used for capping is a low permeability, site derived silty clay which is in line with best practice.
What association does this site have with Stevensons Road landfill?
There is no association between SBI landfill on Ballarto Road and Stevensons Road landfill.
Stevensons Road itself was named after our grandfather, who built the road in the area after World War Two. The landfill on Stevensons Road was operated by the Shire of Cranbourne. Our family was not involved in the operation of this landfill.
We operate the landfill on Ballarto Road under the name Stevenson Brothers Industries, shortened to ‘SBI’.
I have seen trucks heading to or from your site disobeying road rules – what are you doing to improve driver behaviour?
We take all reports of negative driver behaviour seriously. We instruct drivers to drive obey traffic signs, and require them to use the onsite wheel wash as they exit the site to reduce soil leaving the site.
What measures will be put in place to improve the condition of Ballarto road?
All trucks exiting the site drive through a wheel wash to remove excess dirt from their tyres. In addition, a water cart and street sweeper operates full time to help suppress dust and maintain the condition of Ballarto Road.
Over many years SBI have contributed to road upgrades and maintenance of Ballarto Road and will continue to work with the City of Casey on future improvements.
What time do works start on site?
The site accepts trucks from 7am each morning. Staff are onsite from 6.30am to prepare to accept deliveries.
Except where emergency works may be required, no machinery operates prior to 6.30am.
Are any further earthworks planned in the quarry void?
Quarry works are now complete and the site is now a landfill operation.
Some earthworks are required to shape the sides of the void for the landfill liner system.
Does the fence go all the way around the site?
The SBI site is fenced around its perimeter, as well as native vegetation.
Did the landfill license get extended?
The license doesn’t have an end date, it expires when the landfill is full.