ANYASI & OBINABO : RESISTIVITY OF BIOLOGICAL WASTES AS SOIL CONDITIONERS FOR ELECT RICAL EARTHING 873 Journal of Scientific & Industrial Research Vol. 66, October 2007, pp. 873-879 Electrical properties of biological wastes used as effective soil conditioners for electrical earthing Francis I Anyasi* and Edwin C Obinabo Electrical and Electronics Department, Ambrose Alli University, PMB 14, Ekpoma Edo State, Nigeria Received 26 December 2006; revised 28 May 2007; accepted 30 May 2007 Resistivity of cow waste, chicken waste, ashes, decayed sawdust, garden soil or earth and laterite soil is determined in perspective of improving electrical conductivity of the earth. Effect of moisture on resistivity of samples is considered. Using soil Box method, study revealed that ashes have the lowest resistivity (1.04 Ω-m), followed by chicken waste (5.84 Ω-m) and cow waste (9.88 Ω-m). Present study recommends these biological wastes as cheap sources of reducing soil resistivity of earth around embedded electrodes for electrical earthing. Keywords: Biological wastes, Electrical earthing, Soil conditioner IPC Code: H04Q1/06 Introduction When charge is transferred to earth through lightning, it seeks to spread rational until it is neutralized by the ambient change of whole earth mass 1,2 . Ability of the earth to accept energy depends on resistivity of soil at that particular location where lightning discharge enters the earth. Thus, before sinking an earth electrode into earth for a new installation, it is often advantageous to make preliminary survey of the soil resistivity of the surrounding site. Such a survey may produce considerable savings in electrode and installation costs necessary to achieve the required earth resistance value 3 . There is a contact resistance between electrode and soil. Where a new rod is driven into the ground, gap between rod surface and compressed soil to its side will introduce a large contact resistance. Pouring a mixture of chemicals and soil into the area around rod will provide an immediate and significant reduction in rod’s resistance. However, its resistance would fall anyway as the surrounding soil consolidates due to rainfall etc. A more environmentally acceptable way to accelerate this effect is to add a low resistivity backfill material, such as bentonite slurry, as the rod is driven in. By continuously pouring the mixture into the hole during driving process, a sufficient quantity is dragged down to fill most of the voids around rod and lower its overall resistance 4 . Adding bentonite or marconite, in a trench or larger drilled hole around the electrode has effect of increasing surface area of earth conductor, assuming resistivity of the added material is lower than that of the surrounding soil. Effect of Soil Properties in Earthing Following soils in ascending order have higher electrical resistance as conditioners for electrical earthing 5 : i) Wet marshy lands, or lands containing ashes, cinders or brine waste; ii) Clay, loamy soil, arable land clay; iii) Clay and loamy mixed with varying proportion of gravel and sand; iv) Damp and wet sands; v) Dry sand; and vi) Gravel and stones. High electrical resistance of soils can be lowered by chemical treatment in the neighborhood of earth electrode. As addition of salts into soil moisture content improves the conductivity to a large extent, small quantity of salt reduces soil resistance (80%). In a chemical treatment of soil to increase electrical resistivity, earth electrode should be buried minimum 3 m into the ground with charcoal and coke powder mixed with chemical salts (NaCl, CaCl 2 , MgCl 2 or MgSO 4 ) placed in a circular trench around but not touching the electrode. This treatment is effective but chemicals are dissipated by natural drainage of the soil and also electrodes get corroded. *Author for correspondence E-mail: francanyasi2000@yahoo.com