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ENERGY USE OF BIODEGRADABLE MUNICIPAL WASTE AT CEMENT PLANTS

Jaroslav Kucerova

Abstract

In the Czech Republic, the obligation of municipalities to ensure their residents separated collection of biodegradable municipal waste (BDW) was enacted, nevertheless the issue of further management of thus collected waste has not been satisfactorily solved so far. Material recovery of bio-waste is difficult as capacity of biogas stations and composting plants is not relevantly adequate for processing such a huge amount of material. Also the disposal of final products (compost substrate, etc.) is relatively low and their sales do not cover operating costs. Due to this and other reasons (strict legislative requirements regarding management of kitchen waste and application of composts and purified biological sludge to arable land), most bio-waste is still being deposited at landfills. Since BDW has certain energy potential, it is more than desirable to seek possibilities for its thermal processing. The physical and chemical qualities of the material imply that it contains a considerable amount of moisture which could be a limiting factor. On the other hand, results of laboratory analyses proved that it contains only a limited number of toxic substances. During clinker manufacture at cement kilns, it is necessary to reach extremely high temperatures which requires incineration of huge amounts of suitable and high-calorific fuels which, in addition, have to contain certain necessary elements (carbon, iron). Adversely, chlorine content is completely undesirable. Thus cement plants seek ways how expensive fuels could be replaced by various types of alternative fuels. Therefore at Lafarge cement company (joint-stock company) in Cizkovice in Northern Bohemia, there has been research taking place with the aim to find an optimum type of alternate fuel or additional fuel. In relation to this, there were also several test incinerations of BDW and relevant laboratory analyses of random samples were done together with creation of mathematical models. It has been proved that in the mixture with crushed waste from plastic, BDW can be considered good alternative fuel as the solid phase of bio-waste burns completely and the resulting decay products are chemically stabilised in the cement structure. However, the is still the problem of necessity of mechanical-biological processing waste before starting thermal process because such processing plants are not operated in the Czech Republic at all due to high financing costs.

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DOI resolver: doi.org/10.5593/sgem2017/42/s17.031

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