792
I. C. Ribeiro et al.
A deep literature review by Valente et al. (2009) point out that composting is
affected by the interdependence and interrelationship of parameters such as moisture content, oxygen ratio, Carbon/Nitrogen ratio (C/N), the granulometry, and the
porosity of the material to be composted, with all the process affected by the adopted
management. In the case of composting, there is a need of not only establishing
optimal conditions, but also an to face the challenge of the interrelation of these
conditions, since each material to be composted has its particularities. In this way,
the mixing of several types of organic waste is the most adequate way of trying to
balance the C/N ratio and granulometry. Besides providing the necessary nutrients
for the microbial development, this will also favor the homogenization of the composting mass obtaining a better porosity which will result in a lower compaction,
due to the greater aeration capacity.
Despite the studies that aim to reuse coffee grounds focusing on composting
techniques, biodiesel production potential, and the use of this waste as a substrate
for mushroom production, Kim et al. (2017) state that there is great potential for this
residue fraction reuse in the anaerobic digestion.
Anaerobic digestion, also known as biomethanization or biodigestion, is a process of anaerobic decomposition of organic matter, which means that it occurs in
the absence of molecular oxygen (Fernandes 1997). In these conditions, anaerobic
or facultative microorganisms promote the degradation of complex organic matter,
generating simpler and soluble compounds, assimilable by microorganisms (Chernicharo 2010). This process, besides promoting the treatment of organic waste, generates by-products, such as biogas and a biofertilizer. These by-products can be used
for energy generation and as fertilizer, respectively.
Luz et al. (2017) point out that, despite the high lignin content of coffee grounds,
there is a great potential for energy reutilization, since it has a large amount of lipids
(more than 25%), which are the main substrates to methane conversion. The coffee
grounds are a residue with high percentage of volatile solids (VS) in relation to the
total solids content (83.5%) (Bizzo 2003). This demonstrates its degradability by the
anaerobic route, generating biogas because the higher is the VS content, the higher
is the gas generation rate.
According to Luz et al. (2017) the potential of energy utilization of coffee grounds
by anaerobic digestion is so favorable that, the production of biogas obtained from
this type of waste is similar to the one produced with biodigestion of bovine, porcine,
and poultry manure, a technology already consolidated and used worldwide for the
treatment and recovery of these wastes (Konzen 2005; Luz et al. 2017).
In the scope of the Environmental Policies of several countries of the world, such
as United States, Germany, Spain, Portugal, and Brazil (after 2010), the valorization
of waste is essential to promote sustainability and consequently a better quality of
the environment. Thus, the recovery of organic waste, both by composting and by
anaerobic digestion, is essential to achieve this objective (Karlsson et al. 2014).
I. C. Ribeiro et al.
A deep literature review by Valente et al. (2009) point out that composting is
affected by the interdependence and interrelationship of parameters such as moisture content, oxygen ratio, Carbon/Nitrogen ratio (C/N), the granulometry, and the
porosity of the material to be composted, with all the process affected by the adopted
management. In the case of composting, there is a need of not only establishing
optimal conditions, but also an to face the challenge of the interrelation of these
conditions, since each material to be composted has its particularities. In this way,
the mixing of several types of organic waste is the most adequate way of trying to
balance the C/N ratio and granulometry. Besides providing the necessary nutrients
for the microbial development, this will also favor the homogenization of the composting mass obtaining a better porosity which will result in a lower compaction,
due to the greater aeration capacity.
Despite the studies that aim to reuse coffee grounds focusing on composting
techniques, biodiesel production potential, and the use of this waste as a substrate
for mushroom production, Kim et al. (2017) state that there is great potential for this
residue fraction reuse in the anaerobic digestion.
Anaerobic digestion, also known as biomethanization or biodigestion, is a process of anaerobic decomposition of organic matter, which means that it occurs in
the absence of molecular oxygen (Fernandes 1997). In these conditions, anaerobic
or facultative microorganisms promote the degradation of complex organic matter,
generating simpler and soluble compounds, assimilable by microorganisms (Chernicharo 2010). This process, besides promoting the treatment of organic waste, generates by-products, such as biogas and a biofertilizer. These by-products can be used
for energy generation and as fertilizer, respectively.
Luz et al. (2017) point out that, despite the high lignin content of coffee grounds,
there is a great potential for energy reutilization, since it has a large amount of lipids
(more than 25%), which are the main substrates to methane conversion. The coffee
grounds are a residue with high percentage of volatile solids (VS) in relation to the
total solids content (83.5%) (Bizzo 2003). This demonstrates its degradability by the
anaerobic route, generating biogas because the higher is the VS content, the higher
is the gas generation rate.
According to Luz et al. (2017) the potential of energy utilization of coffee grounds
by anaerobic digestion is so favorable that, the production of biogas obtained from
this type of waste is similar to the one produced with biodigestion of bovine, porcine,
and poultry manure, a technology already consolidated and used worldwide for the
treatment and recovery of these wastes (Konzen 2005; Luz et al. 2017).
In the scope of the Environmental Policies of several countries of the world, such
as United States, Germany, Spain, Portugal, and Brazil (after 2010), the valorization
of waste is essential to promote sustainability and consequently a better quality of
the environment. Thus, the recovery of organic waste, both by composting and by
anaerobic digestion, is essential to achieve this objective (Karlsson et al. 2014).