New Technologies
Over the next few years the waste management industry will undergo a fundamental change away from historic landfill disposal of non recyclable wastes to a resource recovery based disposal.
Whilst it is now universally accepted that the land filling of wastes will become more and more expensive due to the escalation of landfill taxes, there is also a movement towards looking at non-recyclable wastes as a potential source of green renewable energy.
At present the makeup of wastes disposed into landfill are both non-recyclable organic and non-organic. Whilst Organic and food wastes will decompose in a relatively short period of time, non-organic wastes simply remain in a suspended state. Within an existing landfill once the landfill cells are full, they are capped and sealed which then takes the decomposition of wastes from an aerobic to an anaerobic state.
After a period of a couple of years, the decomposition of wastes in an anaerobic state produces methane gas which is extracted from the sealed cells, this gas is then used to produce electricity. Is it not unusual for landfill gas to be extracted from a single landfill cell for up to 15 years after the landfill cell is capped.
As we move away from landfill as the primary method of waste disposal, we will start to see the splitting of organic from non-organic wastes. By presenting the wastes separate of each other the two wastes will presented to new treatments whereby their gas and or energy is released in a more scientifically controlled manner, to produce renewable energy.
Anaerobic Digestion
Anaerobic Digestion is a technology and has been used extensively in Agriculture some time.
In simple terms wet organic
and food wastes once separated from non organic wastes are shredded to a very small size (<10mm) and then turned into a slurry by adding water or other organic liquid wastes.
This slurry is then pumped into sealed tanks, monitored, stirred and the gas is extracted to be turned into renewable energy. During the digestion phase the slurry is closely
monitored and tested to ensure that a core temperature has been reached for a minimum duration.
After the digestion phase has been complete and the gas extracted from the process, the organic wastes are essentially stabilised. Once expelled from the tanks, this slurry has the potential to be land spread as an organic fertiliser, subject to analysis and agronomical matching.
Refuse Derived Fuel (RDF), Climafuel, SRF
Once the wet organic fraction has been removed from wastes, the non organic fraction and less volatile organics such as plastic, manmade textiles, wood, card remain. Whilst these have no potential for recycling due to contamination and lamination they will be put through a manufacturing process such that the end product will be used in power stations to produce electricity.
Again, in simple terms the non-organic wastes are put through a process or shredders, sorters and magnets to remove all ferrous, non-ferrous metals and certain plastics.
Once shredded and sorted, the floc product is stockpiled and thereafter either transported loose or in briquettes to power plant.
The end floc product is tested extensively and ongoing to ensure that moisture content, calorific value and heavy metals are maintained within the input specification of the power plant.
The RDF floc product typically has a calorific value higher than timber, though slightly less then coal.
The waste processing plant that we operate at our Thirsk site, already has the capacity to separate Organic wastes from non-organic wastes. As a waste management company we have always been at the forefront of innovative recycling. Whilst we continually push the boundaries of recycling, we also accept that energy recovery in a sustainable and renewable capacity has a great part to play in future waste treatment and disposal.
As we move forward with the development of our own AD and RDF production capacities, we will regularly post updates. Click the links below to follow our progress.
We have already made the pledge that Todd Waste Management will be landfill free by 2013.