Digester methane production, effect

Lehtomhki A, Huttunen S, Rintala JA (2007) Laboratory investigations on co-digestion of energy crops and crop residues with cow manure for methane production effect of crop to manure ratio. Resour Conserv Recycl 51 591-609... 

Hickey, R.F., Vanderwilen, J., and Switzenbaum, M.S., The effects of organic toxicants on methane production and hydrogen gas levels during the anaerobic digestion of the waste activated sludge, Water Res., 21, 1417-1427, 1987. 

The mixed hyacinth-grass-MSW-sludge feed was pretreated with caustic soda solution at mild temperatures and pressures in an attempt to improve feed biodegradability and methane yield. Treatment temperatures (5". 25", 55°, 100", 121"C) and pressures (atmospheric and 30 psig) and dilute caustic concentrations were selected for the pretreatment studies for reasons of lower reaction vessel costs, reduced energy and chemical inputs, and to keep the salt concentration in the digester low. Alkaline treatment under these conditions is expected to be a cost-effective method for increasing methane production from cellulosic feeds (14,17). 

Nutrition has important effects on the environment as a consequence of the processes of digestion (methane and phosphorus) or a combination of digestion and metabolism (nitrogen). Methane is produced by the fermentation of foods in the gut by microbes, particularly in ruminants, and the decomposition of carbon compoimds in faeces stored as manure. Undigested phosphorus compoimds are excreted in the faeces. Undigested and waste products of the metabohsm of nitrogen compounds are excreted in the faeces and urine and the decomposition of these produces nitrous oxide (N2O). Ammonia in animal wastes is responsible for soil acidification and nutrient enrichment. 

Kaparaju P, et al. Effects of mixing on methane production during thermophilic anaerobic digestion of manure lab-scale and pilot-scale studies. Bioresour Technol 2008 99... 

Lila ZA, Mohammed N, Kanda S et al (2005) Sarsaponin effects on ruminal fermentation and microbes, methane production, digestibility and blood metabolites in steers. Asian-Aust J Anim Sci 18 1746-1751... 

Some experiments indicate positive results of including plants/plant exhacts on inhibition of methanogenesis. In one experiment Terminalia chebula, Allium sativum and the mixture of two were fed to sheep at the rate of 1% of DM1, resulted in a decreased (p=0.09) methane production by 24%, 11% and 23.5% in T. chebula, A. sativum and the mixture of the two, respectively, when expressed as L/kg digestible DM intake (Patra et al. 2010). T. chebula is a rich source of tannin (4.89% of DM), whereas, A satium is rich in essential oils. The data indicated that T. chebula was more effective as compared to garlic. The reason for low A. sativum activity might be due to the instability of alhcin, the main secondary metabolite responsible for antimicrobial activity of A. sativum. 

Fujishima, S., Miyahara, T. Noike T. 2000. Effect of moisture content on anaerobic digestion of dewatered sludge ammonia iiihibition to carbohydrate removal and methane production. Water Sci Technol. A 0>) 119-27. 

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