engineering materials

1. Combustion behavior and
mechanical properties of pellets
derived from blends of animal
manure and lignocellulosic biomass

2.  The livestock sector is one of the fastest growing areas of the
agricultural economy. According to the FAO (FAOSTAT, 2019),
livestock accounts for 40% of the global agricultural output value.
Recent years have witnessed expansion and intensification of large-
scale animal farms which produce significant amounts of waste,
posing major problems for the environment and public health in
rural areas (LIFE, 2015).

3.  According to the (FAOSTAT, 2019), 1,389 million tons of livestock manure were
generated in the EU in 2016, including 171,241 tons of pig manure, 1, 090,700 tons of
cow manure, and 127,317 tons of chicken manure.
 Manure management depends on many factors, such as the farm size, the type of
manure, and local conditions (Soyer and Yilmaz, 2020); however, an improper storage
and utilization of the waste may pose a problem for the local environment. Odors and
emissions of pollutants, such as ammonia, nitrous oxide, and methane, as well as water
pollution caused by the substances leaching to the soil and groundwater, may lead to a
significant pollution risk. Storing unprocessed animal manure for long periods of time
contributes to the GHG emission levels. Reports say stored cattle manure emits 16 to 84
tCO2e (carbon dioxide equivalent) while land-applications contribute another 16 to 33.5
tCO2e (Aguirre-Villegas and Larson, 2017).

4. Tujuan Jurnal
 The aim of the work was to determinate the possibility of using animal manure in
pelletization process with agro-industrial waste to obtain high quality fuels. The
assessment concerned both combustion process of selected pellets and their
mechanical properties. The thermal behavior of valorized animal manure was
studied in an air atmosphere, using the thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC). The main goal of the experiments was to
examine the influence of the addition of agricultural waste to animal manure
feedstocks on specific parameters of combustion process. In addition, pellet
strength characteristics is investigated, such as drop strength, absorbability, and
water resistance.

5. Metode
 Samples of cotton stalk (CS) and camel manure (CAM) were collected from farms
located in the Aydin region in north-western Turkey. Cotton stalk (CS) remained in
the field after the cotton harvest and then they were collected, cut and milled.
Rapeseed oil cake (ROC) came from a rapeseed extractor press, whereas cow manure
(COM) from a dairy cattle farm. Both waste came from the Opole region in Poland.
To produce the pellets, an original formation method (Yilmaz et al., 2018; Wzorek,
2008) was applied, which consists in initial mixing and then forming in a special
device. The purpose of combining animal manure with agro-industrial waste was,
among others, to reduce the initial livestock waste moisture which affects the
physical properties and determines the material consistency, thereby affecting the
forming process. The main objective was making pellets using as much animal waste
as possible in order to produce a fuel with stable physical properties.

6. Results and discussion
 Physico-chemical properties of the material
 The proximate and ultimate analysis results, as well as the calorific values of the materials are presented
in Table 1. The highest moisture content was observed for animal manure and blends made on their
basis right after mixing. The moisture content is at the level of ca. 50% for CAM80 and CAM90, and over
60% for COM90 and COM70. After several days, their moisture content decreases to approximately 20%.
Higher heating value of all samples is in the range of 17–20 MJ/kg. Cotton stalk (CS) has typically the
value of HHV similar to woody biomass, which may be in the range of 14–22 MJ/kg (Demirbas et al.,
2006). According to the literature (Çulcuoglu et al., 2001; Peterson et al., 1990), the higher heating value
of rapeseed oil cake (ROC) may be in the range of 19.5–24.5 MJ/kg. The higher heating value of animal
waste is at the same level - 17.43 MJ/kg for camel manure (CAM) and 17.10 MJ/kg for cow manure
(COM). The addition of CS and ROC to animal waste increased the calorific value of the blends. The
highest value of HHV was obtained for the blend of cow manure and rapeseed oil cake (CAM70) – 18
MJ/kg. Comparing to other studies, there is no information available about the combustion properties
of camel manure, however, the energy parameters of cow manure are similar to those obtained by
different authors (Sahu et al., 2016; Fernandez-Lopez et al., 2015).

7. Physico-chemical properties of the
material

8. Simultaneous thermal analysis
(TGA/DSC)

9. Mechanical properties of pellets
 Physical properties which determine pellet durability are important for transportation and storage
operations. Physical properties of formed fuels, such as briquettes or pellets, depend on their internal
structure to a great extent, and various additives are used in the blending, briquetting and pelletizing
techniques in order to enhance the quality of the products

10. Conclusions
 Co-pelletization of animal manure with addition of 10–30% of agroindustrial
biomass is technically possible and ensures stable physicochemical and
mechanical parameters.
 Small amount addition of agro-industrial biomass (even 10%) can considerably
change the characteristic combustion parameters such as the ignition and burn-
out temperature as well as the combustion time. The addition of ROC to COM
lowers the initiation temperature by 10 ◦C, and raises the burn-out temperature,
which in turn increases the burning time of the mixture by 1/3. In industrial
application that blends requires longer residence time and higher temperature for
complete thermal conversion. In case of camel manure (CAM) with addition of
cotton stalk (CS) the burn-out temperature and combustion time decreases. In
practice it means reduced presence of unburned residues.

11.  The heat release for camel manure blends was in the range of 9.2–9.3 kJ/kg and
from cow manure blends 10.2–10.4 kJ/kg. The addition of agro-industrial biomass
causes a change in the heat release profiles visible in the DSC curves. The heat
release curves become flat, i.e. there are no pronounced DSC peaks in the
devolatilization area (observed for animal manure) or in the combustion area of
carbonates (cotton stalk and rapeseed oil cake). The elimination of thermal effects in
these areas has practical technical advantages for the combustion of such mixtures.
Operational problems are prevented and device reliability is increased by lowering
the thermal load on the ignition chamber in the grate boilers or by reducing
temperature distribution gradients in the pulverized fuel boiler chambers.

12.  Adding 10–30% of agro-industrial waste to animal manure did not cause any
major changes of the pellet strength parameters which remain at similar levels
for all type of biofuels in the range of 80–85%.
 The water has a destructive impact on the drop strength index which
dramatically decreases once water has been absorbed by pellets.
 10–15% moisture content of pellets determines their stability and durability,
therefore it should be maintained during storage.