Effective energy exploitation from horse manure combustion

Abstract

We investigated the exploitation of horse manure for energy recovery by combustion. First, the impact of the waste origin and management (storage conditions) was evaluated in terms of elemental analysis, moisture content, heating value, and ash melting temperature. Besides some carbon loss over the time, horse manure origin and management policy do not impact its profitable exploitation by combustion. More relevant, the ignition tests disproved the current industrial opinion that combustion of manure alone is difficult, without the addition of auxiliary fuel, like wood shavings. It has been demonstrated through ignition tests that the major limitation in manure combustion is just the high moisture content (approx. 60% w.b.). The study focused on overcoming the detrimental effect of the large moisture content, and specifically its removal efficiency. The latter requires the understanding of manure permeability which is determined by the bedding material and the stable management. Here we provide indications of the impact of the manure composition and its sample size on the efficiency of moisture removal, whose energy impact must be minimized for an effective energy recovery. The energy balance confirms that the total removal of 62% w.b. moisture reduces by 23% the potential energy content of the manure; this drying penalty on energy is largely offset by the dramatic improvement in reactivity of the residual solid fuel.

Keywords: Bedding material; Biowaste; Drying; Faeces; Manure; Renewable energy.