energies

Review
Potential Use of Industrial Biomass Waste as a Sustainable
Energy Source in the Future
Tomasz Kalak

Department of Industrial Products and Packaging Quality, Institute of Quality Science,

Poznań University of Economics and Business, Niepodległości 10, 61-875 Poznań, Poland;
tomasz.kalak@ue.poznan.pl

Abstract: Aspects related to the growing pollution of the natural environment and depletion of
conventional fossil fuels have become the motive for searching for ecofriendly, renewable, and
sustainable alternative energy sources. Particular attention is paid to industrial waste, especially
waste of biomass materials, which can be converted into biofuels and energy that meets the growing
needs of humanity. The use of biomass for energy purposes is less damaging to the environment, the
materials are low-cost, locally available in large quantities, and create employment opportunities for
workers in suburban and rural areas around the world. This article discusses issues related to the use
of waste biomass materials as renewable energy sources. The current energy situation in the world is
analyzed in terms of production, consumption, and investments in green energy. Types of biomass
and individual physicochemical and energy properties of waste plant materials obtained for energy
purposes are described. Currently available methods of converting biomass into energy, including
mechanical, thermal, and biochemical techniques are discussed. The conducted analysis indicates the
possibility of using it as a competitive source of electricity and heat. Understanding the properties
of biomass materials allows us to understand the right way to use them for energy and reduce the
consumption of fossil fuels in the future.

Keywords: growing demand for energy; renewable energy sources; biomass waste materials; energy
usefulness of biomass; alternative biofuels; sustainable energy economy

Citation: Kalak, T. Potential Use of

Industrial Biomass Waste as a
1. Introduction
Sustainable Energy Source in the
Future. Energies 2023, 16, 1783. Fossil fuel resources are not renewable, but their amounts are limited and close
https://doi.org/10.3390/en16041783 to exhaustion due to overexploitation. According to analyses, global oil resources are
extracted at a rate of approx. four billion tons per year. If currently known oil reserves
Academic Editors: Adrian Ilinca
continue to be exploited at or above current levels, it is predicted that all reserves could be
and Alberto-Jesus Perea-Moreno
exhausted within the next 40 years. The deadline may be slightly extended if new reserves
Received: 8 December 2022 are found [1]. The continuous exploitation of fossil fuels generates side effects for the
Revised: 26 January 2023 environment. As a result of their combustion, approximately 21.3 billion tons of CO2 , along
Accepted: 8 February 2023 with other harmful gases, are released into the atmosphere globally, causing the greenhouse
Published: 10 February 2023 effect. It is estimated that natural processes can neutralize about half of this amount of
gases. However, CO2 emissions into the atmosphere, amounting to about 10.65 billion
tons per year, are still a serious burden. Therefore, in order to ensure security, free life,
and access to energy for future generations, it is necessary to search for new, alternative
Copyright: © 2023 by the author.
energy resources that will be environmentally friendly and meet the criteria of a sustainable
Licensee MDPI, Basel, Switzerland.
economy and a zero-emission economy [2].
This article is an open access article
An opportunity for the energy sector is undoubtedly renewable energy, called bioen-
distributed under the terms and
ergy, which is stored in an organic form in a chemical state. The sustainable energy strategy
conditions of the Creative Commons
Attribution (CC BY) license (https://
in the European Union was launched by the European Commission in 1998 to implement
creativecommons.org/licenses/by/
Articles 2 and 6 of the European Treaty on sustainable development. This policy meant
4.0/).
improving the well-being of society in the long term by striving to maintain a balance

Energies 2023, 16, 1783. https://doi.org/10.3390/en16041783 https://www.mdpi.com/journal/energies

Energies 2023, 16, 1783 2 of 25

between energy security, meeting social needs, the competitiveness of the economy, and
environmental protection. A sustainable energy system should ensure energy security,
be competitive, effective, and support the dynamics of economic growth, and take into
account human health and protect the environment [3,4]. Therefore, taking into account
the aspirations in energy and environmental policy, renewable energy sources include
biomass as the totality of organic animal or vegetable matter, including, in particular, the
biodegradable fraction of products, wastes, and residues from agriculture, forestry, industry,
households, as well as other substances obtained as a result of processing such biomass
materials [5]. Agricultural biomass material has the advantage of absorbing the increasing
levels of CO2 in the atmosphere through biological CO2 sequestration. Biomass waste as a
renewable energy source can be converted into bioenergy using various technologies [6].
The European Union’s strategy on biofuels states that new technologies for obtaining
and using renewable fuels need to be developed, especially through the management of
agricultural by-products and other waste, including biodegradable industrial waste [7].
Biomass material belongs to renewable energy resources due to the fact that CO2
emitted in the processes of its combustion or thermal conversion does not increase the CO2
content in the atmosphere. Biomass is an organic material obtained from plants growing
through, among others, the process of photosynthesis. Plants assimilate CO2 released into
the environment as a result of the degradation processes of other plants as part of a closed
cycle. Absorption of solar radiation by vegetation, CO2 assimilation, and transformation
into organic material is of great importance on many levels. Thanks to this, the life of
terrestrial and aquatic organisms that use this energy is possible. Therefore, the use of
biomass for energy purposes only leads to CO2 emissions into the atmosphere, which
will then be used by plants to reproduce biomass [8–10]. Plants in the form of biomass
are decomposed by microorganisms or can be burned and turned into ashes in thermal
incinerators and co-incineration in kilns, converting chemical energy into mechanical or
electrical energy. If biomass undergoes natural biocomposting processes, it gives back
carbon in the form of methane or CO2 to the atmosphere. The general closed cycle of
biomass energy circulation is shown in Figure 1 [11]. It is estimated that most developed
countries will use biomass waste to meet more than 50% of their net energy needs by
2050. Agricultural biomass is rich in cellulosic raw materials, which are important in the
production of biofuels, thereby reducing waste and meeting energy needs with no risk of
losing valuable food [12].
From an energy point of view, biomass is composed of waste of plant and animal
resources and at the same time, their energy potential. Using it for energy purposes
will reduce dependence on traditional fossil fuels due to the abundance of resources,
local availability, and lower costs. In many underdeveloped countries, large amounts of
firewood are used for cooking and other household heating purposes, as well as other parts
of agricultural and animal waste. Such large-scale unsustainable use of biomass resources
may result in exposure to air pollution. Agricultural and food waste is locally also used to
feed farm animals such as pigs, cows, bulls, chickens, ducks, and others [13].
Biomass waste is generated in huge amounts around the world, with rice straw (approx.
731.3 million tons), wheat straw (354.34 million tons), sugarcane bagasse (180.73 million
tons), and corn stover (128.02 million tons) being the most produced annually [2]. The
largest production of wheat and rice straw takes place in Asia, while the largest producer
of corn straw and sugarcane bagasse is the United States [14]. According to statistics,
approximately 950 million tons of biomass are produced annually in Europe, from which
approximately 300 million tons of fuel equivalent to petroleum fuel can be produced. These
data mean that biomass waste can provide around 65% of Europe’s total oil consump-
tion [15].
Energies 2023, 16, x FOR PEER REVIEW 3 of
Energies 2023, 16, 1783 3 of 25

.
Figure 1. The general cycle of biomass energy.
Figure 1. The general cycle of biomass energy.
The purpose of this study is to present an overview of the research conducted so far on
Biomass of
the possibility waste
usingisbiomass
generated
wasteinashuge amounts
a renewable around
energy theto
source, world,
assess with rice straw (a
the current
prox. 731.3 million tons), wheat straw (354.34 million tons), sugarcane bagasse (180.
state of knowledge, and to indicate potential future research directions. Before undertaking
million
researchtons),
on theand corn stover
discussed problem,(128.02
a numbermillion tons) being
of questions the most
regarding produced
various annually [2
aspects were
asked. What is the current availability of biomass? What is the current energy situation in
The largest production of wheat and rice straw takes place in Asia, while the largest pr
the world, including consumption and demand? What are the types and sources of biomass
ducer of cornraw
as a potential straw and sugarcane
material? What methods bagasse is theconversion
of biomass United States [14]. According
are available? What are to stati
tics, approximately 950 million tons of biomass are produced annually
the methods of energy characterization of biomass materials? Are there any barriers intoEurope,
the fro
which approximately
use of biomass materials?300Whatmillion tons scope
is the future of fuel equivalent
of biomass waste toenergy
petroleum
sources?fuel can be pr
There
duced. These
will be an data
attempt to mean that biomass
find answers waste
to all these can provide
questions and doubtsaround 65%
with the of Europe’s
support of the total o
consumption [15].
current literature, statistical data available through various databases, research results of
investigators, and reports on available and new technologies. This study may help us to
The purpose of this study is to present an overview of the research conducted so f
understand the current situation, the need to change the approach to the energy sector, and
on the possibility of using biomass waste as a renewable energy source, to assess the cu
indicate future solutions in global terms. The above considerations were an inspiration to
rent statethe
consider ofenergetic
knowledge, and to
usefulness indicate
of waste potential
biomass future
materials research
in this article. directions. Before u
dertaking research on the discussed problem, a number of questions regarding variou
aspects were
2. Biomass asked. What
Availability and is the
the current
Current availability
Global Energy of biomass? What is the current energ
Situation
situation in the world, including consumption and demand?
Huge amounts of biomass are available in various natural What
terrestrial and are the
aquatic areas,types an
sources of biomass as a potential raw material? What methods of biomass conversion a
but also as waste from human industrial activities. In accordance with World Bioenergy
Association, the total global aquatic and terrestrial biomass resources are approximately
available? What are the methods of energy characterization of biomass materials? A
4 billion tons and 1.8 trillion tons, respectively. It is estimated that the total biomass in
there any barriers to the use of biomass materials? What is the future scope of bioma
the world has the potential to contribute to the production of around 33,000 EJ (exajoules),
waste
which isenergy sources?
more than There
80 times morewill be an
energy thanattempt to find
the world’s answers
annual energy to all these questions
consumption [16]. an
doubts with(coal,
Fossil fuels the support of the current
oil, and natural gas) areliterature, statistical
still the dominant dataenergy
global available through
source and variou
databases,
account for research results
approximately 81%of of
investigators,
the total primaryandenergy
reportssupply.
on available
Renewable andenergy
new technol
gies. This study
technologies, suchmay help
as solar, us to
wind, understand
water, biomass, the currentetc.
geothermal, situation, the of
had a share need to in
14.1% change th
approach to the energy sector, and indicate future solutions in global terms. The abov
the primary energy supply in 2019. Domestic biomass supply was 56.9 EJ, of which 85%
considerations were an inspiration to consider the energetic usefulness of waste bioma
materials in this article.
Energies 2023, 16, 1783 4 of 25

was solid biomass, including wood pellets, wood chips, and other biomass sources. Liquid
biofuels accounted for 8%, municipal and industrial waste 5%, and biogas 2% [16].
Agriculture is a key area for increasing bioenergy potential in the future. There is a
great opportunity for the growth of various crops in the world, which will allow increasing
the production of not only food but also fuel using bioenergy. Another sector after forestry
and agriculture is the production of energy from municipal and industrial waste, where
the energy supply was 2.59 EJ in 2019 [16].
In 2019, 655 TWh of electricity was produced worldwide from biomass. Sources of
solid biomass accounted for 68%, and municipal and industrial waste17%. Asia produced
39% of bioenergy (255 TWh), followed by Europe with 35% (229 TWh). It was estimated
that, in total, the power plants produced around 428 TWh of bioenergy. In turn, 1.17 EJ of
heat was produced from biomass raw materials, including 53% from solid biomass sources
and 25% from solid municipal waste. Around the world, 1.35 EJ of heat was produced in
CHP plants and 0.43 EJ in Europe, which is the world leader in the production of heat from
biomass in power plants with a global share of 88% [16].
In such European countries as Poland, Denmark, and Sweden, 50% of energy demand
is covered by renewable energy. In Poland, there is a growing trend for the increasing use
of biomass materials for the production of biofuels for transport and electricity generation
due to well-developed agriculture and food production in the country. In Poland, there are
plans for at least 80% of total energy to come from renewable sources, including biomass,
and as much as 75% of biomass energy is planned to be produced from agricultural
biomass [17]. Austria, Sweden, and Finland use 13%, 17%, and 18% of biomass energy,
respectively. Austria and Sweden are trying to use more firewood to produce heat, and
there is a growing trend towards plantations of energy trees such as poplar or willow.
Some countries have favorable policies in this regard; for example, France has introduced
tax exemptions for the production of ethanol and biodiesel in order to encourage the
development of biomass technologies. Great Britain has put emphasis on the development
of effective biogas recovery systems from landfills for the production of electricity and heat.
In comparison with representatives of other continents, the United States uses biomass
for about 3% of its total energy demand, which corresponds to about 3.2 million TJ per
year [18].
According to recent literature reports, global energy production is estimated at around
27,000 TWh/year and around 2664 TWh/year in the European Union (EU) [19,20]. Waste
heat recovery of the industrial sector in the EU has been estimated at around 300 TWh/year,
of which 30% of waste heat is low-temperature heat (<200 ◦ C), 25% medium-temperature
heat (200–500 ◦ C), and 45% high-temperature heat (>500 ◦ C) [21–24]. In 2020, global
primary energy consumption decreased by 4% (564 EJ) compared to 2019 (Figure 2). This
was due to the COVID-19 pandemic and its impact on fuel consumption for transport and
other sectors of the economy. In 2021, a revival in energy consumption and its increase of
5.5% (595 EJ) compared to the previous year has been observed. However, global energy
demand continues to grow and is unlikely to decline in this sector [25].
Global energy consumption continues to be concentrated around primary energy
fuels such as coal and oil. The first place in terms of the largest consumption of primary
energy in the world is occupied by China, consuming around 158 EJ in 2021 (Figure 3).
The United States is in second place with an average consumption of around 93 EJ. It is
followed by India, Russia, Japan, Canada, Germany, and other countries [26]. Renewable
energy consumption is projected to increase annually and could reach around 247 EJ by
2050 (Figure 4) [27].
 700
700

consumption
600

energyconsumption
600
500
500

[exajoules]
[exajoules]
400
400
Energies2023,
Energies 2023,16,
16,1783
x FOR PEER REVIEW 5 5ofof26
25
300

Globalenergy
300
200
200

Global
100
700
100

00

Global energy consumption

600

500

[exajoules]
400 Energyconsumption
Energy consumptionyear
year

Figure 2.
300 primary energy
Global primary energyconsumption
consumption(2000–2021)
(2000–2021)[25].
[25].

200
Global energy
energy consumption
consumption continues
continues toto be
beconcentrated
concentratedaround
aroundprimary
primaryenergy
energy
fuels such coal and
100 as coal and oil.
oil. The
The first
first place
placeininterms
termsofofthe
thelargest
largestconsumption
consumptionofofprimary
primary
energy in0 the world
world isis occupied
occupied by by China,
China,consuming
consumingaroundaround158158EJEJinin2021
2021(Figure
(Figure3).3).
The United States
States is
is in
in second
second place
place with
withananaverage
averageconsumption
consumptionofofaround
around9393EJ. EJ.ItItisis
followed by India,
India, Russia,
Russia, Japan,
Japan,Canada,
Canada,Germany,
Germany,and andother
othercountries
countries[26].
[26].Renewable
Renewable
energy consumption
consumption is is projected to
toincrease
projectedEnergy annually
consumption
increase year and
annually andcould
couldreach
reacharound
around247247EJEJbyby
2050 (Figure
Figure 4) [27].
Global[27].
Figure2.2. Global primary energy
primary energy consumption
consumption (2000–2021)
(2000–2021) [25].
[25].

180
Global energy consumption continues to be concentrated around primary energy
consumption

160
energyconsumption

160 as coal and oil. The first place in terms of the largest consumption of primary
fuels such
140
140
energy in the world is occupied by China, consuming around 158 EJ in 2021 (Figure 3).
120
120
The United States is in second place with an average consumption of around 93 EJ. It is
[exajoules]
[exajoules]

100
100
followed
80 by India, Russia, Japan, Canada, Germany, and other countries [26]. Renewable
80
Globalenergy

energy60consumption is projected to increase annually and could reach around 247 EJ by

60
2050 (Figure
40
40 4) [27].
Global

20
20
00
180
Global energy consumption

160
140
120
[exajoules]

100 Country
Country
80
Figure
Figure3. Global
Globalprimary
primaryenergy
energyconsumption in in
2021 bybycountry [26].
Figure 3.3.Global
60 primary energy consumption
consumption in 2021
2021by country
country [26].
[26].
40
Hydroelectricity Nuclear energy Renewable energy Natural gas Oil Coal
800 20 Hydroelectricity Nuclear energy Renewable energy Natural gas Oil Coal
800 0
[EJ]
consumption[EJ]

700
700
consumption

600
600
500
500
400 Country
400
energy

3003. Global primary energy consumption in 2021 by country [26].

Figure
energy

300
200
200
Global

100 Hydroelectricity Nuclear energy Renewable energy Natural gas Oil Coal
Global

800
100
Global energy consumption [EJ]

0
700
0 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050
600 2000 2005 2010 2015 2020 2025
Energy consumption year
2030 2035 2040 2045 2050
Energy consumption year
500
Figure
Figure4.
4.Global
Globalenergy
energyconsumption
consumption(2000–2019)
(2000–2019)and a forecast
and until
a forecast 2050
until [27].
2050 [27].
Figure 4.
400Global energy consumption (2000–2019) and a forecast until 2050 [27].
According
300 to statistical data, in 2020, global bioenergy production was approximately
584 terawatt hours (Figure 5). The trend is still upward due to the changing energy sector
200
toward the use of renewable energy sources from organic, biological, and waste materials.
100
Bioenergy can come from combustion processes of biomass in the form of natural or waste
0
wood, sawdust, straw and other agricultural waste, animal excrement, sewage sludge,
2000 2005
seaweed, sugar cane, and2010 2015
other plants, 2020
organic2025
waste2030 2035
(e.g., beet 2040
pulp, corn2045
stalks,2050
grass,
etc.), vegetable oils, or animal fats. Energy consumption
The share yearenergy from renewable sources is
of global
growing
Figure 4. every
Globalyear.
energy Inconsumption
2018, 2.36 terawatts of and
(2000–2019) cumulative
a forecastrenewable energy capacity were
until 2050 [27].
recorded. Despite a steady increase in the consumption of renewable energy, unfortunately,
 mately
mately 584 584 terawatt
terawatt hours
hours (Figure
(Figure 5).
5). The
The trend
trend is is still
still upward
upward due due to
to the
the changing
changing energy
energy
sector
sector toward
sector toward
toward the the use
the use
use ofof renewable
of renewable
renewable energyenergy sources
energy sources
sources from from organic,
from organic, biological,
organic, biological,
biological, and and waste
and waste
waste
materials.
materials. Bioenergy
materials. Bioenergy
Bioenergy can can come
can come from
come from combustion
from combustion processes
combustion processes
processes of of biomass
of biomass
biomass inin the
in the form
the form
form ofof nat-
of nat-
nat-
ural
ural or
or waste
waste wood,
wood, sawdust,
sawdust, straw
straw and
and other
other agricultural
agricultural waste,
waste,
ural or waste wood, sawdust, straw and other agricultural waste, animal excrement, sew- animal
animal excrement,
excrement, sew-
sew-
age
age sludge,
age sludge, seaweed,
sludge, seaweed,
seaweed, sugar sugar cane,
sugar cane, and
cane, and other
and other plants,
other plants, organic
plants, organic
organic wastewaste (e.g.,
waste (e.g., beet
(e.g., beet pulp,
beet pulp, corn
pulp, corn
corn
Energies 2023, 16, 1783 stalks,
stalks, grass,
grass, etc.),
etc.), vegetable
vegetable oils,
oils, or
or animal
animal fats.
fats. The
The share
share of
of global
global
stalks, grass, etc.), vegetable oils, or animal fats. The share of global energy from renewa- energy
energy from
from renewa-
renewa-6 of 25
ble
ble sources
ble sources
sources is is growing
is growing
growing everyevery year.
every year. In
year. In 2018,
In 2018, 2.36
2018, 2.36 terawatts
2.36 terawatts
terawatts of of cumulative
of cumulative renewable
cumulative renewable energy
renewable energy
energy
capacity
capacity
capacity werewere recorded.
were recorded. Despite
Despite aaa steady
recorded. Despite steady increase
steady increase
increase in in the
in the consumption
the consumption
consumption of of renewable
of renewable
renewable en- en-
en-
ergy,
ergy,
ergy, unfortunately,
unfortunately,
unfortunately, it
it
it is
is
is still
still
still a
a
a small
small
small amount
amount
amount compared
compared
compared to
to
to the
the
the consumption
consumption
consumption of
of
of fossil
fossil
fossil fuels
fuels
fuels
it is still a small amount compared to the consumption of fossil fuels [28]. The global supply
[28].
[28]. The
The global
The global supply
supply
supply of of biomass
biomass for
for primary
for primary energy
energy is
is steadily
is steadily increasing
increasing from 41.6 EJ
[28].
of biomass global
for primary ofenergy
biomass primary
is steadily energyfrom
increasing steadily in 2000 tofrom
increasing
41.6 EJ 57 EJ41.6
from 41.6 EJ
EJ
in 2019
in
in
in 2000
2000 to
to 57
57
2000 to6)57 EJ
EJ in
in
EJ in 2019
2019 (Figure
(Figure
2019 (Figure 6)
6) [29].
[29]. Similarly,
Similarly, there
there is
is an
an increase
increase in
in the
the global
global produc-
produc-
(Figure [29]. Similarly, there6)is[29]. Similarly,inthere
an increase is an increase
the global in the
production ofglobal produc-
electricity from
tion
tion
tion of
of
biomass, electricity
of electricity
electricity from
from
and in 2019, biomass,
from biomass,
biomass,
it amounted and
and
andto in
in 2019,
2019,
in655
2019,
TWhit
it amounted
it amounted
(Figure 7)to
amounted to
to 655
655 TWh
655 TWh
[30]. (Figure
TWh (Figure
(Figure 7) 7) [30].
7) [30].
[30].

700
700
700
600
bioenergy
600
bioenergy
600
ofbioenergy

500
500
500
hours]
hours]
[terawatthours]

400
400
400
productionof
production
Globalproduction of

300
[terawatt

300
[terawatt

300
200
200
200
100
100
100
Global
Global

00
0
2009
2009
2009 2010
2010
2010 2011
2011
2011 2012
2012
2012 2013
2013
2013 2014
2014
2014 2015
2015
2015 2016
2016
2016 2017
2017
2017 2018
2018
2018 2019
2019
2019 2020
2020
2020
Production
Production year
Production year
year
Figure
Figure
Figure 5.
Figure5. Global
5.5.Global production
Globalproduction
Global of
productionof
production bioenergy
ofofbioenergy (2009–2020)
bioenergy(2009–2020)
bioenergy [28].
(2009–2020)[28].
(2009–2020) [28].
[28].

60
60
60
50
[EJ]
primary

50
[EJ]
primary

50
consumption[EJ]
biomassprimary
consumption

40
energyconsumption

40
40
biomass

30
Globalbiomass

30
30
20
20
20
Global
energy
Global
energy

10
10
10
00
0
2000
2000
2000 2005
2005
2005 2010
2010
2010 2015
2015
2015 2016
2016
2016 2017
2017
2017 2018
2018
2018 2019
2019
2019
Energy
Energy consumption
Energy consumption year
consumption year
year
Figure
Figure
Figure 6.
Figure6. Global
6.6.Global
Global biomass
Globalbiomass primary
biomassprimary
biomass energy
primaryenergy
primary consumption
energyconsumption
energy (2000–2019)
consumption(2000–2019)
consumption [29].
(2000–2019)[29].
(2000–2019) [29].
[29].

700
700
700
production
production
electricityproduction

600
600
[terawatt

600
[terawatt
biomass[terawatt

500
500
500
400
400
400
hours]
hours]
hours]
electricity
Globalelectricity
biomass
frombiomass

300
300
300
200
200
200
100
from

100
from
Global

100
Global

00
0
2000
2000
2000 2005
2005
2005 2010
2010
2010 2015
2015
2015 2016
2016
2016 2017
2017
2017 2018
2018
2018 2019
2019
2019
Electricity
Electricity production
Electricity production year
production year
year
Figure
Figure7.7.Global
Figure 7. Global
Figure 7.
Globalelectricity
electricityproduction
Global electricity
productionfrom
electricity production
frombiomass
production from
biomass(2000–2019)
from biomass
(2000–2019)[30].
biomass (2000–2019)
[30].
(2000–2019) [30].
[30].
In recent years, incineration of municipal solid sewage sludge using circulating flu-
idized bed combustion (CFBC) technology at temperatures up to 1000 ◦ C has become
increasingly popular in the European Union, China, and Japan. Modern incineration
plants do not emit large amounts of pollutants into the environment and atmosphere
compared to old ones due to increasingly strict legislation. As a result, it is possible to
recover thermal energy and reduce methane emissions released from landfills. It should
also be emphasized that innovative gas purification technologies are being developed
both during and after the combustion process in order to reduce pollutants harmful to
the environment [31,32]. In 2019, the global value of the waste-to-energy market was
 idized bed combustion
combustion (CFBC) (CFBC) technology
technologyatattemperatures
temperaturesup uptoto10001000°C°Chashasbecome
becomein-in-
creasingly popular
popular in in the
the European
EuropeanUnion,Union,China,China,and andJapan.
Japan.Modern
Modernincineration
incinerationplants
plants
do not emit large
large amounts
amounts of of pollutants
pollutantsintointothe theenvironment
environmentand andatmosphere
atmospherecompared
compared
to old ones due to to increasingly
increasingly strict
strictlegislation.
legislation.As Asaaresult,
result,ititisispossible
possibletotorecover
recoverther-ther-
mal energy and and reduce
reduce methane
methane emissions
emissionsreleased
releasedfrom
fromlandfills.
landfills.ItItshould
shouldalso alsobebeem- em-
Energies 2023, 16, 1783 7 of 25
phasized that innovative
innovative gas gas purification
purificationtechnologies
technologiesare arebeing
beingdeveloped
developedboth bothduring
during
and after the combustion
combustionprocess processin inorder
orderto toreduce
reducepollutants
pollutantsharmful
harmfultotothe theenvironment
environment
[31,32]. In 2019, the the global
global value
valueof ofthe
thewaste-to-energy
waste-to-energymarket marketwas wasUSDUSD35.135.1billion
billion(Fig-
(Fig-
ure 8).
USD According
According
35.1 to
to estimates,
billion (Figure estimates, this
thismarket
8). According market could
couldhave
to estimates, have reached
thisreached
market USD
USD 50.1
could50.1 billion
havebillion byby2027,
reached 2027,
USD
50.1 billionconstant
assuming by 2027,growth
constant growth
assuming of
of 4.6%
4.6% [33].
[33]. Global
constant Globalproduction
growth production
of 4.6% [33].ofofheat
heatand
Global and electricity
electricityfrom
production offrom
heat
waste
and amounted
amounted
electricity to
fromto 2.59
2.59 EJ
wasteEJ in
in2019
2019(Figure
amounted (Figure 9)
to 2.599)[34].
EJ inWorld
[34]. World total
totalenergy
2019 (Figure energy supply
supply
9) [34]. World from
from renew-
totalrenew-
energy
able energy
supply fromsources
sources
renewable and waste
wastecontinues
andenergy continues
sources to
and togrow
growand
waste andinin2019
continues toamounted
2019 grow andtoin
amounted to85,425
85,425
2019 PJPJ(Fig-
(Fig-
amounted
ure85,425
to 10) [35]. Energy generation from waste-to-energy systems
Energy generation from waste-to-energy systems is reported to have
PJ (Figure 10) [35]. Energy generation from waste-to-energyis reported
systems to have
is in-
reportedin-
creased
to from 221
have increased TWh
from in 2010
221 TWhto 283
in TWh
221 TWh in 2010 to 283 TWh in 2022 [36].
2010 toin 2022
283 TWh[36].
in 2022 [36].

60
60
50
waste-to-energy

50
worldwide
Forecastwaste-to-energy
valueworldwide

40
40
billion]
[USDbillion]

30
30
marketvalue

20
20
[USD
Forecast

10
market

10
0
0
2019 2020 2021 2022 2023 2024 2025 2026 2027
2019 2020 2021 2022 2023 2024 2025 2026 2027
Year
Year
Figure 8. Global
Global waste-to-energy market
marketvalue
valueforecast
forecast(2019–2027)
(2019–2027)[33].
Figure 8.
Figure 8. Global waste-to-energy
waste-to-energy market value forecast (2019–2027) [33].
[33].

3
3
waste
productionofofwaste

2.5
2.5
[EJ]

2
energy[EJ]

2
production

1.5
energy

1.5
1
1
forfor
Global

0.5
Global

0.5
0
0 2000 2005 2010 2015 2016 2017 2018 2019
2000 2005 2010 2015 2016 2017 2018 2019
Energies 2023, 16, x FOR PEER REVIEW Production year 8 of 26
Production year
Figure 9.
Figure 9. Global
Global production
production of
ofwaste
wastefor
forenergy
energy(2000–2019)
(2000–2019)[34].
[34].
Figure 9. Global production of waste for energy (2000–2019) [34].
90,000
Total energy supply from renewables and waste [PJ]

80,000

70,000

60,000

50,000

40,000

30,000

20,000

10,000

00
1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

Year
Figure
Figure 10.10.Global
Globaltotal
totalenergy
energy supply
supply from renewables
renewablesand
andwaste
waste[35].
[35].

In the current energy crisis, clean energy is a great opportunity for economic growth
in many countries, creating new jobs as well as the development of new international eco-
nomic competition. By 2030, global investments in clean energy have been planned at the
level of approx. USD 2 trillion, which is double compared to the current state of 2022 (Fig-
ure 11). It is estimated that the annual growth of solar and wind energy in the United
States will increase by two and a half times and the production of electric cars by seven
times. In China, the expansion of clean energy is planned, which means a gradual reduc-
tion in the consumption of coal and oil. The current energy crisis in the European Union
 Total en
10,000

00

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019
Energies 2023, 16, 1783 Year 8 of 25

Figure 10. Global total energy supply from renewables and waste [35].

In the current energy

In energy crisis,
crisis,clean
cleanenergy
energyisisaagreat
greatopportunity
opportunity forfor
economic
economic growth
growth
in many
in many countries,
countries,creating
creating newnew jobs as well
jobs as the
as well as development
the development of new ofinternational
new internationaleco-
nomic competition.
economic competition. By 2030,
By 2030,global investments
global in clean
investments energy
in clean have been
energy have planned
been plannedat the at
level
the of approx.
level USDUSD
of approx. 2 trillion, whichwhich
2 trillion, is double compared
is double to the current
compared state ofstate
to the current 2022 of (Fig-
2022
ure 11).11).
(Figure It isItestimated
is estimated thatthat
thethe
annual
annual growth
growth of solar andand
of solar windwindenergy
energyin in
thetheUnited
United
States will
States will increase
increase byby two
two andandaahalfhalftimes
timesand andthetheproduction
productionofofelectric
electriccars byby
cars seven
seven
times. In
times. In China,
China, thethe expansion
expansion of of clean
clean energy
energy isisplanned,
planned,which
whichmeansmeansaagradual
gradualreduction
reduc-
tion
in theinconsumption
the consumption of coal
of coal andand oil. oil.
TheThe current
current energy
energy crisis
crisis in in
thethe European
European Unionhas
Union
has become
become a stimulus
a stimulus for for
the the implementation
implementation of of renewable
renewable energysources,
energy sources,which
whichmay may be
be associated
associated with with a reduction
a reduction in demand
in demand forfor natural
natural gasgas
and and
oil oil
by by20%20%and and
forfor
coal coal
byby
50%.
50%.
In In Japan,
Japan, a green a green transformation
transformation program program
is beingis being implemented,
implemented, ensuringensuring an in- in
an increase
crease infor
funding funding
greenforand green
cleanand cleantechnologies,
energy energy technologies,
includingincluding
nuclearnuclear
energy,energy, low-
low-emission
emission hydrogen,
hydrogen, and ammonia. and ammonia.
In India, In due India, due
to the to the growing
rapidly rapidly growing
demanddemand for elec-
for electricity, it is
tricity, it is planned to achieve the production of clean renewable
planned to achieve the production of clean renewable energy at the level of 500 gigawatts energy at the level of
500
in gigawatts
2030 [37]. in 2030 [37].

2.5
Advanced economies China Emerging and developing economies
Clean energy investment [USD

2
0.5
1.5
trillion]

0.6
0.2
0.2 0.2
1 0.2
0.2 0.2 0.2 0.4
0.3 0.4 0.4
0.3 0.3 0.3
0.5 1
0.6 0.6 0.6 0.7
0.5 0.5 0.5
0
2015 2016 2017 2018 2019 2020 2021 2030
Investment year

Figure 11.
Figure 11. Global clean
clean energy
energy investment
investmentininthe
theperiod
period2015–2021
2015–2021and
andforecasts forfor
forecasts 2030 [37].
2030 [37].

3. Classification, Types, and Sources of Biomass

Due to the origin, function, and final products, biomass can be divided into biomass
existing in nature and the use of biomass as feedstock. The most commonly used clas-
sification is the division of biomass into different groups: wood and woody biomass,
herbaceous biomass, aquatic biomass, animal and human waste biomass, and biomass
mixtures (Tables 1 and 2) [38,39]. Other literature reports indicate that the main sources
of biomass (Figure 12) include agricultural and forest residues (waste from the wood in-
dustry, e.g., sawdust, shavings, etc.), animal residues, sewage, algae, and aquatic crops.
Biomass also includes municipal solid waste (MSW) and waste streams originating from
anthropogenic activities in the absence of the possibility of their reuse [9].

Table 1. Types of biomass and examples [38].

Type of Biomass Species and Varieties

Wood industrial waste, forest waste, branches, stems, chips,
Wood and woody biomass foliage, lumps, pellets, briquettes, sawdust, bark, sawmill, and
others from various wood species
Flowers and grasses (bamboo, brassica, timothy, alfalfa,
miscanthus, switchgrass, cane, arundo, bana, cynara, others);
straws (sunflower, mint, bean, barley, flax, oat, sesame, wheat,
Herbaceous biomass
corn, rice, rape, rye, others); other residues (husks, fruits,
grains, vegetables, coir, pips, cakes, bagasse, fodder, pits,
hulls, pulps, kernels, seeds, shells, stalks, cobs, food, etc.)
 Energies 2023, 16, 1783 9 of 25

Table 1. Cont.

Type of Biomass Species and Varieties

Freshwater or marine algae, microalgae or macroalgae, kelp,
Aquatic biomass
lake weed, seaweed, water hyacinth, etc.
Animal and human waste
Various manures, meat-bone meal, bones, etc.
biomass

Table 2. Range of chemical composition of different types of biomass [39].

Volatile Fixed
Moisture
Type of Biomass C [%] O [%] H [%] S [%] N [%] Matter Carbon Ash [%]
[%]
[%] [%]
Wood and woody
49–57 32–45 5–10 <1–1 <1–1 30–80 6–25 5–63 1–8
biomass
Herbaceous
42–58 34–49 3–9 <1–1 <1–3 41–77 9–35 4–48 1–19
biomass
Aquatic biomass 27–43 34–46 4–6 1–3 1–3 42–53 22–33 8–14 11–38
rgies 2023, 16, xand
Animal FOR PEER REVIEW
human
57–61 21–25 7–8 1–2 6–12 43–62 12–13 3–9 23–34
waste biomass
Biomass mixtures 45–71 16–46 6–11 <1–2 1–6 41–79 1–15 3–38 3–43

Figure 12. The main biomass sources [9].

Figure 12. The main biomass sources [9].
Wood biomass consists mainly of cellulose (CE), hemicellulose (HCE), and lignin (LIG).
Most often, these are wood and furniture industry waste, tree and root residues, bark, and
leaves Wood
of woodybiomass
shrubs, fromconsists mainly
which energy can beof cellulose
obtained (CE),
as a result hemicellulose
of combustion,
(LIG). Most
gasification, often,
or other these
thermal are wood
conversion and
processes. furniture
Production industry
residues, waste, tree
non-commercial
bark, and leaves of woody shrubs, from which energy can be obtained
wood residues, post-consumer wood waste, municipal, and agricultural waste are often
used for energy purposes [38].
bustion, gasification, or other thermal conversion processes. Produc
commercial wood residues, post-consumer wood waste, municipa
waste are often used for energy purposes [38].
Herbaceous biomass resources come mainly from agricultural r
Energies 2023, 16, 1783 10 of 25

Herbaceous biomass resources come mainly from agricultural residues and energy
crops. Agricultural residues are by-products of food, textile, and other industries. Some
of these wastes are used as animal feed. Their use as a source of bioenergy is not yet
sufficiently known because their monitoring is not sufficient and there is a lack of studies
in this area. On the other hand, energy crops are used for energy purposes [10].
Aquatic biomass includes macroalgae, microalgae, and emerging plants. Macroalgae
are multicellular organisms that can reach up to tens of meters in length. They are mainly
used in food production and hydrocolloid extraction. Microalgae are microscopic organisms
such as diatoms, green algae, and golden algae. They are one of the largest sources of
biomass on earth. They can be used to obtain starch, oils, or carbohydrates. Emerging
plants occur partially submerged in swamps and marshes [40]. Aqueous biomass is a very
good raw material for the production of biodiesel due to the fact that much larger amounts
of biomass material per hectare can be used compared to land-based crops. However, the
commercialization of biofuel from aquatic biomass is a huge challenge and requires a lot of
technological research before successful implementation [41].
Sources of animal and human waste include various types of animal manure, human
dung, meat meal, and bones. This waste is a source of pollution, unpleasant odors, and a
threat to health; hence the relevant regulations have ordered the introduction of appropriate
management methods. A useful technique is anaerobic digestion, which produces biogas
as a potential source of energy in households or a source of electricity in power plants or
internal combustion engines [42]. Sometimes biomass waste is in a mixed form, consisting
of many raw materials of different types (Table 3).

Table 3. Higher heating values (HHV) of biomass waste samples.

Biomass Waste/Ref. HHV [MJ/kg] Biomass Waste/Ref. HHV [MJ/kg] Biomass Waste/Ref. HHV [MJ/kg]
Corn stover [43] 17.8 Sugarcane bagasse [13] 20 Sugarcane leaves [13] 20
Corncob [43] 17.0 Sunflower shell [43] 18.0 Banana peel [13] 17.4
Beech wood [43] 19.2 Barley straw [13] 18.16 Ailanthus wood [43] 19.0
Wheat shoot [13] 17.15 Hazelnut shell [43] 20.2 Wood bark [43] 20.5
Olive husk [43] 20.9 Walnut shell [43] 21.6 Wood chips [44] 20.9
Bagasse [44] 21.2 Straw [44] 15.2 Rice husk [44] 15.1
Pine bark [44] 20.4 Cotton stalks [44] 19.0 Black coffee husks [44] 18.6
Pine sawdust [45] 18.3 Tucuma seed [45] 20.8 Ground nut shell [46] 19.7
Soya stalk [46] 19.1 Saw dust [46] 17.7 Palm frond [46] 14.5
Press mud [46] 14.9 Forest leaves [46] 12.2 Palm leaves [46] 15.4
Bamboo leaves [47] 15.7 Coconut husk [47] 15.9 Elephant grass [47] 15.1
Typha [47] 15.8 Castor stalk [47] 14.6 Ipomea [47] 15.3
Sunhemp [47] 15.9 Sesbania [47] 14.4 Bringle residue [47] 12.3
Tomato residue [47] 11.3 Capsicum residue [47] 13.0 Kanjaru weed [47] 9.8
Su baval [47] 16.8 Perry grass [47] 14.5 Okhara residue [47] 12.4
Eucheuma Algae powder
8.9 Spirullina powder [47] 19.5 5.1
seaweed [47] Spirogyra [47]

Generally speaking, sources of biomass waste for biofuel purposes may be agriculture,
forestry, the agrifood industry, public utility facilities, and others. The content of the natural
components (cellulose (CE), hemicellulose (HCE), and lignin (LIG)) varies depending on
the type of biomass; examples include the following: wheat straw (38% CE, 30% HCE,
16.5% LIG), rice straw (39.04% CE, 20.9% HCE, 5.7% LIG), rice hull (33.47% CE, 21.03%
HCE, 18.8% LIG), soft timber (35–40% CE, 25–30% HCE, 27–30% LIG), soybean hull (56.4%
CE, 12.5% HCE, 18% LIG), rye straw (28.8% CE, 27.6% HCE, 2.8% LIG), sorghum straw
(32% CE, 24% HCE, 13% LIG), barley straw (40% CE, 30% HCE, 15% LIG), peanut shell
(40.5% CE, 14.7% HCE, 26.4% LIG), sugarcane bagasse (65% CE and HCE, 18.4% LIG),
maize stover (12.4% CE, 30.8% HCE, 1.4% LIG), coconut husk (24.7% CE, 12.26% HCE,
40.1% LIG), rapeseed straw (32% CE, 16% HCE, 18% LIG), soybean straw (35% CE, 17%
HCE, 21% LIG), sunflower straw (32% CE, 18% HCE, 22% LIG), energy plants (45% CE,
Energies 2023, 16, 1783 11 of 25

30% HCE, 15% LIG), grasses (39.7% CE, 16.9% HCE, 17.6% LIG), wood waste (50% CE, 23%
HCE, 22% LIG), and municipal waste (45% CE, 9% HCE, 10% LIG) [48–58].
Non-fossil, organic materials of biological origin constitute solid biomass that can be
used to produce electricity and heat. Examples include firewood (e.g., pellets or briquettes
produced from wood and paper industry waste and natural plant waste), energy crops
grown on plantations, for instance, grasses (Panicum virgatum, Andropogon gerardi, Miscant-
hus giganteus, reed canarygrass, etc.), fast-growing trees and shrubs (Acer negundo, Robinia
pseudoacacia, willow, poplar, Rosa multiflora, etc.), perennials (Sakhalin knotweed, Jerusalem
artichokes, Virginia mallow, Silphium perfoliatum, etc.), annuals (energy crops: rye, beet, maize,
rape), as well as residues from horticulture and agriculture [48]. Another classification
includes the following division: processed waste (e.g., fruits and vegetable waste, sawmill
wastes, plant oil cake, nutshells and flesh, bagasse, industrial wood waste), processed
fuel (e.g., biogas, densified biomass, charcoal waste, briquette, pellets, plant oils, rape,
sunflower, methanol, ethanol), woody biomass (e.g., wood waste, shrubs, bushes, forest
floor, sweepings), non-woody biomass (energy crops, cereal straws, cassava, cotton, roots,
tobacco, stems, grasses, and soft plant stems) [59].
The cultivation of energy crops is becoming an increasingly popular source of energy.
The requirements are similar to those for agricultural crops, namely the right type of soil,
climatic conditions, agronomic procedures, and others. In 2019, the global production
volume of the most popular energy crops was as follows: wheat 733.4 million metric tons
(MMT), coarse grain 1373.6 MMT, and rice 484.2 MMT. Their largest producers include
China, India, and the United States [13].
There are six categories of crop groups with their residues: cereal (rice straw and husk,
wheat shoot and pod, maize cob and shoot, bajra cob, husk and shoot, barley straw, ragi
straw, and jowar cob, husk, and shoot), oilseeds (shoots of mustard, rapeseed, sesame,
Niger, linseed, safflower, and groundnut), pulses (shoots of sunflower, tur, lentil, gaur, and
gram), sugarcane (bagasse and leaves of sugarcane), horticultural (banana peel, coconut
frond, and areca nut husk and frond), and others (cotton and jute shoots, husks, shells).
Unfortunately, in developing countries, some farmers practice burning crop residues in
their fields, wasting energy that could be used for energy purposes for many people [60].
According to the Food and Agriculture Organization (FAO), forest resources in terms
of biomass are only considered in the range of material diameters equal to or greater
than 10 cm. The following types of residues can be included in this category: processed
forest residues (sawdust and logs) and unprocessed residues (trees, branches, and leaves).
According to FAO statistics, about 25% of the world’s forest land is about 5 billion hectares
of forested land [61,62].
Municipal solid waste accounts for a huge amount of waste from urban and rural
areas around the world. These include household waste, medical waste, or industrial waste,
which are sometimes not all sorted, so they are stored in the same landfill. In order to
be subjected to appropriate thermal, chemical, or biochemical processes, segregation is
necessary. Then, it is possible to use the waste in a sustainable way to convert it into energy
within the framework of a circular economy [63].
Inadequate and irresponsible management of solid waste may lead to increased
pollution of the land, water, and air environment. The consequences for humanity can be
catastrophic and related to the uncontrolled spread of many pathogenic microorganisms
and, thus, the deterioration of public health (chronic, infectious diseases of the respiratory or
digestive system). In addition, landfilled solid waste can produce huge amounts of methane,
which contributes to significant emissions of greenhouse gases into the atmosphere as a
result of global climate change. Therefore, in order to prevent the negative effects of the
growing amount of solid waste, solutions such as segregation and recycling, combustion in
boilers to produce heat and electricity, anaerobic digestion to produce compost, bioenergy,
or electricity should be sought and implemented [64].
Energies 2023, 16, 1783 12 of 25

According to the literature on the analysis of global solid waste management, there
has been a significant increase in the amount of waste generated annually in recent years.
At the current rate of growth, it is estimated that the amount of waste could reach around
2.2 billion tons per year in 2025, and the costs could rise to around £302.67 billion [65].
Another group of biomass materials is those used to remove pollutants from the
aquatic environment. Appropriate quality drinking water is a prerequisite for the proper
and sustainable development of life and ecosystems. The natural nature of water is chang-
ing, and access to clean and healthy drinking water has become an issue in many emerging
and developing countries. Water pollution is related to climate change but also to human
activities, including intensive and rapid industrialization, urbanization, uncontrolled con-
sumerism, water pollution from industrial wastewater, and household waste [66–69]. In
accordance with the UN World Water Development Report (2018), nearly 47% of the global
population lacks access to clean and reliable drinking water, and pursuant to estimates,
this number may increase to 57% in 2050 (approx. 4 to 10.2 billion people) [70]. Large
amounts of water are used by industrial plants, and after processing, contaminated water
is discharged into land reclamation or rivers, causing pollution and a threat to aquatic
life. Among the contaminants, there are often heavy metals that come from various in-
dustries, including mining, tanneries, untreated municipal sewage sludge, electroplating,
industrial production such as textiles, smelters, foundries, dyeing, metallurgy, alloy in-
dustry, petrochemical plants, oil refineries, metal plating, chemical industry, chemical
fertilizers, pesticides, radiator manufacturing, battery manufacturing, as well as metal
piping, transport, fuel combustion, combustion by-products from coal-burning power
stations, and many others [71]. Heavy metals (Cu, Cd, Zn, Pb, Cr, As, Hg, Ni, Co, etc.)
are estimated to be the main pollutants in wastewater, and they are a threat due to such
properties as non-biodegradability, toxicity, harmfulness to the health of living organisms,
or carcinogenicity. Therefore, it is necessary to remove or reduce metal ions from industrial
wastewater before they enter the aquatic environment (rivers, lakes, seas, oceans, or other
water reservoirs) [72–75].
Among conventional methods, the most promising are adsorption and biosorption
processes due to many benefits such as the low cost of adsorbents (for instance, industrial
waste), low operating costs, simple operation, no need for additional chemical reagents, the
small amount of sludge produced, low energy demand, no negative impact on the natural
environment, high efficiency of the metal removal process, simultaneous adsorption of
many metal ions, treatment of large volumes of wastewater, the possibility of adsorbent and
biosorbent regeneration, the possibility of easy desorption of metals, being functional in a
wide range of process conditions, including temperature, pH, concentration and presence
of other metal ions, adsorbent dose, the reduction in the amount of waste, the possibility
of metal removal in dilute concentrations at ppb level, and no increased chemical oxygen
demand of water, which is a limitation of some conventional methods [76]. Appropriate
adsorbents and biosorbents are selected on the basis of previously conducted laboratory
experiments or literature reports. Commonly used commercial adsorbents are activated
carbons, carbon nanotubes, or zeolites. However, the costs of adsorption processes using
activated carbons are high and continue to increase due to the rising prices of fossil fuels
and the depletion of coal-derived activated carbon [77]. Due to these obstacles, cheap
adsorbents with high adsorption capacity and minimal environmental impact are sought.
Of particular interest are raw materials and natural resources, low-cost biomaterials derived
from agricultural by-products, available agricultural waste, terrestrial and aquatic biomass,
as well as by-products of industrial processes. The effectiveness of ecological adsorbents
varies and depends on the composition, process conditions, or type of metal ions. Some-
times biosorbents are highly effective and comparable to expensive commercial ones (e.g.,
composites based on biopolymers), and sometimes their effectiveness is at an average
or low level. However, waste adsorbents from industry and agriculture are certainly an
ecological and economical solution for new technologies for removing heavy metal ions
 Energies 2023, 16, 1783 13 of 25

from wastewater. In addition, secondary raw materials from waste are a valuable energy
source of biomass [78].

4. Biomass Energy Classification and Conversion Methods

The term bioenergy is an increasingly popular term used in the literature and means
energy from various sources of biomass. Current technological progress creates many
opportunities for the implementation of new alternative energy sources. The use of biomass
resources is a promising direction for the management of waste collected daily in huge
amounts in many urban and rural areas. Bioenergy can be produced in the form of heat,
PEER REVIEW 14 of 26
electricity, or biofuels (gaseous, liquid, solid) in thermochemical or biochemical processes
as a result of biomass treatment (Figure 13). In order to produce bioenergy, bioproducts, or
biofuels, pretreatment of biomass is necessary [79–81].

Figure 13. Biomass conversion into bioproducts [79–81].

Figure 13. Biomass conversion into bioproducts [79–81].
Biomass can be converted into such forms of energy as liquid biofuels (methanol,
Biomass can beethanol,
converted into(hydrogen,
etc.), gases such forms of energy
synthesis gas, etc.),as
andliquid biofuels
electricity through(methanol,
biochemical or
thermochemical processes. Vegetable oil, rapeseed, soybean, and waste fats can be used to
ethanol, etc.), gases (hydrogen, synthesis gas, etc.), and electricity through biochemical or
produce biodiesel, while corn or sugar cane can be used to produce bioethanol [82].
thermochemical processes. Vegetable
Bioenergy oil, rapeseed,
production is associatedsoybean,
with varying and waste
degrees of fats canconsumption,
biomass be used
to produce biodiesel, while corn or sugar cane can be used to produce bioethanol [82]. from
depending on its energy characteristics. Thermal energy can be the result directly
Bioenergy production is associated
the combustion with
of biomass, varying
and the degrees
heat generated canofbebiomass consumption,
used to produce steam, which
can provide heat for the production processes of specific products, or it can be converted
depending on its energy characteristics.
into energy by delivering itThermal energy
using a steam can
turbine. be the result
Sometimes directly from
the low characteristics (low
the combustion of biomass, and the
energy density) heat generated
of biomass fuel material can beconversion.
require used to produce
The purpose steam, which
of the conversion
can provide heat for isthe production
to adapt processes
biomass fuels of specific
to the requirements of products,
the high-energyor it can be
density fuelconverted
market, where
into energy by delivering it using a steam turbine. Sometimes the low characteristics (low
energy density) of biomass fuel material require conversion. The purpose of the conver-
sion is to adapt biomass fuels to the requirements of the high-energy density fuel market,
Energies 2023, 16, 1783 14 of 25

traditional gaseous, liquid, and solid fuels are used. In recent years, the wood industry has
provided waste wood biomass for bioenergy production in the amount of almost half of
the total energy supplied to the market [83].
Plant biomass obtained from different areas and changing weather conditions is char-
acterized by increased humidity; hence the drying process is required. Drying of biomass
is carried out before its storage in order to remove moisture and prepare it for further
conversion processes. The first known conversion method is the mechanical processing of
biomass through various processes, such as grinding (chipping, cutting) and next pressing,
pelleting, or briquetting. In order to reduce transport costs and increase bulk density,
biomass is shredded before transport. In turn, solid fuel (e.g., husks, hay, straw, sawdust,
etc.) densification processes are used to improve physical and energy properties. Thanks
to this, the shapes and sizes of converted biofuels to the required standards allow for
distribution in the energy industry [48].
Another method is the thermal conversion of biomass, including pyrolysis, gasification,
carbonization, or combustion. One of the most common and recommended combustion
methods is incineration in fluidized bed boilers, which is highly efficient and allows energy
recovery. Another method is the process of co-combustion of coal with biomass in specific
proportions in boilers intended for coal combustion [84].
Co-combustion of biomass takes place in a furnace chamber in which biomass and
coal are fed as a previously prepared mixture or separately. Indirect co-combustion, on
the other hand, takes place in a gasifier after biomass gasification, and the resulting gas
is transferred to a combustion chamber, where it is incinerated. When biomass and coal
are burned in separate combustion chambers, this is parallel combustion. Thermal car-
bonization of biomass takes place under pressure close to atmospheric pressure and at
higher temperatures (approx. 200–300 ◦ C). As a result of this drying process, biofuel is
obtained with physicochemical properties, such as hydrophobicity, increased calorific value,
energy and physical properties similar to coal, resistance to biological degradation, and
others. Another process is pyrolysis involving the thermal decomposition of biomass in
anaerobic conditions or in a small amount of oxygen. As a result of rapid pyrolysis at high
temperatures (approx. 500 ◦ C), biomass decomposes into syngas and char. After cooling,
an oily liquid with a good calorific value is formed. Slow pyrolysis generates charcoal, char
with increased stability, low humidity, and high energy density. In addition, pyrolysis also
produces pyrolysis oil or gas. Gasification of biomass consists of many thermal processes
to which biomass is subjected in a gasifier. The stages include drying at a temperature
of approx. 150 ◦ C, formation of oxides, CO2 , and water vapor at a temperature above
600 ◦ C (oxidation) and reduction of CO2 and water vapor to CO and H2 . As a result of
biomass gasification processes, the following products are generated: gaseous (wood gas),
liquid (acids, alcohols, steam), tar, and solids (fly ash). Biochemical methods include the
transesterification of animal fats and vegetable oils for the production of biodiesel, as well
as anaerobic fermentation for the production of alcohols (e.g., methanol, ethanol) or biogas.
Biomass components such as cellulose, hemicellulose, and lignin are converted into liquid
fuel in subsequent processes into methanol, ethanol, or biogas [84].

5. Energy Aspects of Biomass

Biomass waste can potentially be used as an energy source in connection with the
current trends in the demand for renewable energy sources [85]. In accordance with
Directive 2001/77/EC, biomass is defined as “the biodegradable fraction of products,
waste and residues from agriculture (including vegetal and animal substances), forestry
and related industries, as well as the biodegradable fraction of industrial and municipal
waste” [86]. Other sources say that biomass is characterized as any organic matter of
plant or animal origin, as well as materials obtained as a result of their transformation or
processing [87,88]. The energy potential of biomass depends on the form of fuel, type of
material, moisture content, or calorific value [48]. In addition, its positive value results
from the quantity, availability, chemical composition, acquisition, and processing costs.
Energies 2023, 16, 1783 15 of 25

Biomass can be used for direct combustion or co-combustion in solid, liquid, or gaseous
form. Biofuels derived from it can include pellets, wood shavings, firewood, various fruit
stones, and nut shells. Wood chips can come from the processes of shredding forest and
agricultural waste. Pellets have the appearance of small cylinders with a diameter of up
to several millimeters and a length of several tens of millimeters. They are formed as a
result of pressing biofuels with binding additives [43,89,90]. Pellets are an increasingly
popular form of renewable energy due to the fact that they are considered ecological,
economical, and available on the local market. They are pure, natural products obtained
from plant stems, waste materials, straw, wood chips, processed sawdust, post-production
waste, or agricultural food waste. The positive aspect is the fact that no chemicals are
added to pellet production processes, and natural substances are used as binders when
forming the round cylindrical shape, e.g., pectin of plant fiber or lignin contained in
wood. Other advantages include the use of only natural and renewable raw materials for
pelletization, no additional CO2 emissions due to the introduction of ecological circulation
of raw materials, high functionality of fuel combustion, and low costs of the pelletization
process. Pellets formed as a result of carbonization are characterized by high energy density,
higher hydrophobicity, resistance to moisture, better grinding properties, and greater
resistance to biological degradation [91]. Unfortunately, biomass combustion also brings
with it various operational problems, including the large number of volatile components
released, which can cause the emission of organic and organochlorine compounds (e.g.,
dioxins, polycyclic organic hydrocarbons), high chlorine content causing corrosive damage
to heating installations and HCl emission, high content of alkali metal oxides in fly ash
causing the formation of deposits and smearing of heating surfaces, the low calorific value
of biomass compared to fossil fuels, low biomass density hindering storage, transport,
feeding to heating devices and adversely affecting the stability of the combustion process,
variable humidity causing additional drying costs, and investment costs related to the
purchase of biomass combustion boilers of special design [92]. An opportunity to reduce
investment costs is the solution of mixing coal with biomass in the co-combustion process.
Thanks to this, there are lower costs associated with the purchase of traditional fuel, a
reduction of emission fees, and the possibility of using low-cost biomass. In addition,
co-combustion can be carried out in grates, pulverized beds, and fluidized bed boilers,
both of high and low power. The effectiveness of the co-combustion process depends on
the proper selection of the proportions of the fuel composition components. It should be
emphasized that the proportions depend on the properties of the specific biomass, and the
maximum share of biomass in the composition should not exceed 30% [93].
Biomass is ecologically clean fuel, which means, among other things, that it does
not contribute to the emission of excessive amounts of CO2 . Taking into account the
overall balance, the CO2 emission is taken as zero if only the amount of CO2 emitted from
combustion that will be assimilated in the process of plant growth is taken into account.
Ecological purity is related to the situation when the emission of CO2 in the combustion
process is equal to its absorption during the renewal of biomass through photosynthesis.
The overall balance should take into account energy flow in the whole cycle involving
incineration or co-incineration processes [94].
It has been shown that biomass waste has a high energy potential and a higher heating
value comparable to commercial fuels (for instance, the calorific value of coal is estimated
in the range of 25–35 MJ/kg [95]) (Table 3). The global production of these by-products has
a growing trend, which makes them attractive and competitive not only for the generation
of heat and electricity but also for reducing carbon dioxide emissions into the atmosphere.
Biomass waste, which is a potentially renewable source of energy, contains energy
polysaccharide components; however, differences between individual materials occur in
the elemental, chemical composition, and biomass energy capacity. The main measure of
energy efficiency of biofuel is its calorific value, expressing the dependence of chemical
composition on elementary components. Lowering calorific value is affected by moisture
and ash content. Therefore, in order to obtain reliable results comparing the energy potential
Energies 2023, 16, 1783 16 of 25

of biomass, the state of dry matter should be taken into account. Energy potential is
determined on the basis of net calorific value (NCV) and gross calorific value (GCV). GCV
refers to the amount of energy released (per unit volume or mass) during the stoichiometric
combustion of a material. Generally speaking, the higher GCV, the more efficient the
combustion process. Assessment of the energy properties of materials is necessary when
estimating the use of biomass waste as a potential source of renewable energy. By knowing
these properties, biomass production yields can also be optimized and product quality
improved. The following properties should be determined: basic density [kg/m3 ], ash
and volatile matter content [%], solid carbon content [%], moisture content [%], moisture
absorption capacity [mg/g], particle size [nm] and shape, resistance to processing, calorific
value [MJ/kg], the heat of combustion [MJ/kg], the content of ash and combustible sulfur
[%], and the content of hydrogen, nitrogen, oxygen, and chlorine [%] [96]. Energy density
is calculated from the relationship between the gross calorific value and the material’s basic
density, according to Equation (1):

( GCV )
BED = ÷ 1000 (1)
Bd

where BED = basic energy density [GJ/m3 ], GCV = gross calorific value [MJ/kg], Bd = basic
density [kg/m3 ] [25].
In order to determine the volume of emissions of individual gases and dust from
renewable energy sources, the method of emission factors is used. The emission can be
determined according to Equation (2):

Emission = A· EF (2)

where A = activity [Mg], EF = emission factor [kg/Mg].

The amount of fuel burned per hour can be determined according to Equation (3):

3600· NP
B= (3)
η ·CV

where B = fuel consumption [kg/h], NP = nominal boiler power [kW], η = combustion

efficiency, CV = calorific value [kJ/kg].
In food processing plants, pollution abatement equipment is used for the amount of
dust. Hence, a dust drift factor that corresponds to an emission factor can be used. The CO
emission factor can be calculated from Equation (4):

28
EFCO = · EFC ·(C_CO/C ) (4)
12
where EFCO = carbon monoxide emission factor [kg/kg], 28/12=the ratio of molar masses
of carbon monoxide and carbon, EFC = emission factor of chemically clean coal [kg/kg],
C_CO/C = part of the carbon emitted as carbon monoxide (average value of 0.06 can be
assumed for agricultural waste).
EFC = c· pc (5)
where c = carbon content in biomass in working condition [kg/kg], pc = part of coal oxidized
in a combustion process (for agricultural waste, the average value can be taken as 0.88)
CO2 emission factor can be calculated from Equation (5), taking into account the total
carbon balance:
 
44 12 12 26.4
EFCO2 = · EFC − · EFCO − · EFCH4 − · EFN MVOC (6)
12 28 16 31.4

where EFCO2 = CO2 emission factor [kg/kg], 44/12=the ratio of molar masses of carbon
dioxide and carbon, 12/28 = the ratio of molar masses of carbon and carbon monoxide,
12/16 is the ratio of molar masses of carbon and methane, EFCH4 = CH4 emission factor
Energies 2023, 16, 1783 17 of 25

[kg/kg], EFNMVOC = emission factor of volatile organic compounds (except CH4 , value for
field and orchard yields can be assumed to 0.009 and 0.004, respectively).
CH4 emission factor can be calculated based on Equation (7):

16
EFCH4 = · EFc ·(C_CH4 /C ) (7)
12
where EFCH4 = CH4 emission factor [kg/kg], 16/12r = the ratio of molar masses of methane
and carbon, C_CH4 /C = part of the carbon emitted as CH4 (average value of 0.005 can be
assumed for agricultural waste).
NOx emission factor is the sum of nitrogen dioxide and nitrogen oxide emission factors
and can be calculated from Equation (8):

46
EFNOx = · EFC ·( N/C )·( N_NOx /N ) (8)
14
where EFNOx = NOx emission factor [kg/kg], 46/14 = the ratio of molar masses of nitrogen
dioxide and nitrogen, N/C = the nitrogen to carbon ratio in biomass, N_NOx /N = part of
the nitrogen emitted as NOx (average value of 0.122 can be assumed for agricultural waste).
SOx emission factor is the sum of SO2 and SO3 emission factors and can be calculated
from Equation (9):
2S
EFSO2 = ·(1 − r ) (9)
100
where EFSO2 = SO2 emission factor [kg/kg], 2 = the ratio of molar masses of SO2 and sulfur,
S = sulfur content in fuel [%], r = coefficient determining the proportion of total sulfur
remaining in fly ash.
The amount of fly ash lifted over the furnace depends on the conditions of the combus-
tion process. It is estimated that 30% of ash generated is fly ash raised above the furnace in
the case of hard coal combustion for a mechanical grate and steam output of ≥20 Mg/h.
However, in the case of co-combustion of conventional fuel with the addition of biomass
waste, the value of 15% to the fly ash removal from ash generated can be used to determine
the dust emission factor. Dust emission factor for coal and biomass can be calculated from
Equation (10):
100 − η0
EFdust = 1.5·CFA · (10)
100 − k
where 1.5 = the coefficient representing 15% ash lift in the form of fly ash, CFA = fly ash
content in fuel [%], (1.5 · CFA ) = drift indicator determining the amount of dust generated
during combustion [kg/Mg], η 0 = dedusting efficiency (assumed 20%), k = the content of
combustible parts in the dust (assumed 25% for coal and 5% for biomass).
The emission of gases and dust is directly proportional to the content of fly ash
and sulfur in a fuel mass unit. The calorific value of fuel should be taken into account
when estimating emissions per unit of energy. The emissions of sulfur dioxide, nitrogen
dioxide, carbon monoxide, carbon dioxide, and dust can be determined from the following
Equations (11)–(15):
ESO2 = B·16·S (11)
ENO2 = B·1 (12)
ECO = B·100 (13)
ECO2 = B·1850 (14)
100 − η0
ED = B·1.5·CFA (15)
100 − k
where ESO2 = SO2 emission [kg/h], B = fuel consumption [kg/h], S = sulfur content in fuel
[%], ENO2 = NO2 emission [kg/h], ECO = C O emission [kg/h], ECO2 = CO2 emission [kg/h],
Energies 2023, 16, 1783 18 of 25

ED = dust emission [kg/h], CFA = fly ash content [%], η 0 = dedusting efficiency (assumed
20%), k = content of combustible parts in the dust (assumed 25% for coal).
From an ecological point of view, an important component of biomass fuel is sulfur. In
fuel combustion processes, sulfur is transformed into sulfur oxides, which are emitted into
the atmosphere and pollute the environment, as well as irritating the respiratory system
of animals and humans. Hence, the determination of sulfur content is one of the basic
analyses of biomass for fuel, and the result gives toxicological information and information
about the possible impact on the environment. During combustion, nitrogen is converted
into nitrogen oxides (NOx ), which are released into the atmosphere. High concentrations of
NOx are toxic and irritating to the respiratory system. The sulfur and nitrogen content in
coal varies and depends on the type and origin, but most often, it ranges from 0.5% to 5%
of total sulfur [97] and from 0.5% to 2% of total nitrogen, respectively [98]. On the other
hand, S and N content in biomass waste is considered low and, according to the literature,
examples are as follows: coffee husk (0.67% S, 1.55% N), rice husk (0.59% S, 0.31% N) [46],
burley stalk (0.55% S, 0.89% N), Virginia stalk (0.48% S, 0,85% N), corn cob (0.1% S, 0.4%
N), corn stalk (0.05%S, 1.28% N), wheat straw (0.1% S, 1.65% N), sunflower stalk (0.12% S,
2% N), barley stalk (0.06% S, 0.41% N), and oat stalk (0.11% S, 0.69% N) [99].

6. Barriers to the Use of Biomass Materials

In most literature studies, opinions about the positive aspects of using biomass can be
found, and indeed this direction should still be developed. However, these are materials
with different characteristics and physicochemical properties than crude oil, hard coal, or
lignite; hence there may be various barriers or challenges during their operation. Firstly, the
high moisture content of biomass makes it unsuitable for thermal conversion processes such
as pyrolysis or gasification, as it significantly reduces its efficiency. In addition, biofuels
obtained as a result of conversion may contain moisture, which is naturally undesirable
in combustion processes. Therefore, to increase a calorific value, pre-drying should be
carried out. Unfortunately, the drying process is associated with additional high costs and
energy input. High moisture content affects biological degradation, the development of
fungi, mold, bacteria, and other microorganisms, as well as the loss of organic substances.
The disadvantage of high water content can be solved by densifying the material in press-
ing processes. Increasing bulk density reduces storage capacity and transport costs, but
unfortunately, the compaction process itself generates additional costs. Sometimes high
moisture content is beneficial, for example, in hydrothermal conversion processes during
the production of alcohol from carbohydrates with the use of hydrolysis and fermentation
of biomass. Then water is an important reagent during the conversion [100,101].
Another disadvantage is the bulk density of biomass, which is mostly low, and for
woody and grassy biomass, it is usually in the range of 160–220 kg/m3 and 80–150 kg/m3 ,
respectively. As a result, there are difficulties in exploiting large amounts of biomass, and
higher storage and transport costs [102]. Densification by mechanical pressing is used to
increase bulk density. Cubing, pelleting, or briquetting are used to give uniform shapes
and dimensions. Thanks to these processes, it is possible to increase the density of biomass
materials many times, depending on its type, moisture, properties, densification technique,
etc. The costs of storage, transport, and handling can be significantly reduced [103].
The proportions between cellulose, hemicellulose, and lignin in the composition are
different for different types of biomass. For example, hardwood biomass contains more
cellulose, and hemicellulose has D-xylose structures such as arabinoglucuronoxylan. Straw,
on the other hand, has more hemicellulose. Such diversity in the composition of biomass
materials has an impact on the fact that the technology of their conversion to the production
of biofuels and other products must be properly designed to ensure the maximization of
the efficiency of these processes [104]. The possibility of effective use of biomass depends
on its physicochemical properties, methods of initial preparation, or optimization of the
conditions of the production process. The diversity in the composition affects the initial
preparation and, in subsequent stages, the dissolution of biomass. Properties such as the
Energies 2023, 16, 1783 19 of 25

hydrophobicity of lignin, crystalline arrangement of cellulose, location of cellulose in the

hemicellulose–lignin zone, and difficulties in cleaving hydrogen, ether, and other bonds
make biomass materials resistant to dissolution. Cellulose is difficult to hydrolyze because
it is contained in a lignin matrix. These barriers mean that biomass should first be broken
down into lower molecular weight substances in order to be processed into various prod-
ucts. Then, hydrolysates from shredded biomass can be used for the production of solvents,
sugars, sugar alcohols, or biofuels such as hydrogen, ethanol, methanol, etc. However,
hydrolysis processes are also burdensome for the environment because toxic chemicals
such as mineral acids and hydroxides are used, or the process is lengthy in the case of
enzymatic hydrolysis [101,105]. In addition, obtaining glucose from biomass sometimes
requires high-temperature conditions or high concentrations of acids. In turn, at high
temperatures, by-products (tar) are formed during pyrolysis and other processes. The use
of concentrated acids generates higher energy consumption, affects the corrosion of the
installation, requires chemical neutralization, and causes the formation of by-products.
Hydrolysis processes are time-consuming and generate high costs. An additional disadvan-
tage is the fact that under difficult dissolution conditions, carbohydrates may be degraded.
An alternative environmentally friendly solution may be the hydrolysis of biomass using
subcritical water obtained under changed conditions of temperature and pressure [101].
The demand for electricity and heat is constant throughout the year, while the avail-
ability of different types of biomass materials is only seasonal. Perennial energetic plants
(e.g., kenaf, miscanthus, miscanthus, etc.) are available for longer periods, do not require
annual replanting, and their growth does not require specialized and high maintenance and
investment expenditures. On the other hand, food crops (e.g., sugar beet, sugar cane, corn,
etc.) are seasonal and require favorable climatic conditions, fertilization, or other types of
care. The advantage is that the remains of agricultural biomass, such as pulp, peelings,
rice husks, wheat, rye, and corn straw, etc., are a low-cost waste materials, because no
additional land is required for their cultivation. Another valuable source of energy is forest
biomass waste; however, their harvesting and transport generate additional high costs. The
above-mentioned barriers to the use of biomass materials for energy and product purposes
have a negative impact on the success and development of this sector. However, in order
to reduce all these obstacles, new solutions should be sought, including, for example,
standardization systems [101].

7. The Future Scope of Biomass Waste Energy Source

It is inevitable that industry will continue to develop and it is difficult to predict its pace
and direction of development, as well as the consequences for the natural environment
and humans. Among all these unknowns, it is certain that agricultural and industrial
waste will continue to be generated, which requires appropriate and useful management.
Recent years of research have proven that the use of biomass waste for energy purposes
is a promising and innovative direction of development, using environmentally friendly
technologies that reduce the emission of harmful substances and are neutral in terms of
carbon dioxide emissions. Such biomass materials as wood, forest residues (sawdust,
branches, wood pellets), perennial grasses, post-production waste, or landfill gases can be
a valuable source of energy, heat, and liquid fuels. The main benefit is that biomass cannot
be exhausted, unlike fossil fuels. This feature makes renewable energy from all biomass
sources inevitable [10,85,106].
The currently available biomass conversion technologies are diverse due to the goals
to be achieved, such as reducing the impact on the environment and climate change,
the use of individual types of biomass waste resources, or economic efficiency. Thermal
conversion of biomass waste into products, electricity, or heat is mainly achieved through
such processes as combustion, pyrolysis, gasification, fermentation, or transesterification.
Direct combustion of biomass in the presence of air with oxygen is used to generate
electricity and heat. For example, based on research conducted in Pakistan, it was shown
that the use of 70% of rice hulls during combustion generated approximately 1328 GWh
Energies 2023, 16, 1783 20 of 25

of electricity, which was estimated at approximately 47.36 cents/kWh. This is a cheaper

option compared to the cost of generating electricity using coal, which was estimated at
55.22 cents/kWh [107]. According to the literature, the efficiency of electricity production
from burning biomass itself oscillates between 20 and 40% [108]. An opportunity is co-
combustion with coal, which may increase the efficiency of the process. In the near future,
many studies should be carried out to determine the costs and the amount of electricity
generated as a result of the combustion or co-incineration of various types of biomass
waste from various industries and then compare them with the results of the combustion
of conventional fuels. As a result of pyrolysis, i.e., thermal decomposition, bio-char or
bio-oil can be produced, which are the basis for obtaining oxygenated high-octane products,
including diesel oil, kerosene, or gasoline. Thanks to the increased oxygen content, these
biofuels achieve high efficiency during combustion [109]. The next process is gasification,
which consists in converting biomass into a combustible gas mixture consisting mainly of
CH4 , CO, CO2 , and H2 [110]. The resulting hydrogen fuel releases energy and water (H2 O)
during combustion and does not generate greenhouse gases in the atmosphere [111]. It
is known from literature reports that the process of atmospheric oxidation of agricultural
biomass (cereal straw) was used for the chemical production of fuel biogas with a lower
calorific value. Another process concerned the gasification of carbonization pyrolysis,
during which straw tar and charcoal were obtained [112]. A chance potential application
may be gasification using the method of distributed power generation. Unfortunately,
the large-scale application is limited by the high dissipation of energy and the small
volume of biomass waste. Other promising technologies could be supercritical water
gasification (SCWG) for wet biomass and plasma gasification for the treatment of toxic
organic waste [113]. The development of biomass gasification would be more dynamic if
there was greater support from the legislative side, the social environment as well as the
willingness of various investors to invest in order to accelerate commercialization.

8. Conclusions
The issues of increasing pollutant emissions related to human industrial activity, the
use and depletion of conventional fossil fuels, as well as the need to protect the environment,
contribute to the search for ecological renewable energy sources. A significant reduction in
the number of harmful substances emitted to the environment is possible thanks to the use
of biomass for energy purposes. The use of biomass waste as an alternative source of energy
seems to be a real solution, which is already being used effectively by many countries
around the world. Currently, the main use of biomass is the production of biofuels by
mechanical, thermochemical, or biochemical conversion processes. Moreover, it provides
a sustainable fuel source that can gradually replace depleting fossil fuel resources and
minimize the amount of solid waste generated and greenhouse gas emissions. Due to the
fact that the biomass material is diverse and its characteristics depend on local climatic
conditions, each region of the world can look for optimal technological solutions in the
use of its types of biomass for cleaning the aquatic environment from pollutants, including
heavy metals, as well as for conversion into biofuels and then converted into electricity and
heat. In order to effectively and efficiently use biomass waste for energy production, it is
necessary to develop appropriate technology. On the other hand, the use of agricultural
biomass from energy crops can create new prospects for farmers to allocate part of their land
to the cultivation of these crops. The production of bioenergy from agricultural biomass
not only has a positive effect on the natural environment but also generates profits in the
economic and social spheres. New technologies and solutions mean more employment,
revitalize the local economy, and increase farmers’ income. However, the obstacle is still
insufficient knowledge about the energy characteristics of biomass materials found locally
in different regions of the world, insufficient knowledge about the technology of converting
biomass into energy, equipment requirements, installation, efficiency, and many other
obstacles that slow down the development of effective use of biomass in the near future.
Energies 2023, 16, 1783 21 of 25

As a result of the literature research studies, the paper presents:

• An analysis of the cycle of biomass energy,
• biomass availability and the current global energy situation,
• the growing global demand for energy,
• the increasing shift from conventional fossil sources to renewable biomass energy,
• the growing volume of bioenergy production in the world,
• the growing use of waste for energy production,
• the growing total energy supply from renewable energy sources and waste,
• the growing global volume of investment in green energy technologies,
• types and sources of biomass materials,
• benefits of using biomass waste materials,
• the possibility of using various types of waste materials from biomass for the purifica-
tion of the aquatic environment,
• an energy analysis of biomass materials,
• available biomass conversion technologies, including mechanical, thermal and bio-
chemical,
• barriers to the use of biomass materials,
• the future scope of biomass waste energy sources.
The future of obtaining energy belongs to the use of renewable energy sources. Fossil
fuels have limited resources and need to be gradually replaced by other resources such
as agricultural, industrial, and other waste. Their resources will not end, hence they
will require continuous appropriate and useful management. The use of biomass waste
for energy production is a promising direction of development, where the technologies
used reduce the emission of harmful substances into the environment and are neutral in
terms of CO2 emissions. Currently, available technologies are differentiated due to specific
goals to be achieved. These include reducing the impact on the environment and climate
change, the use of specific types of biomass waste resources, or economic and energy
efficiency. Processes such as direct combustion, pyrolysis, gasification, fermentation, or
transesterification are methods of thermal transformation of biomass waste into products,
heat, and electricity. The large variety of biomass materials makes it necessary to conduct
a lot of research on their energy usage, and on determining the costs and the amount of
electricity or heat generated as a result of combustion or co-incineration of various types of
biomass waste from various industries.
According to studies published in the literature, greenhouse gas emissions from the
production and use of biomass turned out to be lower than emissions from coal for elec-
tricity production. Therefore, these ecological premises are one of many strong arguments
justifying the rightness of using biomass as a renewable energy source. This literature
review clearly indicates the need to continue and expand research on the development of
the bioenergy economy sector. In order to accelerate the development of the energy sector
in this direction, legislative changes and appropriate political decisions are necessary.

Funding: This research did not receive a specific grant from any funding agency in the public,
commercial, or not-for-profit sectors.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data is contained within the article.
Conflicts of Interest: The author declares no conflict of interest.
Energies 2023, 16, 1783 22 of 25

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