Research Paper
Operating parameters for three resource recovery options
from slow-pyrolysis of faecal sludge
M. Gold, M. Cunningham, M. Bleuler, R. Arnheiter, A. Schönborn,
C. Niwagaba and L. Strande
ABSTRACT
Slow-pyrolysis is a treatment technology that is being explored for treatment of faecal sludge (FS)
from onsite sanitation technologies. Next to pathogen inactivation, the technology produces
treatment products. Revenues from these products could offset treatment costs and contribute to
financially viable sanitation. In comparison to lignocellulosic biomass and other biowastes, little
information is available on operating parameters for FS pyrolysis to produce char for different
resource recovery options. In Kampala, Uganda, this bench-scale study investigated the influence of
two major operating parameters, hold time (10, 20 and 40 minutes) and pyrolysis temperature (350,
450 and 600
C) for pyrolysis of FS into char for solid fuel production, soil enhancement and carbon
sequestration. Hold time: 10 min was the most suitable hold time for all resource recovery options as
char characteristics had only minor variations between hold times. Temperature: Char characteristics
identified 350
C as the most suitable for fuel production and 450 or 600
C for carbon sequestration.
FS char had characteristics for soil enhancement comparable to biowaste and lignocellulosic
biomass chars, with heavy metal concentration exceeding guideline concentrations. The most
suitable temperature needs to be selected based on plant and soil type, and legal regulations.
M. Gold (corresponding author)
M. Cunningham
L. Strande
Sandec: Department of Sanitation, Water and Solid
Waste for Development,
Eawag: Swiss Federal Institute of Aquatic Science
and Technology,
8600 Duebendorf,
Switzerland
E-mail: moritz.gold@eawag.ch
M. Bleuler
R. Arnheiter
A. Schönborn
Institute of Natural Resource Sciences,
Zurich University of Applied Sciences (ZHAW),
8200 Waedenswil,
Switzerland
C. Niwagaba
Department of Civil and Environmental
Engineering, College of Engineering, Design, Art
and Technology,
Makerere University,
P.O. Box 7062, Kampala,
Uganda
Key words | char, pyrolysis, sanitation, treatment, Uganda, wastewater
NOMENCLATURE
L litre
mm millimetre
C degrees Celsius
% per cent
min minute(s)
mol mole
g gram
mL millilitre
MJ kg
1
mega joule per kilogram
cmol kg
1
centimoles per kilogram
mg kg
1
milligram per kilogram
ng kg
1
nanogram per kilogram
INTRODUCTION
Approximately 2.8 billion (10
9
) people rely on onsite tech-
nologies for access to sanitation (World Health
Organization/United Nations Children’s Fund (WHO/
UNICEF) ). In low-income countries, faecal sludge
(FS) collected in onsite sanitation technologies is inade-
quately managed, resulting in negative implications for
public and environmental health, and economic develop-
ment (Hutton & Haller ; Mara et al. ). A current
challenge in FS management is the lack of long-term operat-
ing treatment plants. If treatment plants do exist, they often
fail due to a lack of financial resources for operation and
maintenance (Bassan et al. ). Designing treatment
707 Research Paper © IWA Publishing 2018 Journal of Water, Sanitation and Hygiene for Development | 08.4 | 2018
doi: 10.2166/washdev.2018.009
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