by Eize de Vries
Domestic and additional waste disposal problems are not just exclusive to rich industrialized countries. Many people are familiar with the depressing scenes of open waste dumping grounds near big cities in developing countries, where the poor search smelly rubbish mounds for valuable fractions like paper, plastics and metals. The salvaging at these places (often under horrific living and working conditions) can in fact be regarded as a type of partial waste recycling in its most primitive form. What the rich throw away under these circumstances becomes a source of income for the poor.
Whereas in rich industrialized countries, domestic, agricultural and industrial waste volumes are typically much larger, with a huge variety of thrown away products, materials and different fractions. A typical developed country’s waste ranges from biodegradable organic fractions (wood, fruit, vegetables etc.) to clothing and building materials (concrete, bricks, glass, metals and plastics). Old computers, televisions and other electronic devices are typically collected and processed separately, which is also the case for small chemical waste like batteries. During the past decades (toxic) chemical waste products and residues have been disposed of mixed in with domestic and other waste, or at specified dumping grounds, both legally and illegally.
What the two example situations have in common is the huge potential to reduce environmental and public health hazards while simultaneously optimizing total financial gain for individuals and society, believes Ton Koens of Multi Purpose Industries.
Land-use pressure
In countries without land-use pressure constraints, all types of waste are disposed of in landfill sites outside the populated areas. But sometimes open waste sites are in environmentally sensitive locations, which (under certain circumstances) can easily develop into environmental hazards and public health risks. Once a ‘disposed’ waste disposal site has been filled-up to a permitted maximum size, the site is often simply closed and the same practice continues at a new location.
Public opposition to waste disposal sites in or near inhabited areas is common. When an active or inactive landfill site is not sealed-off completely by soil or another protective layer, continuous exposure to weathering influences can introduce a number of serious negative side effects. Firstly, decomposing biological fractions produce nasty smells so the area attracts vermin and has an increased risk of disease. Secondly, the rotting process is part of natural attenuation inside the waste and it produces methane gas as well as N2O (nitrous oxide – laughing gas). Without counter measures these gases are released into the atmosphere. Methane gas as a side effect is known to contribute 24 times more to global warming compared to carbon dioxide, and nitrous oxide contributes by a huge 128 times more than carbon dioxide.
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Domestic and other waste recycling rates differ between countries. For example, the Netherlands is one of the world’s most densely populated countries and it is known for its relatively large agricultural and chemical industry sectors. The combination of large energy use in industries and agriculture, and high land-use pressure, are considered the main reasons why Dutch people need to recycle about 90% of their waste. By contrast there are developed countries where waste recycling percentages do not exceed 20%–30%. However, despite a history of successful waste recycling, the Netherlands still accommodates about 4000 closed landfills, which together occupy roughly 8000 hectares (19,800 acres) of valuable land. In addition, roughly 10% of these Dutch landfills are located in areas destined for urban development and/or industrial applications.
Sometimes these polluted areas represent a grossly underestimated long-term public health and environmental hazard – for instance when harmful chemicals and/or toxic substances infiltrate surrounding soil, ground water and/or surface waters.
Waste containment
Landfill containment has become a common and established policy strategy that has broad political support in the Netherlands. A common strategy is to ram in a steel wall a few metres deep around a contaminated location. This sealing-off measure is typically carried out in combination with a protective topsoil layer and with or without an additional sealing-off plastic fabricing.
The Netherlands already has many waste sites containing toxic chemicals that have been treated in this manner. Political preferences favouring long-time containment, in combination with monitoring for at least a 50-year period, is largely based on rather optimistic investment cost limitation considerations, argues Ton Koens. An alternative ‘radical’ strategy whereby the contents of a contaminated waste pit (and if necessary also the immediate surroundings) is completely removed and replaced by ‘clean’ soil, is not popular for similar cost reasons, he adds. An intermediate alternative whereby contaminated soil is removed to a depth of a few metres and replenished by new ‘clean’ soil is a third option. In all cases the contaminated soil that has been removed has to be cleaned by either thermal processes or otherwise.
Ton Koens condemns the Dutch landfill containment policy preferences on several grounds: ‘Containment plus monitoring for a 50-year period may sound attractive to politicians and other decision-makers from an investment/cost perspective. But the picture they present is incomplete and figures change dramatically when all cumulative public health, and other risks that can cause serious harm, are also taken into account,’ he says.
‘Take for example a 25-year-old waste site situated in the middle of a town and close to housing, say the site is known to contain oil-based products and toxic chemical fractions like printed circuit boards. As these fractions are by definition all non-organic, their toxic content remains largely intact for a period that by far exceeds the 50-year containment period that is commonly included in these comparative cost models. It is publicly known that responsible authorities will, in this specific case, continue to bear all annual monitoring and containment costs for an unknown, but very long period. However these costs remain hidden in the original cost comparison that in this case spoke in favour of the containment plus monitoring option.’
Waste mining
Waste ‘mining’ as a concept aims at benefiting from modern household waste containing a number of valuable fractions, each with different characteristics and all with potentially added value. With the aid of MPI’s innovative waste processing technology, individual fractions can all positively contribute to an economically viable business model, explains Koens. ‘A typical Dutch landfill contains biodegradable fractions as well as metals, plastics, glass, and other less valuable residues like rocks, bricks and cement.
‘As part of MPI’s business model we are prepared to buy existing waste sites for €1, provided the internal composition contains a proven ‘healthy economic mix’ of biodegradable fractions, metals and other valuable materials. In return, MPI carries out a landfill processing/total removal process at its own expense. A second condition is that the total added value, in terms of valuable end products and energy that can be sold on, solely benefit and belong to MPI. In return we totally eliminate a given landfill in terms of 100% volume reduction, and we deliver a guaranteed chemically clean site to the land owner.’
Other combination deals are also possible. In the past MPI unsuccessfully attempted to negotiate a deal with several municipalities in the northern part of the country – as governments normally prefer to deal with reputed players using proven technologies. After a study MPI declared the total clean-up of five chemically contaminated waste pits (four small ones with no added value content) for free, to be economically possible. The only condition was that MPI as a package deal could be allowed to buy the fifth waste pit with substantial added value content, in order to make the combination of projects feasible.
Modular system
For its waste site processing the company applies an in-house developed modular building block system called Multi Purpose Unit (MPU) – which is comprised of a series of different modules integrated into a single ‘closed-loop’ process chain. In order to achieve maximum flexibility and optimal process control, together with optimized installation size, each MPU is designed in the smallest industrial size possible.
Closed-loop process control means that the output (including heat and/or electricity) of one process module is reused as an input for the next module in the integrated process chain. This design set-up ensures optimized process efficiency as well as minimized process emissions. Each individual module is based on proven technology and has been developed by or in close co-operation with a dedicated MPI partner. The complete line can be controlled technically. The result is a flexible and efficient improvement against low investment costs, compared to what is considered routine today.
In a further explanation of MPI’s waste mining business model, Koens says the metal fractions contained in an average waste site cannot be compared with the raw materials they were originally made from: ‘Assume, for instance, a person by accident throws a knife away together with vegetable cuttings. This steel of the knife has a high grade purity – in the range of 95% ore, as compared to about 11% for iron ore mined in Namibia. Similar observations can be made for other material fractions found in a waste site like pieces of copper and steel piping, steel nails, electric copper wire, aluminium brackets etc.’
As a result, the metals recycled from such a place, by definition, possess high purity, which is reflected in the price made for them as high-grade end products on the world market. Besides high-grade metals, other landfill fractions can be turned into fuels – like synthetic diesel from hydrogen. A third potential income is in the form of energy, heat and/or electricity and energy carriers, like synthetic fuel or hydrogen gas. By capturing the methane in biodegradable fractions a modified diesel generator can produce electricity and heat. The electricity and heat can be partly used in the internal process, while the surplus is available for sale.
From building waste to synthetic diesel fuel
MPI’s field of business is rather broad and already expands beyond the clean-up of waste sites. In mid 2008 the market entrant launched a customer contract with a major building waste processing and recycling client based in the Dutch Utrecht province. Says a happy Ton Koens: ‘This contractor distributes containers to building sites where local building contractors and other people involved in building renovation/new building activities fill them up with residues and scrap material. A typical container contains multiple material fractions, ranging from pieces of concrete, cement, bricks, wood, copper cable pieces, copper and steel pipe, polystyrene foam, roofing material, carton, paper etc. After the containers are brought into the 3000m2 sorting hall, the contents are dumped on a large heap on the floor.’
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As a first sorting step the big fractions are taken out, and as a second sorting step, workers hand-pick certain fractions from a moving belt system. Underneath the belt smaller fractions settle down. These deposits are named screen fractions and include many high-caloric, often oil-based materials, like cable linings, polystyrene foam and roofing material, in addition wood, paper and cartons. Ton Koens says: ‘In the case of this specific contract, the estimated screen fractions add up to around 10,000 tonnes a year. When the material is disposed of at a refuse site, the costs involved amount to around €75 per tonne. As a genuine waste and process industry innovation, MPI will convert these screen fractions into synthetic diesel fuel, which in turn will be used to power the company’s trucks. The 10,000 tonnes of screen fractions equates to about 5500 tonnes of diesel fuel.’
Internal benefits for MPI’s client are two-fold. First, they save each year +/-€750,000 on screen fractions they do not have to dispose of anymore, and a litre diesel fuel cost at the moment is in the region of €1 per litre. The latter adds up to an additional saving in the range of +/-€550,000 based on today’s diesel fuel price level.
Working partners
Finally, for the so-called Syngas process technology, MPI closely co-operates with the University of Twente and the Dutch engineering consultancy Clean Fuels BV. The latter pioneered the technology and tested and optimized it to the current commercial stage.
Ton Koens says: ‘This contract marks MPI’s move into the huge waste processing market. In the coming months we expect to sign several more contracts with parties that are also active in the same market segment – of which there are already fifty in the Netherlands alone, and many more internationally. The nice thing for MPI and its partners is that each of these contractors has a comparable building waste sorting method. And as all of them face similar cost challenges, they can no doubt all benefit from technologies MPI can offer, now and in the future.’
After excavating the waste site in trenches the material flow is sorted out into the many different fractions. These fractions represent the bulk of the pit content which, after intensive cleaning and treatments, are converted into the correct purity and dimensions for industrial reuse. Thus exploitable materials, like minerals, metals, glass and certain plastics, find their way back to the market as a valuable raw material.
The non-exploitable content, mainly organic fractions – a kind of third generation biomass source – is further processed. After the required treatments, including mixing and buffering, it enters, as controlled input, the energy transition part of the process line. Here it is transferred into energy and/or energy carriers.
Eize de Vries is a journalist specialising in renewable energy and environmental issues. He is Wind Technology Correspondent for Renewable Energy World e-mail wmw@pennwell.com
