Process can be divided into two distinct phases:
1. Water based separation and organic
2. Anaerobic digestion, water cleaning and energy
In the first
section (a water-based MRF) the unsorted waste is processed directly
as tipped from the collection truck. Organic and inorganic materials are
separated through a unique, liquid-based technology, involving settling,
washing and hydro-mechanical shredding of organic solids.
In other waste treatment technologies such as incineration and
composting, energy is required to remove water from the waste stream.
However ArrowBio utilises liquids to their full potential.
The first stage end products are clean recyclable elements such as
metals and plastic (separated into PET, HDPE &
film plastic). These resources can be sent for recycling without need for
Items such as batteries are carefully
removed, without breakage, thereby voiding leakage of potentially toxic
materials. The other intermediary product is a dilute organic stream now
ready for the next, biological stage. The first stage thus performs two
functions; separation and preparation of the waste, without additional
machinery or effort.
In addition to removing inorganic and other
non-biodegradable materials, the liquid-based separation simultaneously
conditions the organic material for rapid biological action. This is
accomplished by bringing the organic matter into solution or fine
suspension. This slurry is very rich with a chemical oxygen demand.
In the second
stage the liquid is then sent to a series of tanks which support the
high-rate transformation of the organic wastes to biogas (on average 75%
CH4). This process is facilitated by naturally occurring microbial
communities, in two highly controlled sequential bioreactors. ArrowBio
utilises an advanced variant anaerobic digestion technique called up-flow
anaerobic sludge blanket (UASB) digestion. Biogas production by this
method far exceeds in-house energy needs.
The solid organic matter is thoroughly stabilised and usable
directly as an organic fertiliser. Excess water is either cleaned and
removed from the system or recycled and sent as liquid to the upfront
separation stage, and so the system is autonomous with respect to energy
The biogas is consumed by electricity generators,
producing five times the electricity the plant requires to operate.