Faecal-wood biomass co-combustion and ash composition analysis

Tosin Onabanjo Somorin,Athanasios J Kolios,Alison Parker,Ewan Mcadam,Leon Williams,Sean Tyrrel

doi:10.1016/j.fuel.2017.05.038

Abstract

Fuel blending is a widely used approach in biomass combustion, particularly for feedstocks with low calorific value and high moisture content. In on-site sanitation technologies, fuel blending is proposed as a pre-treatment requirement to reduce moisture levels and improve the physiochemical properties of raw faeces prior to drying. This study investigates the co-combustion performance of wood dust: raw human faeces blends at varying air-to-fuel ratios in a bench-scale combustor test rig. It concludes with ash composition analyses and discusses their potential application and related problems. The study shows that a 50:50 wood dust (WD): raw human faeces (FC) can reduce moisture levels in raw human faeces by ∼40% prior to drying. The minimum acceptable blend for treating moist faeces without prior drying at a combustion air flow rate of 14–18L/min is 30:70 WD: FC. For self-sustained ignition and flame propagation, the minimum combustion temperature required for conversion of the fuel to ash is ∼400°C. The most abundant elements in faecal ash are potassium and calcium, while elements such as nickel, aluminium and iron are in trace quantities. This suggests the potential use of faecal ash as a soil conditioner, but increases the tendency for fly ash formation and sintering problems.

Highlights

The development of next-generation on-site sanitation facilities is underway in many parts of the world including the United Kingdom [1,2], Switzerland [3], and Canada [4]
The moisture content (MC) values are expressed in weight percentages on an as received basis while the values for volatile matter (VM), FC and ash content (AC) are expressed as wt% on a dry-weight basis
Comparing the energy content of the dry faecal matter and wood dust, it is observed that the higher heating value (HHV) of the WD100 is 18.12 ± 2.42 MJ/kg while that of the FC100 is 23.39 ± 0.13 MJ/kg

Summary

Introduction

The development of next-generation on-site sanitation facilities is underway in many parts of the world including the United Kingdom [1,2], Switzerland [3], and Canada [4]. ⇑ Corresponding author at: School of Water, Energy and Environment, Cranfield are required to operate in areas where there may be no water, energy or sewer connections. They must be affordable: expected to cost no more than $0.05 per user per day [5]. These facilities are intended for the 40% of world’s population that have no access to sanitation and including the 1 in 7 people that rely on unhygienic toilets, unsafely emptied pit latrines or open defecation, where sanitation infrastructures are overburdened or not in existence.

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Discussion

Conclusion