Grounds for energetic utilization of biogas at solid domestic waste polygons located within the area of St. Petersburg

Yelistratov V.V, Maslikov V.I, Ioksha E.O, St. Petersburg State Polytechnic University, St. Petersburg, Russia

The matters of energy conservation and reducing the rate of environmental pollution make the community utilize traditional energy resources more efficiently, as well as search for other renewable and cheap energy sources, lately the solid domestic wastes refer to. As a rule, domestic wastes accumulated in large volumes, to be out of application and contaminating the environment, are considered as renewable secondary energy resources. With solid domestic wastes utilized it is possible to simultaneously resolve the urgent problems of urban land environmental pollution.

The method of solid domestic waste polygon disposal is applied all over the world. Power engineering specialists are interested in the potentialities of biogas being generated in the process of waste decomposition for a large amount of methane (up to 60%) contained in. For the period of dozen years, the rate of solid domestic waste polygon biogas emissions may total from several dozens of l/s (small polygons) to several m³/s (large polygons).

This report covers the matter of arrangement of energy generating facility comprising biogas collection system and electric energy generation heat-and-power plant to be constructed within the area of polygon PTI-1 "Volkhonsky”.

Polygon PTI-1 "Volkhonsky" is positioned in Lomonosov district, 10 km away from St. Petersburg and is valued as one of the largest polygons operated in Russian Federation. The polygon was commissioned in 1978. The area intended for waste disposal is 25 hectares. At its highest point the waste stock reaches 40 m and at medium height – 26-29 m. The amount of waste annual delivery (i.e. since 1995) makes up approximately 2 million m³, 95% of which – domestic wastes and the rest – building refuse and other kinds of wastes. Nowadays, the polygon-projected capacity is practically exhausted.

The polygon is not equipped with a biogas collection system and, as a result, atmospheric air is subject to contamination. For the purpose of assessment of biogas volumes, its emission intensity and methane content, the analysts of St. Petersburg Polytechnic University studied natural conditions of polygon PTI-1 "Volkhonsky". Besides, waste decomposition process laboratory experiments were held.

With the help of software product "DEPONIE" developed at the University, analysts could calculate the gross rate of the polygon methane emissions that within the waste decomposition conventional 60-year period made up approximately 360 million m³.  By means of the polygon 3D model the graphs of polygon surface biogas emission intensity to have been specified within the computed time interval were simulated. In terms of the polygon biogas collection system source data, the parameterized pattern of gas collecting facility to be applied at polygon “Volkhonsky” was developed.

Diesel engine power plant with 20 years period rated for production of about 290 million kW*hour was taken as a biogas utilization plant.

Considering for potential change of quota turnover that may occur in case of reduction of methane emission the rate of energetic investment was analyzed.