Environmental safety, biodegradation

Linear alkylbenzenesulfonate showed no deleterious effect on agricultural crops exposed to this material (54,55). Kinetics of biodegradation have been studied in both wastewater treatment systems and natural degradation systems (48,57,58). Studies have concluded that linear alkylbenzenesulfonate does not pose a risk to the environment (50). Linear alkylbenzenesulfonate has a half-life of approximately one day in sewage sludge and natural water sources and a half-life of one to three weeks in soils. Aquatic environmental safety assessment has also shown that the material does not pose a hazard to the aquatic environment (56). 

Ingerslev F. and B. HaUing-Spiensen (2001). Biodegradability of metronidazole, olaquindox, and tylosin and formation of tylosin degradation products in aerobic soil-manure slurries. Ecotoxicology and Environmental Safety 48 311-320. 

Shimp, R. J. Young, R. L. (1988). Availability of organic chemicals for biodegradation in settled bottom sediments. Ecotoxicology and Environmental Safety, 15, 31—45. 

Chen, M., Hong, C. S., Bush, B. Rhee, G-Y. (1988). Anaerobic biodegradation of polychlorinated biphenyls by bacteria from Hudson River sediments. Ecotoxicology and Environmental Safety, 16, 95-105. 

Ward T.E. (1988) Biodegradation of linear alkylbenzene sulphonate (LAS) in sludge amended agricultural soils. To be submitted to Ecotox. and Environmental Safety. 

The main characteristics that determine the level of production of particular surfactants, aside from physico-chemical properties, are cost, availability of raw materials and environmental safety. The latter is characterized primarily by biodegradability, which is defined as the time required to reduce the surfactant concentration in the ambient medium by a given factor [26], The synthesis of surfactants with good biodegradability is an important task, as the environmental issues has become of a major concern. For example, the accumulation of surfactants within the adsorption layers formed in natural water reservoirs affects the life of various living organisms... 

To know the correlation between the structure of a polymer and its biodegradability is important, both for environmental safety reasons, and to be able to design new tailor made biodegradable plastics. 

Parsons, J.R. Covers, H.A.J. 1990. Quantitative structure-activity relationships for biodegradation, Ecotoxicology Environmental Safety, Vol. 19, No 2, pp. 212-227. 

Shi, J. et al.. Biodegradable High Solubility Alkyl Sulfate Surfactants—Environmental Safety Profiles, World Surfactants Congress, 5th, Firenze, May 29-June 2, 2000. 

An important aspect of biodegradation, which is often forgotten, is the importance of specific environmental conditions. Biodegradability can differ from one environment to another therefore, it is important to develop different standards for different environments. This includes not only composting and water but also soil, landfill, marine and biogasification. Again, discussion on the acceptance criteria is not limited to biodegradation, but also to compatibility with the system and environmental safety. 

In addition, there was a common opinion to include not only degradability criteria but to immediately include criteria related to environmental safety a biodegradable polymer cannot be accepted for degradability when at the same time it is toxic. 

The norms of compostability specifications can be considered as umbrella norms in which various necessary characteristics are summarised, along with the test methods on how to check these and the necessary pass levels to be met. An overview of the main characteristics is given in Figure 5.7. Two main characteristics are related to environmental safety, which in the case of composting falls back to compost quality chemical analyses and ecotoxicity. Two other characteristics are related to degradation biodegradation and disintegration. 

In Japan a certification system has been started by the Biodegradable Plastics Society (BPS), an industry association on biodegradable plastics, which in many aspects is different from the European and American systems. The main focus of the system is biodegradability and environmental safety. Compatibility with a typical biological waste treatment system or disintegration within a specific time period is not an issue at this stage. 

Tests for biodegradation are used to predict how quickly and completely hydrocarbons will break down in the environment. However, these tests can underestimate a chemical s ability to biodegrade if they do not examine real-world factors, such as the effects of waste water treatment or microorganism acclimation. Because biodegradability is widely recognized as an indicator of environmental safety, it is critical that realistic test conditions be used to determine biodegradability. 

Regulatory Authorities set regulations for products and monitor claims for environmental safety (risk) and biodegradation in contact environments on disposal or use such as soil, water, compost, landfill, etc. 

A major concern in this technical endeavor to develop commercially viable biodegradable polymers which still needs resolution, as will become obvious later, is the differentiation of the terms environmental safety and biodegradation. The terms are related but have been somewhat confused and misunderstood in the rush to develop the wastemanagement of polymers by developing biodegradable polymers. This misunderstanding has lead to limitations in test... 

Standards are essential to ensure the environmental safety of compost. Hydrocarbon plastics do not biodegrade rapidly in compost or in soil and it must be demonstrated that, like of nature s wastes, they do not accumulate in the soil. Standards for biodegradability and compostability of plastics must therefore address, not only the question of non-accumulation of any long-lasting plastics residues in the soil substances but also the safety of any non-degradable residues. These aspects will be discussed in the light of recent scientific studies. 

In conclusion, it is noteworthy that cyclodextrins, liposomes and chitin derivatives are all readily available from renewable biochemical sources and offer advantages of biodegradability and safety in use. However, it needs to be borne in mind that this fact alone does not necessarily mean that they are entirely environmentally innocuous in the long run. Demands on resources for the husbanding and processing of bioforms that may be necessary in order to sustain demand for commercially viable qualities and quantities can exert deleterious effects, not least because they may give by-products that present problems of utilisation or disposal [70]. 

Over the last decade the use of carriers has declined markedly and continues to do so, essentially for health, safety and environmental reasons [118-121]. In some countries these products are now virtually banned. Nearly all carrier compounds exhibit all or some of the following toxicity, physiological irritancy or poor biodegradability (Table 12.7). Typical pollution loads for comparable high-temperature and carrier methods are given in Table 12.8. 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

Apart from the pure process-driven requirements of the disintegration within a defined time span and the proof of ultimate biodegradability, it is necessary to make sure that there is no negative impact of degradation products or intermediates of the degradation process on the environment. Adequate information has to be provided for a comprehensive assessment of environmental and toxicological safety. 

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