methanol my biodegrade but into what? if it degrades into methane that is a green house gas?
----Original Message Follows---- From: Keith Addison <[EMAIL PROTECTED]> Reply-To: Biofuel@sustainablelists.org To: biofuel@sustainablelists.org Subject: [Biofuel] Methanol and wastewater treatment systems Date: Mon, 10 Oct 2005 02:10:47 +0900 9.1.1 Microorganisms The toxicity of methanol to each of three bacterial groups, i.e., aerobic heterotrophic, Nitrosomonas and methanogens (key agents in the natural recycling of organic material in the environment and in wastewater treatment systems), was described by Blum & Speece (1991). The following IC50 values (mg/litre) (the concentration that inhibited the culture by 50%) compared to the uninhibited controls were reported: Nitrosomonas (after 24-h exposure), 880 mg/litre; methanogens (after 48-h exposure), 22 000 mg/litre; and aerobic heterotrophs (after 15-h exposure), 20 000 mg/litre. Methanol was found to be completely inhibitory to ammonia oxidation by Nitrosomonas bacteria at a concentration of 5 x 10-3 M (about 160 mg/litre) (Hooper & Terry, 1973)... ... An experimental EC50 value (the concentration that reduced the maximum observed biodegradation rate by 50%) for methanol of 2.8 mol/litre (89.7 g/litre) was obtained in a system employing an enriched mixed microbial culture derived from domestic waste water in the USA (Vaishnav & Lopas, 1985). 9.2.1 Plants Hemming et al. (1995) determined the effect of methanol on the respiration of pepper (Capsicum annuum), tomato (Lycopersicon esulentum) and petunia (Petunia hybrida). Whole plants were exposed to either methanol vapour or methanol solution. The general response to methanol was the same for the three species, with a respiratory rate increase of up to 50% at the lower methanol concentrations tested. The response was the same for exposure to methanol vapour or solution. Exposure of a single leaf resulted in a systemic response throughout the whole plant within a few hours. The response lasted for several weeks. Decreased metabolic rates and waterlogged appearance were reported in plants following a brief exposure of a leaf to methanol concentrations > 30%. Root tissue was reported to be more sensitive; a decrease in metabolic rate was reported following brief exposures to > 10% methanol. 10.2 Evaluation of effects on the environment Methanol is readily degraded in the environment by photo- oxidation. Half-lives of 7-18 days have been reported for the atmospheric reaction of methanol with hydroxyl radicals. Methanol is readily biodegradable under both aerobic and anaerobic conditions in a wide variety of environmental media. Many genera and strains of microorganisms are capable of using methanol as a growth substrate. Generally 80% of methanol in sewage systems is biodegraded within 5 days. Methanol is a normal growth substrate for many soil micro- organisms, which are capable of completely degrading methanol to carbon dioxide and water. Methanol is of low toxicity to aquatic and terrestrial organisms and it is not bioaccumulated. Effects due to environmental exposure to methanol are unlikely to be observed, unless it is released to the environment in large quantities, such as a spill. In summary, unless released in high concentrations, methanol would not be expected to persist or bioaccumulate in the environment. Low levels of release would not be expected to result in adverse environmental effects. -- From: United Nations Environment Programme / International Labour Organisation / World Health Organization: International Programme On Chemical Safety, Environmental Health Criteria 196 - Methanol, from IPCS INCHEM, "Chemical Safety Information from Intergovernmental Organizations", in cooperation with the Canadian Centre for Occupational Health and Safety (CCOHS) http://www.inchem.org/documents/ehc/ehc/ehc196.htm FWIW I think 22 000 mg/litre is 2.8 per cent. Best wishes Keith _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/ _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
