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TWENTY million tonnes of household refuse end up in Britain’s dustbins
every year. With a good recycling scheme, Britain should be able to recover
just over 40 per cent of this total. In practice, however, this figure is
likely to be nearer 30 per cent, and there are good reasons why we need
to find better ways of disposing of the rest.

Unlike many other countries, Britain disposes of about 90 per cent of
its waste in dumps or ‘landfill sites’. Switzerland, by comparison, disposes
of only 20 per cent in this way; Japan and Denmark 30 per cent; France and
Belgium 35 per cent; Italy 60 per cent and West Germany 65 per cent. One
reason for these differences is that during the 1970s, Britain’s low transport
costs and plentiful landfill sites close to urban areas combined to make
landfill a cheap option. Now this situation is changing: transport costs
rose steadily throughout the 1980s, and some cities are running out of suitable
sites for disposing of their waste.

London sends most of its 3 million tonnes of domestic waste to landfills
in Kent and Essex. But SERPLAN, a planning body for London borough councils
and county and district councils in southeast Britain, predicts that by
2000 all the available space for domestic refuse in Essex, Kent, East Sussex
and Surrey will be used up. Already, some of London’s waste travels 80 kilometres
away by rail to Bedfordshire and Buckinghamshire. Here, there is no shortage
of space, but rail transport is expensive, bringing the total costs of disposal
up to as much as Pounds sterling 20 per tonne.

Increasingly, landfill sites are owned and managed by private contractors.
Shanks & McEwan is one of the largest in Britain, handling up to a million
tonnes of domestic refuse each year. According to Chris Cox, special projects
manager for their southern area, the cost of disposing of domestic refuse
has doubled over the past three years and he expects it to continue to increase
by 15 to 30 per cent a year.

Another reason for the increase in handling costs is the pressure on
contractors to improve site standards. Last year licences were upgraded
and waste disposal companies must now do more to overcome two potentially
serious environmental problems created by landfill: leachate and landfill
gas.

Leachate is the liquid that oozes out of landfilled waste. The leachate
from domestic waste contains partly decomposed organic material and microbes,
including disease-causing bacteria and it can be an uncontrolled source
of landfill gas outside the landfill site if it is allowed to disperse.
Landfill gas is a potentially explosive mixture consisting of two parts
methane and one part carbon dioxide, produced by the decomposition of organic
material.

Lack of monitoring

Although the better sites control both leachate and landfill gas, they
are still a cause for concern: in a recent survey of 100 representative
landfill sites in Britain, researchers from the Environmental Safety Centre
at Harwell found that almost a third did not monitor levels of gas or leachate.
A further 10 per cent were aware of problems but had taken no action (This
Week, 12 May).

Most recycling schemes in Britain do nothing to alleviate these environmental
problems because they take out only the inert fraction of waste: glass,
plastics and metals. If anything, they make things worse because the residue
is even richer in the putrescible materials that produce both leachate and
landfill gas. But recycling could make an important contribution to various
alternatives to landfill, and as costs rise and sites become scarcer, these
are becoming increasingly attractive.

John Barton is head of the materials recovery section at Warren Spring
Laboratory, an agency of the Department of Trade and Industry. Barton and
his team are monitoring an integrated scheme for recovering both materials
and energy from domestic refuse at the Byker Reclamation Plant in Newcastle
upon Tyne. ‘Domestic refuse is probably the most complex mixture of materials
ever dealt with on an industrial scale,’ says Barton. ‘The equipment for
processing it must be robust and simple – once it is segregated, technology
can play a role.’ He compares it to the breaking down of petroleum into
its many useful components.

Researchers at Byker have pioneered a mechanical sorting system in which
the mixed refuse passes initially through a revolving barrel that separates
it according to size. The barrel has a mesh that allows through ‘fines’
of less than 50 millimetres. The rest is then pulverised and further sorted
by size and density. An overhead magnet removes ferrous metals for detinning,
leaving a mixture of newspaper, cardboard, plastics and a small amount of
wood, textiles, metal and leather. This mixture can be pressed, dried, and
formed into fuel pellets. The idea of turning refuse into fuel is not new;
refuse-derived fuel (RDF) first appeared in Britain back in 1975. But pilot
schemes set up in the 1980s at Byker, Doncaster and Eastbourne to make RDF
pellets as a replacement for coal met with little success. Engineers found
that RDF caused corrosion and the build-up of deposits on some types of
boiler. These technical problems, combined with low oil and gas prices and
the unreliable quality of the pellets, meant that they were difficult to
sell.

Early RDF plants pulverised the waste before separating it, so the fuel
was often contaminated and of poor quality. Barton and his colleagues say
that they have now solved many of these problems. Their sorting system is
the result of many years of work on ways to maximise the fuel’s energy value.
Fuel pellets from Byker have around one-third of the weight of the original
refuse but a heating value of 18.5 megajoules per kilogram. A kilogram of
coal yields about 28 megajoules. The pellets have different physical and
chemical properties to coal; they burn faster, and produce more ash and
volatiles, for example. But conventional and relatively cheap solid-fuel
boilers can be converted to burn them, and despite their unpopularity in
Britain, there are large-scale RDF plants in continental Europe and the
US.

The biggest problem facing RDF in Britain, however, is likely to be
new legislation by the European Commission (EC) on emissions due to come
into effect in 1996. RDF meets current regulations in Britain but it will
not meet the new European standards for hydrogen chloride and heavy metals,
especially cadmium, unless boilers are fitted with flue gas scrubbers and
filters. This could be prohibitively expensive for the small-scale industrial
boilers that use this fuel.

One way round the problem may be to use the fuel at the point of production.
Isle of Wight County Council opted to build an RDF plant in the 1980s as
the solution to two pressing waste problems: shortage of landfill sites
and the high costs of transporting the waste to mainland Britain. The plant
was commissioned in January 1989, incorporating the latest separation technology,
and now produces 15 000 tonnes of good-quality fuel pellets per year (Technology,
12 November 1988). But variations in oil prices have affected sales of the
fuel and the council is considering whether to use it to generate electricity.
This became an economically attractive option last year with the privatisation
of electricity. As a result of the Electricity Act 1989, public suppliers
of electricity in England and Wales must obtain some of it from non-fossil
fuel sources. Small-scale producers of electricity (below 10 megawatts)
from non-fossil fuels are also paid a higher price for it than the normal
price paid for electricity from fossil fuels. The council is still awaiting
a decision from the government on its appli cation for a 2-megawatt generator.
But the situation is still far from clear: a few months ago the EC ruled
that the British government could only offer this help until the end of
1998, when electricity from non-fossil fuels must revert to a standard price.
The Department of Energy is still discussing this with the EC.

Modern plants for converting refuse into fuel have other advantages.
Apart from separating materials such as metals and glass for recycling,
much of the refuse rejected from the fuel production line makes equally
useful by-products. At the Byker plant, for example, 35 per cent of the
original refuse goes through the first 50 millimetre mesh as fines of mostly
putrescibles, glass and dirt. Paul Bardos, a microbiologist at Warren Spring
Laboratory, is monitoring a pilot scheme at Byker that turns these fines
into 15 tonnes of compost a week. The composting process, which converts
the organic waste into stable humus, together with water, carbon dioxide,
inorganic ions and heat, is brought about by microorganisms naturally present
in the waste. At Byker they use an ‘aerated static pile’ in which air is
blown through compostable material that is carefully maintained at the correct
levels of moisture and temperature. (More tradi tional methods of composting
lay out the material in rows, turning it at intervals to aerate it.)

Surprisingly, the microbiology of composting is poorly understood. The
process occurs in two stages. After the first stage (50 to 60 Degree C),
the compost still contains complex biochemical intermediates that are toxic
to plants. Bardos and his colleagues favour a temperature of 55 Degree C
as the best compromise between killing disease-causing bacteria and optimising
the decomposition, but many commercial plants operate at higher temperatures.
During the second, lower-temperature stage (15 to 35 Degree C), microorganisms
break down the toxic intermediates and stabilise the compost. After 3 to
4 weeks the product is screened to remove glass and a small amount of grit;
what is left smells and looks very similar to the peat-based compost on
sale at garden centres all over Britain. Byker is currently the only plant
in Britain producing compost from domestic waste. The compost is being stored
and will be used later in autumn for tree planting.

As a solution to the problems of leachate and landfill gas, composting
is ideal. Done properly, it stabilises organic compounds so that they do
not decompose further and kills disease-causing bacteria and weed seeds.
It also reduces the volume of waste.

Composting may turn out to have other advantages. Some researchers predict
that peat reserves in Britain will only last another 10 to 30 years, and
interest is growing in compost from refuse as a possible alternative. Compost
from refuse is not a fertiliser – any nitrogen it contains is released slowly
into the soil – but it has other useful properties. Stephen Norcliff, a
researcher in the Soil Science Department at the University of Reading,
is optimistic about developing compost to replace peat as a soil conditioner
to improve soil structure. Applied to the surface, it could also stop weeds
growing and conserve moisture. ‘Compost has many of the properties of peat
– it is a good organic base and holds water,’ says Norcliff.

There are some problems, however. One is economics: the return on a
tonne of compost is about the same as for a tonne of raw refuse (Pounds
sterling 10 to Pounds sterling 20). Potentially more serious is that as
composting reduces the volume of refuse, any heavy metals in it become more
concentrated. One source of these heavy metals is batteries, which are likely
to end up in the ‘fines’. Batteries make up between 0.1 and 0.3 per cent
of domestic refuse and are difficult to separate mechanically because they
are made of a mixture of materials. More important still are house dust,
metal shards, wine bottle tops, paints and the materials added to plastics
to make them flexible, which are difficult to remove either before or after
composting.

Concern over the heavy-metal content of compost has restricted its use
in parts of Europe. There are no EC standards for either compost or peat
and some countries have adopted their own. These vary widely, with the Netherlands,
West Germany and Denmark demanding the most stringent. Other countries,
such as France and Italy, suffer from the soil erosion that accompanies
Mediterranean climates; they value compost for its ability to replenish
lost organic matter in the soil and are therefore prepared to accept higher
levels of heavy metals.

Another problem is the high concentration of sodium, calcium and potassium
ions in the compost. Put directly onto seedlings, such a high level of mineral
nutrients can kill them. According to Joe Lopez-Real, a microbiologist at
Wye College, part of the University of London, this problem is easily solved
by watering the compost or mixing it with peat. But it is still an area
for concern.

Some county councils in Britain, notably Leicestershire, have experimented
with composting in the past, but a combination of poor marketing and problems
with the high glass content of their compost brought them limited success.
Bardos thinks that in Britain there is also a general lack of understanding
of fundamental principles: ‘Full-scale plants were built before they were
properly tried and tested.’

Now a British company, Secondary Resources, hopes to make a commercial
success of a system for recycling domestic refuse. The company is part of
a joint venture with Birmingham City Council: the council pays for collection
of the waste and the company recovers metals and converts most of the rest
to RDF and compost, as a direct alternative to landfill. Profits from selling
the reclaimed metals, RDF and compost offset the council’s costs. Tony Manser,
technical and operations director at their Castle Bromwich plant, said:
‘the target we expect to achieve over the next few months is 130 000 tonnes
(of refuse) per year.’ The company took over an old RDF plant from the council
in March 1989 and have just completed a Pounds sterling 3.5 million modification
to it. They now hope to produce around 25 000 to 30 000 tonnes of fuel to
sell to industries in the West Midlands.

Manser was noncommittal about costs: ‘It’s too early to say. At the
moment we would charge the local authority about the same as for landfill,
but the picture is changing – landfill costs are going up, by 48 per cent
in the last year in Birmingham.’

Compost heads for the market

Secondary Resources believes that it has solved many of the problems
associated with refuse-derived compost, by pre-screening the refuse in a
series of steps to remove glass, metals, most film plastics and batteries.
The company is patenting its extraction process for glass and batteries.
Of the residue, paper and plastics go into the RDF stream, and putrescibles
are removed by flotation and composted. Composting takes place inside a
closed vessel at around 60 Degree C, a method which the company hopes will
guarantee a consistent quality of compost. One problem with ‘closed vessel’
systems is ensuring that all the material inside is properly aerated. After
about a month the compost is mature. Then it is re-screened to remove more
plastics.

This compost, or ‘humus’, will be tested by potential customers, including
Kew, Chelsea Physic Garden, Birmingham City Council and various landscape
architects, as well as by the Ministry of Agriculture, Fisheries and Food,
Imperial College and Reading Soil Services. According to John Mullet, the
company’s science director, the heavy-metal content of the compost is within
a few parts per million of the West German standard for sewage sludge, and
better than some peat-based composts on sale in Britain. If the tests are
successful, the company intends to produce 40 000 to 50 000 tonnes of compost
in the next year and supply it as a raw material to major peat-blending
companies – some of whom own peat bogs.

A different way of recycling refuse is to consider it as a source of
energy, rather than materials. This approach is popular in Europe, where
incineration has the added advantage of reducing the volume of rubbish for
landfill by as much as 90 per cent. The heat content of ‘raw’ rubbish has
been increasing steadily for several decades, as its paper and plastics
content has increased. A kilogram of raw refuse burns to give about 11 megajoules
of energy, so the domestic waste produced in Britain each year is equivalent
to more than 6 million tonnes of good quality coal.

Although Britain pioneered the incineration of household waste a century
ago, we now incinerate only about 8 per cent, well behind most other countries.
Switzerland incinerates 80 per cent, Japan 68 per cent, Sweden 50 per cent,
the Netherlands 40 per cent, West Germany 35 per cent, France 36 per cent
and Austria 18 per cent. In the US only 10 per cent is incinerated but large
incineration schemes soon to be introduced there will increase this to 19
per cent by 1992.

Incinerators can recover the energy in refuse in two ways: by converting
it to heat and power and, more simply, by generating electricity. The technology
for both is already well developed in continental Europe, where many incinerators
supply district heating schemes. Combined with recycling of some materials,
this should be a good option to replace landfill in urban areas: to be economic,
an incinerator needs to handle around 200 000 to 250 000 tonnes of refuse
a year.

But in Britain there are severe problems. In 1989 there were 36 domestic
incineration plants operating in England and Scotland. They were built 10
to 20 years ago and none of them currently meets new European directives
on emissions, adopted in June 1989 and due to come into effect in 1996.
Current legislation regulates chimney height, grit and dust emissions. The
new directives set maximum limits for emissions of hydrochloric and hydrofluoric
acid, sulphur dioxide, heavy metals (lead, chromium, copper, manganese,
nickel, arsenic, cadmium and mercury) and total dust, as well as the carbon
and carbon monoxide content of flue gases for both existing and new plants.
They also specify at what temperature and for how long gases should be burnt,
to make sure dioxins are destroyed. The best of Britain’s ageing incinerators
are at Edmonton in North London, Coventry and Sheffield. These are early
versions of designs that are now in widespread use in Europe and they are
the only ones that can be updated fairly easily to meet the European directives.
The extra cost of adding gas scrubbers to reduce hydrogen chloride emissions
will increase the cost of incinerating a tonne of rubbish to around Pounds
sterling 30. Many of the other incinerators will have to be shut down.

Byrom Lees, senior fellow of the Institute of Energy and a fuel technology
consultant, thinks that Britain urgently needs a crash programme to introduce
new incinerator technology. He sees pre-processing the waste into fuel as
‘an expensive and unnecessary step’. But he is pessimistic about the ability
of private contractors to provide the necessary investment over the next
10 to 15 years. He cites the Edmonton incinerator as a typical example.
Installed in 1970 to the latest designs, it could turn 375 000 tonnes of
waste per year into power. But the Pounds sterling 12 million installation
cost was partly subsidised by the Greater London Council. Today, the installation
costs for even a 150 000 tonne plant would probably be nearer Pounds sterling
30 million.

Power in the city

The last incinerators in Britain to be built with facilities for recovering
energy from waste are those at Sheffield, Coventry and Nottingham; all three
date from the 1970s. Three years ago, following a consultant’s report on
waste management to the London boroughs of Greenwich, Lewisham and Southwark,
a consortium was set up which now intends to build a mass-burn incinerator
in Lewisham to convert refuse into heat and power. If the consortium is
successful in raising enough capital, this will be the first new domestic
incinerator to be built in Britain since 1976. It meets the new European
directives on emissions (these apply now for new plants) and will burn 400
000 tonnes of refuse a year, supplied by the three London boroughs. The
fee paid by the boroughs for disposal of the refuse must compete with that
charged by landfill operators. The plant will produce about 30 megawatts
of electricity for sale to the London Electricity Board (LEB) and enough
heat and hot water for 10 000 homes in Southwark (currently supplied by
small central boilers).

The incinerator is based on the Martin grate system developed in West
Germany and other countries over the past 30 years and has two waste streams,
each handling 29 tonnes per hour. But again, there are problems with the
1998 time limit imposed on the higher ‘premium’ price paid to electricity
obtained from non-fossil fuels. Initially, the proposal was for a 20-year
contract, to cover the return on the Pounds sterling 70 million investment:
now the plant operators can only contract to supply electricity to the LEB
at a fixed price until December 1998, and the plant will not even be built
until 1993.

Two other similar schemes for turning London’s waste into energy are
now planned. In August, Cory Environmental announced that it is investigating
the feasibility of an 80 to 100 megawatt power station on the Thames, which
would incinerate up to one-third of the capital’s domestic refuse. A small
private company, Capital Power and Waste, has applied to use part of the
redundant Battersea power station to burn 500 000 tonnes of domestic waste
per year to generate an as-yet unspecified amount of electricity.

Environmentalists have a difficult task weighing up the options for
waste. Not only do experts disagree about what constitutes the best technology,
but no one has yet worked out the relative costs and benefits, either economic
or environmental. Some researchers think that what Britain needs now is
an economic/environmental audit to do just that. Without government support
for such a survey, the government’s commitment to recycling, for either
materials or energy, begins to look less than wholehearted.

* * *

The biggest compost heaps in the world

COMPOSTING is much more popular in the rest of Europe and the US than
in Britain. In Duisburg, West Germany, a 31-year old plant composts 100
tonnes of domestic waste a day; a plant at Bad Kreuznach handles twice this
amount. In some parts of West Germany, however, concern over toxic metal
contamination has limited compost from mixed refuse to use as a filler and
in sound reduction barriers on motorways.

Many European composting plants, such as the one at Frederikssund in
Denmark, compost a mixture of refuse and sewage sludge. In the US, pressure
to find alternative ways of disposing of sewage sludge has also encouraged
the development of such mixed plants. Portland in Oregon may soon have the
biggest solid waste composting plant in the US. It is being built to handle
800 tonnes of waste a day in conjunction with a recycling scheme for metals,
plastics, paper and glass. There are at least three composting plants in
Egypt.

In Europe, early systems for composting refuse were based on mechanical
separation and the compost often contained impurities. More recently, there
has been a strong drive towards improving its quality. The best way is by
householders separating compostable material, such as food scraps and vegetable
peelings, from non-compostable material, such as vacuum cleaner bags, disposable
nappies, sanitary towels and shoes.

In Munich, a one-year scheme is being set up in which 40 000 households
will be given a ‘biobin’ that is emptied every fortnight.

Munich council expects to divert about a third (50 000 tonnes per year)
of the waste going to two incinerators and landfill sites in this way, with
sales of the compost offsetting costs.

The only such scheme in Britain so far is Wyecycle, set up in May by
Joe Lopez-Real, a lecturer in microbiology at Wye College (part of the University
of London) as an extension to an existing recycling scheme. Almost 200 households
in Wye now separate their compostables into a strong paper bag for weekly
collection and composting.