Anaerobic Digestion Makes Renewable Energy From Rubbish
A Waste Management system which is suitable for processing mixed (black bag) waste has been developed from technology first developed in Israel. It recovers resources from waste while producing renewable energy and helping to reduce carbon emissions. In other words it releases energy from our rubbish, and reduces the quantity of rubbish which might otherwise be sent to landfill, while at the same time reducing climate change. This is truly a win-win situation! The ArrowBio process has been developed through a series of pilot and demonstration plants to a level ready to be used commercially in many countries, and is best described as a water-based mechanical biological treatment (MBT) facility with energy recovery. ArrowBio’s process has been developed in such a way that it can either be used as a stand-alone solution or in conjunction with other technologies. For example it can be sited within sustainable energy parks to provide a source of energy as well as recycled materials for further processing.
The recycled materials are re-used as feedstock by the other businesses based within the park to create a variety of products. Two Stage Anaerobic Digestor ArrowBio sets out to fully recover and wash the recyclable elements of the waste, so it should be favoured by environmental groups which tend to object to alternative processes which handle mixed waste, like incineration, on the basis that the ability of incineration to handle mixed wastes reduces the necessity to separate and recycle. The argument is that incineration makes it too easy to neglect recycling, so it should not be used. The process has at its core a two stage anaerobic digestor which has been optimized for better energy yield than competing systems, from every unit mass of organic matter processed. Extracting the maximum available gas yield, is in fact a stated primary aim of the ArrowBio processs.
This is recognised as good policy environmentally, and of course the gas and, or electricity generates revenue, which helps to pay for the upkeep of the plant. The process consists of two distinct yet integrated components: a “front-end” wet Materials Recovery Facility (MRF) and a “back-end” advanced anaerobic digestion system. The wet MRF combines standard solid waste handling technology in combination with liquid and slurry pumping, water based processing facilitates, passive separation, and cleaning of recyclables and their automatic conveyance around the facility, while also suppressing odours and dust. In the wet MRF, the action of the water cleans, and recovers, ferrous metals, non-ferrous metals and plastics separated by type. These are then sorted into recycled materials of various grades that can be sold directly into the recycling market. A “hydrocrusher” has also been successfully developed by ArrowBio which forms part of the wet (anaerobic) process. In effect the biodegradable waste is jetted with high pressure jets of water through a series of pipes. Food and paper is torn apart, greatly increasing the surface area available to biological action, while simultaneously suspending the organic chemicals in a watery solution. Any waste that is not recoverable or that is not sent through the anaerobic digesters exits from the ArrowBio facility as a residue, and is normally present in only in minor quantities. The first part of ArrowBio’s anaerobic digestion process is known as the acidogenic stage, and the second is a methanogenic stage.
The biomass achieves optimum efficiency compared with single tank AD, and optimisation of pH levels, temperature and residence times is achieved automatically. The plant has low emissions. The ArrowBio design needs no costly gas scrubbing stage, and the largely water borne technique does not produce the troublesome (dust, odour, etc) emissions experienced from some other processes. Recognition of the sustainability benefits of Anaerobic Digestion in releasing energy from our trash is rising fast. Find out more about this technology for the future, at the Anaerobic Digestion Community web site, and more about the ArrowBio AD Process as well.
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