Synthesis, characterisation and evaluation of slow nitrogen release organic soil conditioners from South African technical lignins

Tyhoda, Luvuyo (2008-03)

Dissertation (PhD) -- University of Stellenbosch, 2008.

Thesis

ENGLISH ABSTRACT: Today there is renewed interest in using technical lignins and similar ligneous materials as soil fertilising materials as they are available in large quantities from the pulping and agricultural industries. In addition, excessive application of inorganic fertilisers results in ground water pollution, especially in sandy soils through leaching of nitrogen. Lignin is an important precursor of humic material in soils and with modification, can be used as a raw material to produce slow nitrogen release fertilisers (N-lignins). This can be done using a reaction process called oxidative ammonolysis. This process has been developed over the years by the Institute of Plant and Wood Chemistry of the Technical University of Dresden in Germany, and a patent has been obtained for an ambient pressure based, oxidative ammonolysis. The patented product obtained from this process which is prepared from low-grade brown coal (due to its similarity to lignin) is trade named NOVIHUM™. It is a slow nitrogen release and long lasting organo-mineral fertiliser which has similar properties as natural humic substances. This project focussed on the characterisation and use of industrial residues such as technical lignins and similar ligneous materials which are produced by the South African pulping and agricultural industries, and on the production of N-lignins according to the patented NOVIHUM™ technology. Three technical lignins, one derived from the sulphite pulping process (a calcium lignosulphonate), the second from sugar cane bagasse (Sucrolin), and a third a, partially stripped sugar cane bagasse (a lignocellulosic residue with a low lignin content) were subjected to oxidative ammonolysis. A Kraft lignin, lndulin AT, from Westvaco, USA was used for comparison. The N-lignin products obtained were characterised and evaluated in plant growth trials.

AFRIKAANSE OPSOMMING: Daar is vandag hemude belangstelling in tegniese ligniene en soortgelyke lignienagtige materiale om hulle as grondbemestingstowwe te gebruik, hoofsaaklik omdat hulle in groot hoeveelhede in die pulp- en landbouindustrie beskikbaar is. Daarmee saam lei die oormatige aanwending van anorganiese misstowwe tot grondwaterbesoedeling, veral in sandgronde as gevolg van uitloging van stikstof. Lignien is 'n belangrike voorloper van humusagtige materiaal in grond en kan mbv chemiese modifikasie as grondstof vir stadigvrystellende stikstofmisstowwe (N-ligniene) gebruik word. Dit kan met 'n proses, genoem oksidatiewe ammonolise, uitgevoer word. Hierdie proses is die af gel ope tyd deur die Plant en Houtchemie-instituut aan die Tegniese Universiteit van Dresden in Duitsland ontwikkel en die oksidatiewe ammonolise by atmosferiese druk is gepatenteer. Die gepatenteerde produk wat mbv hierdie proses vanaf lae-graad bruinkool (agv sy soortgelyke eienskappe as lignien), vervaardig is, word in die handel NOVIHUM™ genoem. As 'n langwerkende, organominerale misstof besit dit soortgelyke eienskappe as natuurlike humusagtige stowwe. Hierdie ondersoek fokus op die karakterisering en gebruik van industriele residue soos tegniese ligniene en soortgelyke lignienagtige materiale wat deur die Suid Afrikaanse pulp- en landbouindustrie produseer word, en om N-ligniene volgens die gepatenteerde NOVIHUM™ tegnologie daarvan te vervaardig. Drie tegniese ligniene, een afkomstig van die sulfietverpulpingsproses ('n kalsiumlignosulfonaat), die tweede van suikerrietbagasse (Sucrolin) en 'n derde, 'n gedeeltelik verwyderde suikerrietbagasse dws 'n lignosellulose-agtige residu met 'n lae lignieninhoud, is aan oksidatiewe ammonolise onderwerp. Indulin AT, 'n Kraftlignien, afkomstig van die firma Westvaco, VSA, is as verwysing gebruik. Die N-lignienprodukte wat verkry is, is gekarakteriseer en dmv plantgroeitoetse evalueer.

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