From a sustainable development point of view, adopting advanced technologies is the way to go for promoting recycling and composting.
In 2018, despite municipalities’ efforts, for the most part, the life cycle of the products we consume still ends at the dump.
In order to reduce the environmental and economic impact of the landfill of waste, businesses like Anaergia propose technological solutions that help limit waste while producing quality recyclable materials and renewable energy in the form of biomethane.
To better understand the overall issues relating to the development and commissioning of this type of technology, read the following interview with Gabriel Laroche-Johnston, Director of Engineering at the Anaergia waste treatment facility in Limassol, Cyprus.
What are the main technologies that help identify and sort recyclable materials?
The main issue consists in sorting and separating the different components of waste to better identify what is recoverable. This is done manually on a sorting line, then mechanically by different types of rotating, vibratory screens that separate the materials according to density and size. However, in our Limassol facility, we use two key technologies to help recycle household waste at an unprecedented level.
First, the organic extruder press (OREX) exerts significant pressure on the waste to liquify any organic matter by forcing it to pass through a perforated matrix. This organic paste includes few contaminants and after being diluted and polished, it is sent to anaerobic digesters to produce biogas. The OREX enables our facility to extract 90% of the organic matter contained in the household waste.
Automated sorting through infrared detection is another essential technology used in the household waste recycling process. It helps detect recyclable materials such as plastic and paper by identifying their infrared signature and separating them with jets of compressed air. This technology also helps differentiate the types of plastic to separate:
- polyethylene terephthalate (PET), commonly used for water bottles;
- polyethylene (PE), used for shopping bags and milk containers;
- polypropylene (PP), often used for packaging.
These materials are extracted from the household waste, then cleaned and sold on the global plastic recycling market.
What is the recovery rate of the different waste components?
Every year we receive 140,000 tons of household waste at the Limassol facility, and 91% of the materials are recovered or recycled; 90% of organic materials present in household waste are recovered and 75% of any recyclable material. What’s left after the sorting process is dried and transformed into refuse-derived fuel (RDF). RDF is composed of all materials that cannot be directly recycled and is destined to be burned as fuel in cement plants.
Are there things that are not recoverable?
There are in fact few materials that cannot be recovered. It is inevitable however that the sorting and polishing process of recoverable inputs (such as organic and recyclable materials) produces inert waste that has no energetic or market value. For example, at the Limassol facility, the cleaning process for organic materials generates a clay composed of sand, rock and crushed glass. This inert residue is sent to the dump.
Aside from this type of waste that is created by the cleaning and polishing of the recoverable material, today’s technology leaves nothing that can’t be recycled, biomethanized or used as fuel.
How much energy can be generated from a typical facility? What happens to the residual materials after biomethanization?
The Limassol facility, which serves 250,000 residents, produces 2.4 MW of renewable electricity from the biogas produced by the organic matter extracted from household waste. The facility is therefore energy self-sufficient and even produces an electric surplus of 1 MW, which is sold to the national network.
Biomethanization is a biological process where organic matter is decomposed by microorganisms. This process transforms most organic matter into biogas. However, at the end, there is a small quantity of residual organic matter that cannot be processed in the same manner. This residual organic matter is dried and then used as fertilizer by local farmers. Through biomethanization, the Limassol facility manages to process 85% of the organic matter extracted from household waste, while about 15% is transformed into fertilizer.
What is the impact of commissioning such a waste facility?
Before the Limassol waste treatment facility was commissioned, all of the140,000 tons of waste produced annually by the region’s inhabitants were buried in an illegal dump that was not capturing any leachate. This practice led to the poisoning of the region’s groundwater, which is serious for an island like Cyprus where water is rare.
Since the facility was commissioned, all of the waste is gathered and treated, and only 9% of inputs end up at the dump. Solid waste is received, organic matter is treated using biomethanization, recyclable materials are recovered, and even the water that comes from the waste and dump is treated on site. Thanks to the advanced capture of recyclable materials, the topnotch level of the facility’s automation and the water and electricity self-sufficiency, the Limassol facility only charges municipalities €19 per ton of waste input. To compare, the average price for treating waste in Greece is €65 per ton and in Germany, it varies from €70 to €100 per ton.
In future years, which technologies could help improve this kind of facility?
As in several heavy industry sectors, integrating artificial intelligence into the control and automation systems would help make waste treatment facilities more efficient and competitive. Particular interest would be paid to the automated sorting of unacceptable or undesirable waste materials.
For example, combining wide-spectrum cameras and a shape recognition software that has access to a large database would make it possible to sort and automatically remove undesirable inputs such as fishing nets, batteries, electronic garbage, medical waste, etc. To date, it’s these undesirable inputs that are creating issues at waste treatment facilities because they cause production line stops or poison the anaerobic digesters’ organic matter.
Lastly, what does Quebec need to adopt this kind of technology to manage waste treatment?
For a company to adopt an advanced waste treatment method, the government must implement incentive measures to reduce the dumping of untreated waste. For example, if municipalities had to pay $150 per ton of waste sent to the dump, market laws would encourage the creation of facilities that could receive this same waste at a lower price since they would recover the materials and greatly reduce the volume sent to the dump.
10 Jul 2018 | Written by :