June 26, 2006 | General

Controlling Odors, Making Compost At North London Center

BioCycle June 2006, Vol. 47, No. 6, p. 59
Built in only five months, new facility with neighbors close by receives up to 140 metric tons/day of green waste and kitchen residuals.
Harry Waters

Officially opened in March 2006, the LondonWaste Composting Center is on target to divert some 30,000 metric tons/year of organic feedstocks from the landfill. The plant uses an in-vessel process pioneered in the United Kingdom (UK) by a company called Agrivert. Established in 1994 to manage organic residuals, it was one of the first companies to anticipate the potential of the UK composting market. Its annual sales now exceed £10 million.
Located in the Edmonton EcoPark, close to London’s North Circular Road, the site is ideal concerning accessibility to the boroughs it serves. However, with industrial neighbors only 50 meters away – and residential housing 350 meters away – odor management was a major consideration when selecting a composting system.
The Compost Center cost approximately £5 million to build and covers 2.5 acres. The cost of the new state-of-the art center was covered by £3.5 million provided by LondonWaste and £1.7 million of government funding. LondonWaste is a public private partnership. The company is half owned by the North London Waste Authority (NLWA), a consortium of seven North London boroughs. The other 50 percent shareholder is waste management company SITA UK. At present, the company provides waste disposal services for the NLWA.
The government support was provided by the Department for Environment, Food and Rural Affairs, (DEFRA) through the London Recycling Fund, a fund established to help encourage waste minimization and to improve recycling and composting services in London. In total, the London Recycling Fund has provided £4 million to expand composting services in North London. As well as part funding the Compost Center, the £4 million grant, the largest single grant awarded by the Fund, is being used to buy additional vehicles to collect the food and garden waste from peoples’ homes and for household compost collection “bins”. Some of the money is also being used for community composting projects and training.
The Composting Center is operated on behalf of LondonWaste by Agrivert, which receives an operating fee per ton of waste handled, with a minimum guaranteed tonnage. LondonWaste recoups its costs through gate fees. LondonWaste has taken great care to act as a “good neighbor,” building strong links with the surrounding community, including local government and residents. Since the facility opened, a number of events have been held at the plant, so local people can see first hand what happens to their waste and how the composting process works.
The primary feedstock for the plant is green waste and kitchen waste. While the ratio of green to kitchen waste is currently around 80:20, the percentage of kitchen waste is steadily rising, as the local population begins to appreciate the benefits of recycling waste from their kitchens. Each of the boroughs it serves running its own curbside collection system. Some collect single waste streams and some collect organic and dry recyclables simultaneously, in dual collection vehicles.
Up to 140 metric tons of kitchen and green waste are processed at Edmonton per day. The plant reached its operating capacity within two weeks of opening, and has been working at that level ever since.
The plant uses the German Biodegma IVC (in-vessel composting) design, selected for its ability to control odor. Research studies at the Obersontheim composting plant in Germany have confirmed the effectiveness of this IVC technology in minimizing odor emissions. This plant – in operation since June 1998 – treats about 25,000 metric tons/year of kitchen and green waste. To date, the Biodegma IVC technology has been employed in about 30 plants across Europe, processing over 700,000 metric tons/year of organic materials.
Though the Edmonton plant is highly engineered and computer controlled, it was built by Agrivert in just five months. Rapid construction was possible in part because of the technology’s modular design – which enabled most of the component parts to be assembled off site ready for erection in situ. The modular design also lends itself to easy expansion, though it is not anticipated that the North London plant will expand, due to its urban location and restricted footprint.
To counteract the harshness of the composting environment, the Agrivert IVC design makes widespread use of corrosion-free material such as stainless steel, coated aluminum, concrete and Gore-Tex© roofs and doors. The roofs and doors are designed to act as barriers against odor; the fabric is a semipermeable membrane designed to let moisture vent freely but contain odor and bioaerosols. Overall, operational costs are lower, since material handling costs are reduced. Significant savings in energy are possible, due to the low power consumption of the fan system needed.
The IVC process works as follows. On arrival at the reception building, waste material is shredded and blended, then transferred to Stage One tunnels by a loading shovel. In the tunnels, the compost quickly reaches temperatures of >60° C and stays at this temperature for the duration of its time in the composting tunnels.
The significant capacity of tunnel area available at Edmonton (6480m?) means the waste can be retained in the tunnels for long periods. The retention period is typically five weeks – two-and-half weeks in Stage One and roughly the same time in Stage Two tunnels – with the waste material being turned and mixed on transfer between the two tunnel stages.
Since the composting material remains in the tunnels during the whole of its active degradation period and is not placed on the maturation pad until it is less active, the risk of odor is greatly reduced. With the maturation pad having a small footprint (1,125 sq m), the site has to be worked hard, with regular turning. The maturation retention time at the center is eight weeks, bringing the total composting period to 13 weeks. Regular screening is required to ensure there is space to keep a smooth passage of compost through the plant.
By the end of the composting process a 50 to 60 percent loss in mass has occurred. Once screened, any oversize organic matter is recomposted. Any remaining contaminated material is removed. Contaminated material of this kind represents only about 1.5 percent of the total waste and is taken to LondonWaste’s Energy Waste facility.
The Edmonton composting facility serves seven North London Boroughs -Hackney, Camden, Islington, Waltham Forest, Enfield, Haringey and Barnet. Barnet currently recycles about 27 to 30 percent of its household waste, making it one of the highest performing London boroughs. The borough has been running a composting service for garden waste since September 2002.
Until the new Composting Center opened, the garden waste was taken to Edmonton to be composted in an open-air facility. “However, we wanted to expand the provision in order to provide a better service for our residents and bring us closer to reaching the 2005/06 recycling rate of 27% set for us by national government,” says Nicola Buck, Environmental Services Manager-Waste Strategy for the London Borough of Barnet. “For that we needed a more high-tech approach and funding to expand our collection service.”
Because the IVC facility was built with funding from the London Recycling Fund, that enabled the service to be extended borough-wide. In October 2005, the borough began accepting kitchen waste alongside green waste from its residents.
“As the collection authority, we are interested in collecting and composting as much waste and as many types of food waste as possible,” Buck adds. “We want to make it easy for residents, as the easier we can make it the more likely residents are to take part. We’re also raising awareness through an extensive publicity campaign.”
Barnet’s strategy seems to be paying off, with around 57 percent of the 90,000 households offered the scheme, currently participating. “For a London borough that’s pretty good. We’re very pleased with how it’s going,” notes Buck, “though there is always more to do.”
End products produced by the IVC system are high quality and comply with all relevant UK regulations. These include the British Standards Institution’s Publicly Available Specification for Composted Materials (PAS 100), which sets a minimum compost quality baseline (see article in this BioCycle International section on PAS-100), and the 2003 European Union (EU) Animal By-Products Regulations (ABPR). The EU regulations were introduced in the wake of the devastating foot-and-mouth disease outbreak in the UK in 2001 and greatly tightened the rules governing the processing, use, disposal, trade and import of animal by-products.
LondonWaste is responsible for compost marketing. So far, about 350 metric tons have been earmarked by each of the London boroughs taking part, to be used as a fertilizer and soil conditioner in their parks and gardens. In addition, more than 2,000 metric tons have been blended with soil and are being used in turf cultivation. The remainder is being marketed to local land restoration and agricultural industries.
Already the UK’s compost producers represent a significant movement in the waste management sector. Between them in 2005, the 60 UK producers who are members of The Composting Association, the industry’s certifying body, produced more than a million metric tons of high quality compost.
The UK’s arable market alone could absorb over 50 million metric tons of compost per year, it has been estimated. At current compost production levels, there is still plenty of scope in the UK for finding sustainable markets for compost.
Harry Waters is Marketing Director of Agrivert, one of the largest recyclers of organic feedstocks in the United Kingdom.
With a growing population and a critical need for recycling and waste treatment facilities within its boundaries, London has been seeking waste handling and processing services. One response to this need is the LondonWaste EcoPark, under development in North London by LondonWaste, a public-private solid waste management company in the United Kingdom. In addition to the new Composting Center described in the accompanying article, the EcoPark will house recycling facilities for metal, paper and wood, aluminum and refrigerators. The EcoPark will combine the recycling services currently available and will include a state of the art materials recycling facility as the next development, with construction scheduled to begin in the summer of 2006.
The Energy Center converts waste that has not been recycled by households into electricity. The plant uses the heat generated from controlled combustion of the refuse to produce steam. The steam is then taken off at high pressure to drive turbo alternators that generate electricity at a rate of 32 mega-watts per hour – sufficient to meet the electrical needs of 24,000 homes.

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