And again about the problem of solid domestic waste polygon biogas market utilization

Gonopolsky A.M, Professor, MGUIE

One of the main factors, the Europe countries put an end to receiving of unsorted domestic waste to be disposed at polygons since 2010, is the process of solid domestic waste biochemical fermentation that is occurred within the area of landfill polygons and resulted in generation of quite an amount of biogas emitted in atmosphere. As it is well known, the biogas composition, generally, consisting of methane (30-50%) and carbon dioxide gas (70-50%), for one thing, is fire-hazardous and, for the other thing – is the factor of “greenhouse effect” nature. The both factors should be related to hazardous anthropogenic ecological effects. Besides, any scheduled solid domestic waste polygon to be positioned within the area of Russian Federation will play quite a role in development of efficient production and consumption waste control technologies. Accordingly, the problems of solid domestic waste polygon biogas emission and minimization of its environmental impact will remain the actual ones to occur in the nearest future. The hazardous factors specified may be reduced either by cutting down of organic remain landfills by the method of intensification of waste secondary utilization process, or by extracting and utilizing of biogas at specially designed polygons, or preventing of hazardous methane emission. In light of Kioto Protocol to have been ratified by Russian Federation, the matters of SDW polygon control become urgent, due to the certain restrictions imposed by Protocol, particularly, due to the ones to specify the volumes of each country emissions (including Russian Federation).

At the same time, biogas generated as a result of biochemical fermentation of a number of organic-contained wastes (e.g. sewage sediments, agricultural product remains, food industry remains) have been utilizing as the locally produced alternative renewable fuel for many years. For the purpose of production and utilization of the above kind of fuel, the new facility and technology market is in the process of development.  

But in Russian Federation, the total solid waste polygon biogas trade market is practically subsidized. And that is, despite of great demand for any type of alternative fuel at the world markets in conditions of intensive growth of conventional hydrocarbon fuel prices.

Let us consider the objective factors preventing from development of this fuel market segment.

Upon reviewing the publications related to the problems of solid domestic waste polygon biogas utilization, it could be seen that all the documents generally cover the matter of development of polygon gas potential methods and the ones of biogas extraction technologies. It should be noted that some works are of considerable scientific-and-technological advance (authored by A.N. Nozhevnikova, A.B. Lifshitz, Ya.I. Vaisman, L.V. Rudakova, T.G. Sereda etc.). But, in this case, no researches devoted to the factors of solid domestic waste polygon biogas utilization power efficiency and ecological safeties are practically unavailable.

Let us initially consider some ecological aspects. In 2003, a number of research projects held by Vaisman Ya.I and by others proved that except of the basic components (methane, carbon dioxide, nitrogen, oxygen and hydrogen) the SDW polygon biogas contains so-called trace contaminants including toluene, ammonia, xylene, carbon monoxide, nitric oxide, formaldehyde, sulfurous anhydride, ethylbenzene, hydrogen sulfide, phenol and hydrogen cyanide.  In addition to, a number of other 2^nd class toxicity atmosphere-emission rated halogenated hydrocarbon components including dichloromethane, trichloromethane, chloroethane, trichloroethane, as well as trichloroethylene and its homologues. Along with it, the total amount of chlorine to be contained in the trace contaminants makes up 25-40 mg/m³ to be enough for exceeding of maximum permissible concentration by 250-400 times. The above data not only approves the rate of hazard of solid domestic waste polygon biogas, but also point out the need for application of special quite expensive gas-cleaning plants to be used for processing of incinerated biogas. Besides, the above data, at their high probability, prove availability of any dioxin homologues to be available in the biogas combustion products, as this kind of hazardous compounds can perfectly fit the conditions applied. Unfortunately, no similar experimental investigation was held, though a number of certain calculation data may be easily found.

Thus, market usage of solid domestic waste polygon biogas as power-plant fuel to a certain extent is limited by high cost of power generating nature preservation facilities. As per shared ratio of the basic equipment value, the cost of this kind of facilities cannot be lower than the shared value of waste incinerating factory gas cleaning plants, being achieved to 50% of a factory cost with actually the same amount of pollutants to be specified in the exhausted gas. In this case, this ratio should be just a little in excess, as the scale of production is specified at its lowers level and physical-and-chemical gas cleaning principles are of the same character.

Generally, the applied solid domestic waste polygon biogas cleaning plants are intended only for biogas preconditioning, but not afterconditioning.  As it is noted in the solid waste international association training course materials “Projecting and operation of polygons for the purpose of landfilling of solid wastes within the area of transition-economy countries”, any gas-cleaning process may be held only by the method of dehydration with use of triethylene glycol, while it is cleaned from hydrogen sulfide being passed through air-steam mixture. It should be noted that for functioning of certain recommended technological processes the rate of energy to be specified within the range of 2.0 to 3.3 kW/kg/h of cleanable biogas (compressors, pumps, fittings etc.) is required.

Let us now analyze efficiency of energy production with solid domestic waste polygon biogas used as a thermodynamic working medium. In terms of the aforesaid materials, it is stated that “There are two main methods to be used for production of energy - by means of internal combustion engines and by means of gas turbines. If the internal combustion engine is applied, the rate of gas compression should achieve to ~33 kPa. If the gas turbine is applied, the rate of compression should be higher, that is about 100 kPa”. These are absolutely true figures, but (!) when evaluating the rate of biogas energy production efficiency, all and sundry analysts, in the first place, forget to take the ones into account in the course of balance striking and, in the second place, do not consider for the fact that during its compression biogas is used to be heated up to the rate exceeding the point of its self-ignition of 82.5 ⁰Ñ and, therefore, it must be cooled down at the expense of additional energy.

 Both, the compressor and turbine operation comparative research, to have been made by the author with the help of some standard procedures, proved that being used without any energy external source the gas exhaust heat utilization system driven by the gas-turbine plant operating on incinerated solid domestic waste polygon biogas (including extraction, preparation, transportation and production energy costs) could not operate in stand-alone mode and was not repaid.

With an internal combustion engine used as an electric generator instead of the gas-turbine plant, any detailed analysis will give similar results, but nevertheless, as per the research works to have been held for analysis of biogas to be used as engine fuel in terms of application of chemically processing products, the internal combustion engine technological scheme can not be considered as profitable due to above product high cost and availability of sulfurous impurities.

From the point of view of energy efficiency and, consequently, commercialization, only locally disposed SDW polygon biogas heating technology may be applied. But, the very one also needs for comparative analysis of the heat energy to be valued and received from different sources (heat networks, local heating boilers etc.) for the purpose of various heat applications.

Consequently, since the biogas energy output sector can be hardly exactly valued even with the up-to-date facilities used, the method of solid domestic waste polygon methane-genesis suppression and subsequent selling of Kioto Protocol quotas may be considered as the only technique suitable for commercialization.

As a rule, solid domestic waste polygon methane-genesis suppression technologies make it possible to ensure landfill mass aeration at the expense of forced (Aglietto, Rainhardt) or natural ventilation (A.M Gonopolsky, V.E Murashov).