Watership Down International Ltd is a UK company that designs, builds, installs and maintains a range of quality machines that incorporate the latest bio-technology techniques to recycle solid organic materials. We are also committed to continual improvement of our products through investment in research and development; and we have a dedicated team to support our machines throughout their life cycle which is measured in decades. We aim to create products that, as well as benefiting end users, local communities and the environment, also return cash value from waste.
The team at Watership Down International delivers:
- Organic waste processing products that convert food and other organic waste into fuel or energy:
- Creating heat for restaurants, factories, and housing from the food waste,
- Creating bio mass from agricultural and horticultural waste that can be used as:
- fuel for biomass furnaces and boilers
- soil improver component in compost
Advanced Organic Waste Digesters (AOWD)
Our AOWD’s are machines designed for combined efficiency in materials handling and biological activity. The machine core is a highly controlled environment to optimise aerobic and thermophilic bacteria action at temperatures in excess of 60°C. This produces clean, safe biomass in less than 36 hours
- Our machines are designed to be located on site to minimise waste transportation.
- Each unit is designed to have a small footprint and is delivered ready to connect up and use.
- Our machines are designed to digest the waste in 4 days or less to its maximum degradable amount, while, at the same time taking in the same quantity of organic waste on a daily basis.
- The unit has built in systems to eliminate any foul odours from within the machine so it can be placed near to buildings and in public areas
- Additional machinery required to complete the installation such as auger feed units, liquid waste treatment equipment, shredders, and hopper units can be provided and installed as required. All additional units provided are designed to be controlled by the same systems as the AOWD machine.
- Operating equipment and water reclamation systems can be provided in separate modules for positioning and attachment once on site.
- A suitable control room is provided to house all machinery control systems.
- Digestate, the product exuded at the end of the process, contains all inorganics based on the waste loaded into the machine. The only reduction is from organic material digested and water removed.
- The heat required by the process is normally maintained without the use of a heating system. Heaters are fitted for the start-up phases of the AOWD. The maintenance of the temperature required for the process is by the active use of thermophiles with nutrient augmentation to minimise operating costs.
- Heat pads can sometimes be used to increase machine temperature when necessary. Normally this is caused by variances in organic composition, ambient temperatures and water content
- The end product is pathogen free and ready to be used as Refuse Derived Fuel, Soil Enhancer, Biomass fuel or sent to landfill depending upon its contents.
- The output can be optimised for biomass fuel production. Alternatively, it can be set up to eliminate as much digestate as possible. Feeding digestate back into the machine can reduce output to almost zero.
- Each machine is able to recover as a minimum 65% of all water entering with the waste and provide this as a reusable water source. (Further treatment may be required depending on application or disposal route).
- The loading of the fresh waste each day is documented and controlled within an integrated computer monitoring system
- The collection of the water and the process to recover it, is also monitored and recorded
- The bacteria survive the process and just require topping up periodically. They are safe to handle at ambient temperatures, and they have a storage life of a minimum of 1 year.
- Bacteriological cultures come from sustainable sources. The Bio-Stimulants used within the machine are approved by Organic Farm Growers or Soil Association in the UK as safe for organic farms in respect to use of Digestate as Fertilizer.
- We usually provide a minimum two years’ worth of consumable products for each machine and we continue to supply these products for the term of the maintenance contract.
- The digestate (waste) that leaves the machine at the end of the process has been found to have significant calorific value at 75% the calorific value of coal. It can be used to fuel a bio-mass boiler to produce hot water, chilled water or electrical energy.
What is the problem with waste?
There is a strong correlation between the volumes of solid organic waste and GreenHouse Gas (GHG) emissions. Globally waste volumes are increasing quickly and established methods of dealing with the waste such as landfill contribute to GHG -related climate change.
Therefore there is an imperative to reduce waste and to process whatever waste cannot be eliminated using methods that do not involve GHG emissions.
The World Bank has a rough estimate of approximately 1.3 billion tonnes of waste being produced now and that will rise to 2.2 billion tonnes by 2025. Generally between 21% and 40% (by weight) of municipal solid waste is organic, increasing to up to 45% if paper and cardboard are included in the calculation. Considering the investment that went into creating the organic waste (and the nutrients and energy contained in it) this is too valuable a resource to simply throw away.
Organic waste sent to a landfill rots under anaerobic (without oxygen) conditions, venting methane gas into the atmosphere. Methane is one of the ‘greenhouse gases’ that trap heat in the atmosphere, contributing to climate change. Methane is particularly bad in that weight for weight it traps 21 times more heat than carbon dioxide. Most organic waste in piles becomes putrid and smelly. It attracts pests like rats and flies if it is left to rot. Another World Bank estimate is that between 30 and 70 million tonnes of methane escapes to the atmosphere annually from landfill.
The waste hierarchy indicates an order of preference for action to reduce and manage waste, and is usually presented diagrammatically in the form of a pyramid. The hierarchy captures the progression of a material or product through successive stages of waste management, and represents the latter part of the life-cycle for each product.
The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste. The proper application of the waste hierarchy has benefits. It can help prevent emissions of greenhouse gases, reduces pollutants, save energy, conserves resources, create jobs and stimulate the development of green technologies.
In 2008, the European Union parliament included the five-step waste hierarchy to its waste legislation, Directive 2008/98/EC, which member states must introduce into national waste management laws. Article 4 of the directive lays down this five-step hierarchy of waste management options which must be applied by Member States in this priority order.
At the top of the hierarchy is waste prevention methods. For the shops, this means monitoring the food ordering process carefully and moving out stock on the edge of suitability, at reduced price. For food processing companies it means analysing work practices to eliminate waste.
Next comes re-use. An example would be distillery mash being sold as animal feed.
The waste hierarchy covers all materials so the next level of recycling includes sending glass and plastics back for reprocessing and inclusion in new products. Importantly, it also includes composting where waste is transferred into soil improver and heat which can also be used.
Fourth of the five levels is energy recovery. Anaerobic digestion and incinerators are in this category.
Finally, landfill which is the least favourable of all the options. Governments are persistently increasing the levels of disincentives for landfill use.
There are only five levels in the hierarchy which means the steps between them are massive. Our AOWD’s used to produce soil improver are one level higher in the hierarchy than anaerobic digestion and incineration. This means that current EU Government guidelines and regulations stipulate that every organisation should only send to anaerobic digesters, incinerators, or landfill, organic materials that are impractical to recycle, which includes biomass production in aerobic digesters, or be reused
Note that if a customer uses our AOWD to produce biomass for fuel then we are in the same category as an anaerobic digester.
Where is our waste going?
Landfill Organic waste in landfill decomposes without the presence of oxygen producing methane that escapes directly to the atmosphere. It is estimated that global methane emissions from landfill are between 30 and 70 million tonnes per year. As shown in the later table, methane has a huge global warming potential. Some landfill owners are attempting to capture this methane, but the proportion is small.
Landfill is the worst method of organic waste disposal with practically no recycling capability. Governments around the world are acting to eliminate, or at least minimise, its use
Incineration Friends of the Earth consider that incineration of municipal waste to produce electricity causes more carbon dioxide to enter the atmosphere than an equivalent gas fired electricity generation station, and consequently they assert that incineration cannot be classified as recycling. “Scrubbing” of exhaust gases remove many toxins, but still one ton of municipal waste can produce between 0.7 and 1.2 tonnes of carbon dioxide, and incinerators can also emit nitrogen oxides which have a global warming potential 298 times worse than carbon dioxide.
Incineration emits so much carbon dioxide that it is difficult to consider it a recycling method even though some energy is captured.
Anaerobic digestion Fermenting organic waste in an anaerobic digester produces a mixture of methane and carbon dioxide. The methane is generally oxidised in a furnace and vented to the atmosphere as carbon dioxide and water. What comes out of an A.D. unit depends on the input. One ton of pig slurry produces around 33 m³ of greenhouse gases (approx. 75% methane and 25% carbon dioxide) while one ton of barley can produce up to 875 m³ of gas. The economics surrounding A.D. units encourage operators to maximise methane production and this reduces the amount of biomass that exits the digester. The biomass is sour, its leachate must be prevented from contaminating the water table, and it can only be used for agricultural purposes after a fairly long maturation process that also vents GHG to the atmosphere.
Anaerobic digester operators optimise the process to produce as much greenhouse gas (methane and carbon dioxide) as possible. Solid waste is converted to GHG, which, directly or indirectly, are emitted to the atmosphere.