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Livscyklusvurdering af 3 typer metalmaling
3. Summary
This report contains an inventory and an assessment of environmental impacts and
occupational health impacts at manufacturing, use and end disposal of a powdered paint, a
solvent based paint and a water based paint.
Paints with a specific recipe have not been chosen. On the contrary, average paints
were selected, where the "recipe" consists of an average of all recipes produced
for each of the 3 main types over 1 year, at the factory Technos Schou A/S.
Manufacturing phase
The inventory of the environmental impact in the manufacturing phase is based on an
environmental screening of TEKNOS SCHOU A/S made in the period from January 23, 1995 till
February 6, 1996.
As the environmental data from this screening are allocated to processes connected to
the manufacturing of the 3 types of paint, they can be converted to environmental impact
per each tonne of product. Environmental impacts, such as consumption of electricity for
lighting and administration, are allocated on the 3 types of paint according to the value
of the product.
Utility phase
As the examined paints are all hardened in an oven, the environmental impact in the
utility phase will primarily be impacts from the painting process, as drying in the oven
ensures that no volatility of solvents will follow when the painted product is being used.
The inventory of the environmental impact from the painting process has been made by
asking various producers of equipment for spray-painting and kiln-drying for information
concerning energy consumption and waste percentages. Furthermore, a calculation of
volatility of solvents and a calculation of the energy consumption for heating the
substitution air at the ventilation has been done.
Disposal phase
The paints from TEKNOS SCHOU A/S are primarely used on Danish products of metal which
are disposed to local product dealers (schredning) and from here to Staalvalsevaerket in
Frederiksvaerk (remelting). Some products are also disposed with normal waste for either
incineration or deposit.
The report discloses a plausible distribution in percentages of the ways of disposal in
Denmark. Subject to an assessment of the quantity of paint ending up as gas emissions,
incineration ash, volume waste and chemical waste, respectively, an estimation of the
destiny of paints at schredning, remelting, incineration and deposit respectively, of
painted metal products has been made.
In order to decide the content of carbon, nitrogen, chlorine, sulphur and heavy metals,
the gas emissions have further been specified by means of analysing of the paint.
Environmental assessment of manuafacturing, use and disposal
The environmental assessment of the collected data has been made by means of a demo
version of UMIPTOOL. This is an electronic tool developed in connection with the
UMIP-project.
The assessment includes:
- classification of emissions according to type of environmental effect (greenhouse
effect, erosion of the ozone layer, eutrophication, etc.),
- normalisation of the classified emissions compared to the Danish average figures, hereby
recalculating the emissions to person equivalents
and finally,
- weighting, where a factor of weight for the normalised emissions according to
environmental importance is subject to a multiplication.
The assessment has been made per tonne paint and per functional unit. The functional
unit has been chosen as:
"The quantity of paint needed to cover 1m2 of metal plate"
which corresponds to approx. 135 g. of powdered paint, 90 g of solvent based paint and
90 g of water based paint.
The durability of the painted metal plates are not included in the functional unit,
because TEKNOS SCHOU A/S has not been able to identify differences in durability of the
painted metal sufaces when the mentioned thickness of paint layers are used.
The result of the environmental assessment is shown in chapter 8. For the 3 examined
paints the following areas are given the highest priority:
Processes:
Reduction of the quantity of hazardous waste and the consumption of electricity in
the utility phase for paints based on solvents and on water.
Substances:
Reduction/substitution of xylene in solvent based paint and TGIC-hardener in
powdered paint.
Plan of action
In the project a detailed plan of action has not been made. A list of the environmental
topics which are to be worked with, to solve some of the problems mentioned above, has
been made. The topics are:
- focus on the raw materials, which ought to be replaced
- minimisation of environmental impact in the utility phase (reduction of the content of
solvents and of substances ending up as chemical waste
- manufacturing of kiln-dried paints with a small consumption of energy
- focus on reuse of paint
Only the first subject are selected to be further elaborated in this report, i.e.
replacement of hazardous raw materials.
Screening of raw materials
Due to the big number of raw materials (20 - 40 for each type of paint ), it has been
necessary to select the most important from an environmental point of view. This selection
is based on evaluation of:
- a weight criterion
- Overall materials- and energy consumption, and emission of hazardous substances to air
or water in manufacturing the raw material
- Environmental problems in manufacturing, use and disposal of the paint caused by the raw
material
The screening disclosed that the essential raw materials, in an environmental point of
view, were the solvent xylene, the hardener TGIC and the white pigment TiO2.
Xylene
It is possible to substitute xylene in the solvent based paints with e.g. paraffin's or
other hydrocarbons, but they are much more expensive (a factor 10) and will impose other
problems with occupational health e.g. Consequently, a more realistic alternative will be
to change to a total new painting system as e.g. water based paint or powdered paint,
which are exactly the alternatives investigated in this report. Thus it has been decided
not to do any further investigations concerning alternative solvents in this report.
TiO2
TiO2 is a supreme white pigment because of its refractive index and in real
world experience, there are no practical alternatives. However, TiO2 can be
manufactured by two alternative process routes called the sulphate process and the chloride
process which are compared in this report. Due to the very widespread use of TiO2,
there are a lot of investigations and data concerning environmental impacts through the
total life cycle of this substance. Apart from general literature from handbooks, data
from Buwal /8/, Tioxide /17/ og KRONOS TITAN /22/ have mostly been used in this report.
By comparing the environmental impacts during the whole life cycle of TiO2
it has not been possible to encounter any substantial differences in the two process
routes. Compared to the chloride process the sulphate process tends to cause higher
impacts. However, this is hidden by variations in the emission of small amounts of e.g.
mercury by both processes.
TGIC-hardener
TGIC is today widely used as hardener in manufacturing powdered paints. Unfortunately
TGIC has some problematic occupational health characteristics, as e.g. allergen effects.
According to EU-rules for chemicals, TGIC must be marked with the symbol T (toxic) as of
May 31 1998.
Therefore, Technos Schou A/S wants to substitute TGIC with a more environmentally
correct substance and the most promising candidate pt. is b -hydroxyalkylamide. These two
substances are the ones investigated and compared in this report.
Environmental assessment of alternative rawmaterials
As no final LCA's have been made in advance for hardeners as it was the case for TiO2,
it has been necessary to make a detailed inventory of the manufacturing processes,
chemical reactions, resource consumption and emissions for each step back to extraction of
the primary raw materials.
Comparing the environmental impacts by substituting TGIC with b -hydroxyalkylamide
showed both improvements and recessions:
Improvements:
- Reduction of occupational health impacts (related to TGIC as allergen and toxic
substance)
- Classification of powder waste are changed from hazardous waste to common waste, under
the assumption that all TGIC in powder paints are substituted with b -hydroxyalkylamid.
- Reduction of emissions of chlorine compounds by disposal of powdered paints
Recessions:
- Small increases in consumption of resources (natural gas, oil and coal)
- Small increases in greenhouse effects (caused by emission of N2O)
Due to the possibilities to abate the emission of N2O it is in total
evaluated as an improvement to substitute TGIC with b -hydroxyalkylamide. Removal of
T-marked substances are additionally a high priority subject at TEKNOS SCHOU A/S.
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