3. Notes on the analysis and evaluation of environmental impacts
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3.1 Emission-limiting requirements
Two types of requirement are imposed on sugar factories: general and special. The provisions regarding general regulations to limit emissions contain:
- emission values, which current technology can keep to admissible levels,
- emission-limiting requirements conforming to the state of the art,
- other requirements to protect against harmful environmental impacts by air pollution and
- processes for determining the emissions.
The following general requirements are imposed:
- reduction in the quantity of waste gas by enclosing plant components,
- registration of waste gas flows,
- circulating air management and process optimisation through more efficient use of waste heat,
- waste gases must be released so that they are freely discharged without obstruction in the general airstream,
- chimneys should be at least 10 m above the ground and project 3 m above the roof ridge, but should be no more than twice the height of the building,
- in the field of wastewater treatment, including lagoons, anaerobic degradation shall be eliminated by technical or structural measures as far as possible.
The special requirements (e.g. in Germany in accordance with the TA-Luft [Technical Instructions on Air Quality Control]):
- the drum inlet temperature in sugar beet slice drying plants must not exceed 750°C or equivalent measures to reduce odours must be applied,
- dust emissions in the damp waste gas must not exceed 75 mg/m3(f),
- where solid or liquid fuels are used, the sulphur content by weight must not exceed 1 % in the case of solid fuels related to a net calorific value of 29.3 MJ/kg, or equivalent waste gas purification must be carried out.
A crucial factor in all emission considerations is the emission load resulting from the quantity of waste gas discharged from the chimney, multiplied by the pollutant concentration. This concerns primarily the load from sulphur, nitrogen oxide, carbon monoxide and dust.
The following emission limits apply to furnace installations with a furnace heat output of < 50 MW:
Source: TA-Luft [Technical Instructions on Air Quality Control]
The emission values relate to an oxygen content by volume in the waste gas of 3% for liquid and gaseous fuels. In the case of solid fuel, 7% applies where coal is used and 11% applies where wood is used.
Flue ash and soot are the main air pollutants where bagasse is used as fuel, but flue gases from bagasse do not contain any toxic substances. Where fuel oil is used in the cane sugar industry, a sulphur content of 0.5 to 1.0 % by weight in the fuel oil is permissible.
The main parameter of any biological treatment and in any watercourse is the biochemical oxygen demand (BOD). This is the quantity of oxygen in mg/l which is consumed by microorganisms at 20°C within a degradation time of five days. The chemical oxygen demand (COD), on the other hand, is the standard for the content of oxidisable substances found in water, i.e. the method covers not only biologically active substances but also inert organic compounds. It is essential to use the COD method (evidence provided using potassium permanganate or potassium bichromate) as a fast method of determining the level of water pollution.
In its guidelines for the cane sugar industry, the World Bank takes the view that three parameters are of fundamental importance when it comes to assessing sugar factory wastewater pollution with biodegradable substances and their impact on the environment:
· BOD5 for determining the oxygen-consuming organic material;
· TSS (total suspended solids mg/l) for establishing the total quantity of suspended matter (primarily inorganic substances from cane and beet washing water);
· pH as extreme pH changes are harmful to water fauna.
The minimum requirements regarding the pollution levels in wastewater to be released into bodies of water are based on the treatment processes normally applied in the various industries and must conform to the state of the art.
For sugar production and associated industries (including alcohol and yeast production from molasses) the following minimum requirements are specified in Germany (source: (1)):
|A cm3/l random sample||COD mg/l mixed sample||BOD5 mg/l mixed sample||(TF) random sample|
|Seal and cond. water||0.3||60||--||30||--||--|
A = volume of suspended solids
TF = toxicity to fish, expressed as the minimum dilution factor of the wastewater at which all test fish survive under standardised conditions within 48 hours.
These values apply to random samples in the case of lagoons.
Due to local circumstances it may be necessary to limit other parameters for discharging into watercourses, e.g. temperature, pH, ammonia, chloride.
In the USA, the Environmental Protection Agency (EPA) has imposed limit values for cane sugar factories (raw sugar factories and refineries).
General limit values regarded as "best available technology economically achievable" (BATEA or BAT) are:
|Raw sugar factory||(kg/t cane)|
|White sugar factory||(only mixed condensate)||(kg/t raw syrup)|
|Liquid sugar factory||(only mixed condensate)||(kg/t raw syrup)|
|30-day||pH 6.0 - 6.9|
With regard to sugar factories, the noise immission guide values are (in Germany) 60 dB(A) in the daytime and 45 dB(A) at night. Cane sugar factories are generally located in the centre of the growing area, very rarely in the vicinity of sizeable residential areas. The design of factories is light and open (due to the climate); cane is received and conveyed to the mill in the open air (large quantities of dust generated).
Noise emissions can be restricted by structural and acoustic measures, with housings provided around sources of noise and soundproofing.
Where the noise from certain tasks or areas of the factory cannot be restricted or insulated, personnel shall be issued with appropriate individual protective gear.
These include, in particular, tipping and bagging plants, cane handling and roller extraction, washing plants for the raw material and the centrifuge station. In the workshop area, they include mainly work at rotary machines with a diameter > 500 mm, sheet metal processing machines and drilling and punching machines. The acoustic power level in these areas ranges from between 80 and 130 dB(A). At values of > 85 dB(A), individual protective gear (ear plugs, ear muffs) must be worn. With acoustic pressure levels of > 115 dB(A), the combined use of both items is recommended.
3.2 Technology for the reduction of emissions and emission monitoring
Measures to prevent damage due to atmospheric sulphur dioxide immissions in flue gases comprise the retention of SO2 in desulphurisation plants (e.g. absorption in lime milk) and the use of low-sulphur fuels. The installation of a scrubber before the chimney inlet has proved successful in reducing the emission load in waste gases. As well as its action on dust, this scrubbing operation achieves an SO2 separation of some 30%. If sludge from calcium carbonate precipitation is used as the washing liquid, pure gas dust concentrations of less than 75 mg/m3(f) are obtained. At the same time the SO2 emission is reduced by 60 to 70 %. "Calcium carbonate precipitation scrubbing" is therefore a particularly good dust and SO2 separation method as it does not pose any additional wastewater or residue problems.
Dust emissions occurring inside the sugar factory are reduced with scrubbers or fabric filters and the pure gas concentration is less than 20 mg/m3. Dust levels are kept low in the same way during further processing stages.
In the cane sugar industry, the generally high proportion of flue ash necessitates flue gas purification measures. Older furnace plants can be easily fitted with wet or dry separators (cyclones: approx. 96% effective, more investment- and maintenance-intensive than wet separators). The water requirement figures for wet separation are approx. 0.025 m3 water/25 m3 gas.
Emissions and the temperature in the waste gas from steam generation and slice drying are measured and monitored by integrated, continuously operating measuring instruments. In the cane sugar industry, portable, manually operated equipment (e.g. Orsat apparatus) is used mainly to determine, for example, oxygen, carbon dioxide and monoxide. If state-of-the-art waste gas purification systems are installed in new plants, and if dust emissions are below 75 mg/m3, daily measurements with a portable unit are adequate.
Any odour nuisance due to ammonia emissions is largely suppressed in advance by closed-circuit systems.
In principle lagoons should be fitted with additional aeration equipment, and aeration rollers have proved extremely successful here. They should not be located in the immediate vicinity of a factory or residential area (upwind).
A number of processes can be used to measure rate of discharge, e.g. measurement of flow rate with an impeller device and integration via the discharge cross section, or direct determination with a measuring weir.
The mixed samples taken for wastewater assessment are analysed for BOD5 according to DEV (source: (5)) and for sludge deposits, COD and toxicity to fish according to DIN. The EPA has specified the analysis methods for the cane sugar industry in "Methods of Chemical Analysis of Water and Wastes". In the case of lagoons, random samples are adequate in view of the low fluctuations over time of wastewater composition and the long retention times.
Control services and control mechanisms should be put in place to check that environmental provisions are observed, e.g. environmental protection consultants. Their task would also involve checking that environmental protection installations are in good working order and are regularly maintained, and they would also be responsible for personnel training and making personnel aware of environmental issues. Medical care should be provided inside the works and for the local population.
3.3 Limit values issued to protect health
Substances for which maximum workplace concentrations (MAK values) or technical approximate concentrations (TRK) apply in Germany: mg/m3 Application/source
Ammonia 35 - Raw material treatment, extraction, juice purification, juice concentration, lagoons;
Asbestos dust 0.025 - Heat insulation, filter aids (diatomaceous earth);
Lead 0.1 - Laboratory: lead acetate solution for the clarification of juice samples for polarisation analysis;
Calcium oxide 5 - Milk of lime manufacture: juice purification, juice neutralisation, wastewater treatment; lime burning;
Hydrogen chloride 7 - Evaporator station: cleaning with dilute hydrochloric acid to remove incrustations (calcium carbonate);
Formaldehyde 1.2 - Disinfectants: at places in the production area at risk from microorganisms, mainly extraction;
Hydrazine 0.13 - Anticorrosives for boiler feed water (chemical oxygen bonding with hydrazine hydrate);
Carbon dioxide 9000 - Juice purification (calcium carbonate precipitation); lime burning;
Sulphur dioxide 5 - Made from sulphur in sulphur furnaces, juice purification (calcium sulphite precipitation), acidification of the extraction water, waste gases where fossil fuels are used;
Hydrogen sulphide 15 - Raw material treatment, lagoons;
Dust (generally) 6 - Cane receipt and crushing, slice and sugar drying, sugar bagging; storage of excess bagasse.
Synthetic flocculants do not create dust or irritate the skin when handled, and do not constitute any toxicological hazard. Carcinogenic substances and substances which are suspected of having carcinogenic potential are: asbestos dust, alkali chromates and lead chromate (laboratory reagents), formaldehyde, hydrazine, fumes from VA welding.
The lethal dose (LD50) of a 39% formaldehyde solution is 800 mg/kg body weight (oral: rat); according to the working materials ordinance Arbeitsstoff-Verordnung classified as "low toxicity" and labelled with the hazard symbol R22 ("harmful if swallowed!) (necroses of the mouth, oesophagus, stomach).
Measures: in principle toxic chemicals must always to be kept sealed; the wearing of rubber gloves is recommended for analysis work; vessels and instruments must be thoroughly cleaned; installation of effective extraction and ventilation systems.
4. Interaction with other sectors
Sugar is produced jointly by agriculture (crop growing) and industry (processing technology), and there are close links in the ecological and technical fields. The use of modern agricultural knowledge and methods in the growing of the raw material, particularly with regard to fertilizer and pesticide application, largely determines the technological value of beet and cane (all physical, mechanical, chemical and biological properties of the raw material). High-quality raw material facilitates the tasks of extraction and juice purification and this in turn is reflected in improved technological - and hence in the final analysis economic - performance of the factory (higher sugar yields).
Excess bagasse can be used for the additional generation of electricity for the national grid (power stations sector) or for briquette production (domestic fuel supply). Bagasse is also a raw material for the manufacture of hardboard, cardboard or paper (wood and paper sector). Molasses, as well as extracts from cane and beet, are used as the raw material for fermentation processes (fermentation technology and biotechnology sector). Sugar is processed in numerous branches of the food industry. Refined sugar can be used in drug manufacture (pharmaceuticals sector).
All sugar beet and some sugar cane processing factories are equipped with lime kilns for the production of calcium oxide and carbon dioxide, and there are thus parallels with the cement/lime sector.
There are also links with the water supply, wastewater treatment and solid waste disposal sectors generally.
5. Summary assessment of environmental relevance
The impact on the environment from the sugar extraction process and the processing of the by-products from it are manifold, but can be kept to a reasonable, and in part legally prescribed, minimum level by means of established methods and processes. In new beet sugar factories the proportion of costs required for installations to protect the environment stands at some 15 to 20 % of total investment costs, while the figure for cane sugar factories is 10 to 15 %.
The wastewater produced can be minimised by optimum design of internal water circuits and the use of established purification processes (lagoon degradation/biological treatment plants). The rational control of the process must prevent any sugar solutions entering water circuits. This not only reduces pollution but increases profitability. Dumps for filter residues and earth can be used for soil conditioning once the load has been degraded. The production of fuel in the form of biogas should be taken into account when planning new factories.
Emissions from power stations and drying plants can be contained with the treatment technologies which have now been developed. A large quantity of soot and ash must be expected in the waste gas, particularly where bagasse is used as fuel, and consequently installations to optimise the combustion process and waste gas purification must be provided.
The open design of factories in warmer climates appears to obstruct possible noise prevention measures, thus noise nuisance would seem to be avoidable only by siting factories at an appropriate distance from residential areas.
In principle the environmental impact caused by sugar factories can be minimised by current technology. In the preparatory phase, it must be ensured that the plant installed will continue to be both fully operational and fully used for many years. This calls for the training of specialists at a technical level who realise the need for regular maintenance work. Training projects for sugar technicians and workmen can be appropriately integrated in sugar factories.
Sugar factories contribute to the general economic development of a country, including the intensification of agriculture, infrastructural improvement, start of the general industrialisation of rural areas and job creation in agriculture and manufacture, all of which attracts the potential workforce in the surrounding area. This generally leads to the uncontrolled growth of local communities and overburdening of the infrastructure and public services. Settlements in the immediate vicinity of the site must therefore be prevented from the outset. To minimise detrimental effects at the earliest possible stage, close cooperation must be sought at planning stage with the relevant authorities on the regional development plan. Likewise, the affected population groups - and this includes women - should be involved in the decision-making process at all planning phases so as to resolve environmental problems which may arise, e.g. land-use conflicts.
(1) Achtzehnte Allgemeine Verwaltungsvorschrift über Mindestanforderungen an das Einleiten von Abwasser in Gewässer (Zuckerherstellung), January 1982.
(2) Autorenkollektiv, Die Zuckerherstellung, Fachbuchverlag Leipzig, 1984.
(3) Bronn W.K.: Untersuchung der technologischen und wirtschaftlichen Möglichkeiten einer Abfallminderung in Hefefabriken durch Einsatz von anderen Rohstoffen anstelle von Melasse, Forschungsbericht, 1985.
(4) Davids, P. und Lange, M.: Die TA-Luft, Technischer Kommentar, Herstellung oder Raffination von Zucker, 672 - 678, Verlag des Vereins Deutscher Ingenieure, 1986.
(5) Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung, Fachgruppe Wasserchemie, 1979.
(6) Großfeueranlagen-Verordnung, Dreizehnte Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes, 1983.
(7) Hugot: Handbook of Cane Sugar Engineering, Elsevier Scientific Publishing Company, 1972.
(8) International Commission for Uniform Methods of Sugar Analysis, Report on the Proceedings of the 20th Session, 1990.
(9) Korn, K.: Harmonisierung von Umweltschutz und Kostenbelastung an Beispielen der deutschen Zuckerindustrie, Zuckerindustrie 12, 1987.
(10) Meade, G. P., Chen J. C. P.: Cane Sugar Handbook, John Wiley Sons, N.Y. 1985.
(11) National Institute of Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, 1984.
(12) Persönliche Mitteilungen des Instituts für Landwirtschaftliche Technologie und Zuckerindustrie zu Fragen über alternative Chemikalien zur Desinfektion und Reinigung von Säften in der Zuckerindustrie, 1991.
(13) Reichel, H. U.: Auswirkungen der TA-Luft und der Großfeueranlagen-Verordnung auf die Zuckerindustrie, 1985.
(14) TA-Luft: Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz, 1986.
(15) Technische Regeln für gefährliche Arbeitsstoffe, Bundesarbeitsblatt, 1985.
(16) UNEP - Industry & Environment Overview Series, Environmental Aspects of the Sugar Industry, 1982.
(17) Untersuchungen über Desinfektionsmittel für deren Einsatz in Extraktionsanlagen, Nickisch/Hartfiel/Maud, Zuckerindustrie 108, 1983.
(18) Zucker-Berufsgenossenschaft, Lärmbereiche in der Zuckerindustrie, 1978.
Appendix 1: Flow chart - raw sugar manufacture from sugar cane
Appendix 2: Flow chart - white sugar manufacture from beet
Appendix 3: Flow chart - refining raw cane sugar
Appendix 4: Water management in a beet sugar factory
Appendix 5: Wastewater control in a cane sugar factory
Flow chart - raw sugar manufacture from sugar cane
Flow chart - white sugar manufacture from sugar beet
Flow chart - refining raw sugar cane
Water management in a beet sugar factory
Wastewater control in a cane sugar factory
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