Processes and balance of organic matter turnover and transformation of mineral compounds during decomposition of biogenic material in the presence of soil material
Prozesse und Bilanzen der Umsetzung von organischem Material und der Veränderung von Mineralbestandteilen von biologischem Abfallmaterial während der Erdkompostierung
by Sarra Ahmed Mohamed Saad
Date of Examination:2002-01-18
Date of issue:2006-11-08
Advisor:Prof. Dr. Brunk Meyer
Referee:Prof. Dr. Wilhelm Römer
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EnglishUnder the different possibilities of composting biogenous wastes of gardens, public greens and kitchens in the industrial Middle Europe actually prevails the biomass composting without addition of soil material- in like manner with respect to technical or to individual garden scale. There are some biochemical, ecological and hygienic problems connected with, which focus new interest on the technique of mixed composting of plant and animal wastes together with soil material, the so called ``earth composting``, which is the topic of this thesis. New aspects for research were not ``how to produce a good compost``, what ever this means, but to use the added soil material like a biological catalyst for rapid mineralization of repeatedly added organic wastes, and like a physical or a chemical sorbent of the mineralization products: Cold bio Catalytic Combustion Composting. The question was, which process does govern qualitatively and quantitatively the mineralization process of biogenic substances in contact with soil material, a problem about which only very few serious scientific literature exists. The methodical arrangement was: Dried lawn grass as a bio-standard, calcareous loess (loam), cube formed cage like reaction vessels with a compost load capacity up to 100 kg, which could be composed to a roof covered plastic mantled stack for use in field or green house without any leaching. Fractionation of the compost for chemical analysis at different stages of progress was done by sieving and suspending in water, opted for separating ``grass`` remnants (fraction F1), ``moder``, histologically not long structured but organic (F2a) and ``mull humus`` fixed chemically to the loess clay. The fractions F1 and F2a are only transition fractions for the final mineralization or mull humus formation. Percentage and relations of and between these fractions are widely independent of the amount of grass that has been added before. This and together with the fact that there occur limitations in the progress of decay after certain times strength the theory that in the case of earth composting the fix number of contact points between the microorganisms colonies and setting and fixed on the soil aggregates and the plant residue are the governing aspect. To overcome restrictions in progress of these initial stages of composting, caused by the steric fixation of bio-decay, a repeated turbo-mixing is helpful. On contrary the F2b-mull humus fraction increases, strongly dependent on the mixture ratios. This accumulation is an advantage by the use of clay containing soil admixtur e to composting, offering sites for binding humates. This humus accumulation increases the cation exchange capacity and works as a sink for N and S being liberated by mineralization. But the number of sites decreases with progressing mull formation. Since mineralization and humus formation are competitive processes, after reaching that point of exhaustion mineralization will dominate and the function of a humus sink comes to an end. For progressing accumulation of mull humus the known formula based on the repeated rate of biomass addition, specific conservation quotient and number of repetitions seems to be valid, but the observation time was not long enough to detect a saturation development in the accumulation curves. The use of the same soil material for the composting of repeated admixtures of biomaterial becomes finished much earlier than by the end of humus accumulation and that means latest at the decay of about 350 g organic residues per kg of loam. Contrary to organic carbon which leaves the system as CO2, all the other nutritive elements are kept in the system where leaching is prohibited. This involves N too, which only in some cases where compacted grass flakes promote denitrification, get lost in gaseous form. The anions of phosphate, sulphate and nitrate form salts. The total of Ca set free by mineralization is used for precipitation of phosphate and gypsum which mainly become enriched in form of precipitates. Nitrate accumulates as Na, Mg and Ca (from soil reserves) salt in the pore water solution creating there concentrations which could be toxic for plants and possibly also for soil organisms. The fate of the liberated potassium seems to be the fixation inside the expended clay minerals. The question whether a calcareous or a non-calcareous loam material is of a higher advantage for composting is with respect to the results of lower significance. The storage capacity for water and salt solution plays a more important role for the number of composting repetitions. The use of a loam material without lime and a higher degree of H+- saturation of the adsorption complex could be helpful in promoting the adsorption of K and Mg and the use of the base surplus of liberated elements for upgrading the base saturation degree of the soil material, but otherwise the expansion of three layered clay mineral, important for K fixation, will be reduced by Ca deficiency.
Keywords: cold bio catalytic combustion; earth composting; biological catalyst; mull formation; mineralization
We need a German Abstract as well!!!
Schlagwörter: We need German Keywords; cold bio catalytic combustion; earth composting; biological catalyst; mull formation; mineralization