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Organic innovations
02-MAY-2005

With landfilling out of favour, the Netherlands
has generally opted for incineration for treating organic waste. Now, a recent
entrant to the Dutch biowaste market is using its own anaerobic fermentation,
bio-stabilization and tunnel composting processes to manage solid waste without
the need of pre-treatment.

Established in 2000, Orgaworld is an innovative, fast-growing Dutch biowaste
treatment company that currently owns and operates five waste processing plants
spread across the Netherlands. Orgaworld¿s sixth plant is under construction
and the building work on a seventh is envisaged to start in September this year.
These latest developments mark a change in company strategy, as the previous
five plants were acquired from third parties and modified to suit Orgaworld¿s
demands. A recent joint-venture deal with a Portuguese company marks the start
of an international expansion strategy.

I visited two of the company¿s existing plants, situated some eight or so kilometres
apart at Lelystad in the province of Flevoland. The first was Orgaworld¿s surprisingly
simple anaerobic BIOCEL^® fermentation plant and the second was a
dry composting plant that produces the compost sold under the Orgapower brand
name. Both are engineered around similar modular design principles. Managing
Director Henk Kaskens provided tours of the two facilities and showed me specific
product and process features. He also gave me his views on current and optimized
waste treatment strategies and how Orgaworld aims to turn its ambitions into
practice.

THE ORGAWORLD VISION

Henk Kaskens recalls that making an entrance as a newcomer in an established
Dutch waste processing market with a limited number of large players, often
state-controlled, did not prove easy. The Netherlands¿ largest waste contractor
is the huge energy and water utility, Essent (100% state-owned), which controls
60% of the national organic waste market.

Kaskens says: `It is our company vision to reuse waste materials in the most
efficient manner in order to maximize both environmental and economic advantage.
The common view in the Netherlands to regard waste as a source of ¿renewable¿
energy is, in our view, mistaken.¿ He believes that bioenergy will shortly
have an important role in total energy production and that waste-to-energy
will continue to have a far less important role. He stresses that waste combustion
has a low energy efficiency and that the focus on producing energy from waste
often means that the quality of the other products from the process is overlooked.
This can result in emissions, ash and other residues causing problems for
the installation¿s owners. `The BIOCEL process may not have the highest biogas
yield but its product is high-quality compost (black soil in the Netherlands).¿

`We therefore profile ourselves instead as an innovator and maker of high-quality
products, including biofuels, from waste. But possessing potentially winning
waste-processing technology as a newcomer in the industry is only one thing.
Buying market share, we found, is a completely different issue. However, lobbying
on the basis of our arguments has so far proved effective. Waste processing
is also capital-intensive, but five years ago we were lucky to find the right
shareholders with trust and confidence in our plans.¿

Waste processing companies generally prefer to extract waste fractions such
as metal (both ferrous and nonferrous), plastics and inert materials at an early
stage of the process in order to optimize the feedstock for incineration or
other purposes, and to obtain revenue (e.g. from the metal fraction). Their
key marketable product is energy ¿ mainly electricity and sometimes also heat.
By contrast, Orgaworld concentrates on creating added value by processing organic
waste into reusable products; the production of energy is regarded as a valuable
by-product. Among these marketable products are:

• compost for organic soil enrichment


• bio-stimulators aimed at promoting plant growth


• bio-fertilizers as an alternative to energy-intensive mineral fertilizers
  


• bioenergy (biogas and, in the future, also bio-ethanol).

Henk Kaskens believes that Orgaworld¿s business philosophy coincides well with
EU environmental policies and new European waste directives. These focus on
the diversion of organic material from landfills, on energy recovery, and on
a reduction in Europe¿s dependency on energy from the Middle East.

DUTCH LEGISLATION FORCES WASTE MANAGEMENT CHANGES

The Netherlands is a small, densely populated, industrialized country where
the negative effects of uncontrolled landfill activities were more quickly apparent
than in larger countries blessed with more abundant land space. The Government¿s
current waste policy is largely based on the principles laid down between 1988
and 1991 when the decoupling of gross domestic product (GDP) and waste production
was a major driving factor; key developments during this period included the
publication of the Memorandum on Prevention and Recycling and the introduction
of producer responsibility.

Processing organic waste into reusable products creates added value

During the 1990s, the Dutch Government began to tackle the environmental problems
associated with the recovery and disposal of waste with various pieces of legislation
such as the Waste Incinerators (Air Emissions) Decree, the Waste Substances
(Prohibition of Landfill) Decree, the Building Materials Decree, the BOOM Decree
(decree for quality and use of other organic fertilizers) and the Decree on
Waste Disposal at Landfills (under the Soil Protection Act).

The Dutch waste disposal practice of sending unsorted waste to landfill began
to decline with the imposition in 1982 of the so-called landfill ban; in its
place came regional waste incineration plants known in the Netherlands as AVIs.
In addition, a landfill tax was introduced in 1996 to make landfilling more
expensive than the preferred alternatives of prevention, reuse, material recovery,
recycling and incineration with energy recovery. Subsequent increases in the
landfill tax mean that the average charge for landfill is now around ¿115/tonne.

Waste has been collected in separate categories (organic garden and kitchen
waste, paper and carton, and residual waste fractions) in the Netherlands since
1993. However, some areas of cities are typically excluded from source-separated
waste collection mainly for logistical reasons (for example, in high-rise buildings,
portable wheeled containers are not convenient to use).

The Dutch National Waste Management Plan (LAP) has three main elements (policy
framework, sector plans and capacity plans) and aims to prevent and limit environmental
pressures through waste management by greater emphasis on prevention and recovery.
If recovery is necessary, the focus is on reuse and recycling; but, if this
does not work, the focus switches to waste as fuel (aiming to optimize the energy
content of non-reusuable waste).

Within this context, Orgaworld focuses on:

• source-separated organics (source-separated organics action plans)


• compost, bio-stimulators and fertilizers (BOOM Decree)


• high-calorific-value fuels (Air Emissions Act).

DUTCH AVIs HOLD BACK INNOVATION

According to Henk Kaskens, these relatively large-capacity AVIs were and still
are purpose-built for processing wastes with a low calorific value (they typically
have a specific energy content of around 9 MJ/kg). The overall efficiency of
these units is therefore low ¿ on average 20%¿25%. This compares unfavourably
with the 40% overall efficiency of a modern coal-fired plant or the around 50%
efficiency for a state-of-the-art gas-fired plant. In addition, AVI-type boilers
cannot cope with high-calorific-value solid waste fractions that often contain
chlorine (such wastes have an energy content of 13¿15 MJ/kg or even 20¿25 MJ/kg
for plastics), and this highly valuable solid fuel is exported to Germany.

`The AVI pay structure is entirely input-related,¿ Kaskens remarks further.
`Actual pay is based at Ex per tonne of waste material brought in for disposal.¿
In his view, a more `sensible¿ pay structure that takes into account quantifiable
potential outputs in terms of usable energy and/or reusable or newly engineered
products would be preferable. The major investment in state-owned AVIs means
that the Dutch Government is keen for them operate at full capacity and does
not always support new waste-processing methods if they would result in reduced
utilization of the AVIs. In addition, AVIs are paid twice for their services:
first for waste input (¿/tonne) and secondly for `renewable¿ energy produced
from the (50%) organic waste fractions (¿/kWh).

Kaskens argues that this focus on rewarding AVIs for waste intake and energy
produced puts a brake on innovation within the Dutch waste processing sector.
He is also critical of the widely practised cross-border trading in waste. `Orgaworld
disagrees with the common but essentially wasteful habit of moving huge quantities
of waste across the globe for centralized processing at random locations. In
addition, control on what is actually transported has proved complex ¿ not to
mention the enormous negative environmental impact due to the huge quantities
of transport energy involved with cross-border waste trading.¿

A second reason why Orgaworld prefers to build multiple, smaller decentralized
waste-processing installations is the much greater potential to reuse process
heat and to burn the methane gas released during anaerobic digestion, such
as in combined heat and power (CHP) installations. But to achieve these goals,
Kaskens concludes that `a completely new decentralized waste-processing infrastructure
needs to be developed.¿

PROCESS CHAINS

Although Orgaworld makes use of three different processes in its organic waste-processing
plants, all of which require largely the same physical infrastructure. All three
use solid waste that is not pre-treated and none result in leachate discharge.
The processes are:

• anaerobic digestion or fermentation in a BIOCEL (Figure 1)


• bio-stabilization (Figure 2)


• tunnel composting stabilization (Figure 3).

For many organic products, the process chain commences with anaerobic fermentation
followed by biological drying (composting) and/or bio-stabilization. Organic
wastes such as tree prunings do not produce biogas and go directly to the composting
section. The end products of the BIOCEL process are compost and energy, while
bio-stabilization produces solid fuels and solid residual materials for landfilling.
Tunnel composting outputs include compost, bio-stimulators and bio-fertilizers.

Fermentation of organic waste and similar industrial waste is a process performed
in a limited number of plants worldwide. Kaskens claims that `together with
our highly simple and robust process that is relatively insensitive to variations
in waste content, our rates are about 60% lower in terms of processing costs
in ¿/tonne waste input compared with AVIs.¿ For example, the energy demand
of the Orgaworld composting process is only 15 kWh/tonne compared with 40¿45
kWh/tonne for its earlier Spigot-type system, and up to 140 kWh/tonne for standard
state-of-the-art industry systems.

Compost-based products Compared with animal manure, nutrients in the organic matter of compost are released more steadily over a prolonged period of time. Compost produced from organic waste can also help reduce the consumption of peat by acting as a substitute in, for example, potting compost. Bio-stimulators Compost can be enriched with high concentrations of plant-stimulating organisms that improve the biological balance in the soil and that build in capacity to fight plant disease in agriculture. Orgapower¿s bio-stimulators are composts with a high concentration of micro-organisms that are claimed to enhance biodiversity and soil stabilization. According to Henk Kaskens from Orgaworld, a study by an independent institute has shown that the combination compost with bio-stimulators scores much better compared with a combination of mineral fertilizers and chemical pesticides and/or herbicides. Examples include the cultivation of strawberries, chrysanthemums, potatoes and trees. `However, one problem hampering the large-scale introduction of our compost enriched with bio-stimulators is that many agricultural experts are of the opinion that there are no alternatives to chemical herbicides and pesticides. And, as far as the remediation of contaminated soils is concerned, we have the know-how to manufacture custom made composts with micro-organisms that effectively ¿clean¿ these soils efficiently and for relatively low cost.¿ Bio-fertilizers No less than 5% of the world¿s total energy consumption is used for the production of mineral fertilizers. Chemical production of mineral nitrogen requires, for instance, 40 MJ/kg. Kaskens claims that Orgaworld can `produce bio-fertilizers with similar qualities and with the required nutrient mix of nitrogen, potassium and phosphate. The single difference between mineral fertilizers and Orgaworld¿s bio-fertilizers is a lower specific nutrient concentration in our product. As a consequence, the amount of fertilizer applied to agricultural land has to be higher. Of the required nutrients, organic waste from potato production contains a substantial concentration of potassium. Phosphate, by contrast, originates from dairy waste residues such as cheese and milk. Finally, we add organic-bound nitrogen during the tunnel composting process in a similar way to how a plant species like clover has its own built-in mechanism to make nitrogen to enable growth.¿ Orgaworld¿s bio-fertilizer is currently produced only on a pilot scale; while farmers like the concept in principle, they still need to be convinced in practice.

ANAEROBIC BIOCEL PROCESS

Orgaworld¿s modular design type BIOCEL in Lelystad was the first waste-processing
plant it acquired. The permitted annual capacity is 85,000 tonnes. The BIOCEL
plant consists of a large hall with multiple anaerobic fermentation cells in
a parallel two-row arrangement. Waste trucks arrive continuously at the entrance
to the hall. From this area, huge mechanized front-end loaders pick up the unsorted
waste for loading into the cells. The operators sit in air-conditioned, pressurized
cabins to provide a safe working environment free from bioaerosols. Huge doors
in the two opposing BIOCEL rows face each other for easier transport logistics,
and the spacious loading¿unloading transport area for the front-end loaders
is situated in between. Organic waste inputs are not limited to solid and semi-solid
materials, but also include liquids brought to the plant by tankers. Such liquids
are sprayed directly over the other material already present in the cells awaiting
anaerobic fermentation.

Once a BIOCEL is fully loaded, its airtight access door is closed. The next
step is to `drive out¿ the oxygen in the cell by pumping exhaust gases through
the waste until the correct oxygen-free conditions for the anaerobic digestion
process are achieved. These exhaust gases originate from two diesel generator
sets. (These are powered by methane, which is released continuously during the
anaerobic digestion process.)

The unsorted waste ranges from household kitchen waste to tree
cuttings and includes supermarket waste such as `expired¿ instant meals, plastic
and paper wrappings, and bread, cheese or sausages still wrapped in their packaging.
In addition, there are plastic-lined paper cartons, empty beer and soft drink
cans, bread and cakes, and citrus fruit skins.

A distinct feature of the Orgaworld approach is that no pre-sorting or pre-shredding
of the waste materials takes place before they are shovelled at random into
the BIOCEL for fermentation. Materials such as plastics, inert materials and
garden waste in the untreated waste provide the structure necessary to allow
leachate, which is spread continuously over the waste mass during the process,
to permeate it during the digestion process (the material is dried after digestion
¿ see below). Occasionally a shredder has to be used when the product wrappings
prove too strong for the `natural¿ mechanical damage that occurs during the
loading of the cells. Orgaworld¿s procedure for accepting waste from its customers
ensures that hazardous or unwanted wastes do not enter their processes. The
lack of machinery in the cells and tunnels means that packaging materials, metals
and inert materials can form part of the waste fractions; the product is sorted
at the end of the process (see below).

Waste is brought in continuously during the day from up to 100 km away and
originates from a wide consumer base including:

• municipalities


• the huge Albert Hein food retail chain


• other waste companies


• food, paper and wood industries.

There is no pre-sorting or pre-shredding of the organics before fermentation

Henk Kaskens comments: `Orgaworld is even permitted under the stringent waste
destruction rules of Albert Hein to process meat products by means of anaerobic
fermentation in the BIOCEL. Anaerobic fermentation itself is a relatively cheap
process that can be controlled well, provided material handling is kept simple
and robust. When we acquired the BIOCEL plant in 2000, it had been in trial
operation for about three years. The previous owner, a huge engineering consultancy,
also performed the in-house design and plant construction. The installation
was initially equipped with a number of sophisticated mechanical systems such
as shredders and state-of-the-art washing plant. This design philosophy fitted
into an industry trend but resulted at the same time in a highly unacceptable
need for maintenance, and the installation suffered from frequent breakdowns.
And as waste processing for third parties is always based on contracts, this
heavy demand for maintenance and frequent breakdowns ate away the profits to
be made.¿

Orgaworld¿s other plants All five Orgaworld plants, including the two in Lelystad, are certified according to the latest standards for quality, safety and environmental protection. The other three units are:a tunnel composting plant at Beek en Donk in the municipality of Laarbeek. In the tunnels, a wide range of organic waste can be processed under conditioned circumstances. The plant¿s licensed capacity is 35,000 tonnes/year. The plant not only produces compost but also fossil-fuel substitutes and bio-stimulators. A fully enclosed aerobic composting plant in the city of Drachten, which has a processing capacity of 44,000 tonnes/year. In addition to processing organic household waste, the environmental permit allows the processing of organic waste in a wider sense. Liquid materials containing organic waste are being processed in a fermentation plant at Elsendorp in the Gemert municipality. The main purpose of this plant is to produce more than 2.7 million kWh/year of `green¿ electricity. A new bio-stabilization plant is under construction in the city of Nijmegen, and an anaerobic fermentation plant is being planned in the city of Groningen.

He adds that the combination of waste materials and process water is a contradiction
in itself. When water is fed into the process, all kinds of potential problems
are created in the process chain. For instance, volume and weight are added,
the need for washing stages increases, and sieving becomes compulsory. All these
additional steps require electricity and heat energy, and therefore add to the
cost. Kaskens says: `A key problem was, for instance, that no one was interested
in buying plastic fractions that were contaminated with sand and dirt. On top
of that, aggressive micro-organisms and solid fractions such as sand and dust
particles are a disaster for rotating or otherwise moving mechanical systems.
That is what our years of experience in the waste processing industry had taught
us. In our view, the key is dry processing of waste based on anaerobic fermentation
and as few as possible pre-processing steps. The first thing we did after acquiring
the BIOCEL was to dismantle all the critical mechanical systems as part of a
major renovation effort by our own specialists.¿

The anaerobic digestion process currently takes three weeks. The acceleration
of the fermentation process achieved by Orgaworld is a result of knowledge developed
in-house, with a focus on microbiological research. Kaskens believes that an
extensive understanding of processes and an in-depth knowledge of all the matter
and materials involved are essential. `We have also invested heavily into selecting
those micro-organisms that provide optimal contributions to the anaerobic digestion
process.¿

Another key area of research is the creation of closely monitored homogeneous
temperature conditions in the BIOCEL in combination with high-tech process control.
The latter is achieved by precision-controlled aeration through the material
in the cell by means of an advanced patented aeration system. This technology
was developed in-house and is continuously refined. It is also used to maintain
an almost constant vertical temperature gradient in the composting and bio-stabilization
tunnels.

Biological drying

After the anaerobic digestion process is complete, the next step is biological
drying (or composting) of the digestate in a tunnel-type drying area near the
BIOCEL hall (Figure 1). Biological drying is an exothermal aerobic process whereby
a large quantity of low-temperature heat is released. So much internal heat
is generated during the microbiological conversion processes that almost all
the water in the waste mixture is evaporated. As a result, hardly any addition
of external heat is necessary and a dry matter content of up to 95% can be achieved
for the end-product compost, which is close to marketable quality. The process
is performed by Orgaworld both as post-composting phase after digestion and
as a separate, independent process (Figure 3).

The internal heat alone gives the compost a dry matter content of up to 95%

Sieving

Sieving follows at the end of the process stages and once both anaerobic digestion
and composting are complete. Plastic, metal, paper and glass fractions are physically
separated from the near-marketable product during sieving. The aim is to keep
plastic and paper fractions as pure and clean as possible. These are transported
to Germany as a high-calorific-value fuel source (such as briquettes, pellets
or fluff) for use in gasification plants or as a secondary fuel fed into coal-fired
plants. Combustion of these fuels takes place with a much higher efficiency
compared with burning relatively `wet¿ fractions in an incineration plant.

ENERGY PRODUCTION

`Optimizing biogas production is not a primary BIOCEL process objective,¿ says
Henk Kaskens. `We are happy with any quantity of gas that fits into an optimized
waste-processing solution. The biogas is used to power one or both gas engines,
depending on methane production. We produce about 3 million kWh/year of green
electricity, based on our current 35,000 tonnes waste input. One third of this
volume is consumed internally. Actual gas production depends mainly on the type
of waste material fed into the cells. During the summer period, gas production
is generally higher due a larger supply of source-separated organics being brought
in.¿

`All electricity produced is sold to the grid and some of the heat produced
by the engines is fed back into the anaerobic digestion process. We do not have
a gas storage facility near the BIOCEL, but we are considering investing in
temporary storage as it has become more economic in the liberalized energy market
to sell electricity only at times of peak demand. With our planned expansion
to 85,000 tonnes/year of operational capacity by 2006, the plant will produce
over 10 million kWh/year of green electricity. However, we expect our internal
consumption to remain largely unchanged, which implies that a larger quantity
can be sold externally.¿

COMPOST AND CARBON

At the BIOCEL plant in Lelystad, Orgaworld maintains limited storage of compost
that finds a ready market with farmers in the region. These farmers mainly use
the compost mixed with mechanically crushed wood fibres (sold through the company¿s
Orgapower subsidiary) for soil enrichment and improved water-holding capacity.

The heat generated in the biological process results in a high dry matter content in the final compost	Organic waste after the tunnel composting proces

Adding compost to the soil increases the stable organic matter content essential
to healthy biological soil activity. An additional advantage is that plant residues
that have been processed into compost are restored to the soil, the place where
they were once formed. Henk Kaskens comments: `During the past decades, the
organic matter (humus) content of agricultural land in industrialized countries
has been reduced by percentage points. Organic matter has a high carbon content,
which makes these soils a formidable carbon sink by enriching it year after
year with organic compost.

Investigation into co-firing of dried grass from road verges in coal-fired power plants Each year, huge quantities of grass are harvested from the road verges and embankments alongside city streets, highways and other civil engineering structures. This grass is often contaminated with heavy metals and other impurities and is therefore not always suitable as a raw material for compost for sale to farmers to improve soil. A study carried out by Orgaworld found that biological drying of mowed grass from roadside verges, and the subsequent grinding and pressing of the dried material into pallets, involve considerable energy consumption. However, a combination of drying, grinding and direct injection of the dried grass into the flame of a combustion plant proved a superior alternative. In a trial project, dried grass is being transported by truck (with a `suction blow¿-type trailer) to a coal-fired power plant in the Netherlands for secondary combustion. If the trial proves successful, a problematic source of organic waste would have been turned into a useful source of energy (electricity and sometimes also heat generation).

 

When the same quantity of organic waste is incinerated, the process carbon
is released immediately into the atmosphere and converted into carbon dioxide
¿ the main contributing factor to the greenhouse effect. The European Commission
has calculated that the total net emission of CO₂ could be fully
compensated in Europe if 0.1% of organic matter content were added to agricultural
soils each year. By continuing this suggested practice for several decades,
precious time can be bought to develop sustainable alternatives for our current
dependency on burning fossil fuels.¿

Eize de Vries is a freelance environmental journalist
based in the Netherlands. e-mail: wmw@jxj.com

For more information on Orgaworld, visit www.orgaworld.nl
or contact Ward Janssens at w.janssens@orgaworld.nl

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