206
8 Summary
Chapter 3 is focused on waste-to-energy conversion as an advanced method for
waste management. Biomass is introduced as the bio-renewable resource for renewable energy production and the two main methods of biological and thermochemical
conversions are highlighted as the main approaches for biomass conversion. The
technologies, processes and industrial applications of each conversion method are
discussed in detail. The technologies covered in this chapter include combustion,
gasification, pyrolysis, liquefaction, digestion and fermentation. The advantages and
disadvantages of each method are discussed and compared in this chapter. The effectiveness of a specific waste-to-energy process is determined by the thermal potential
of the waste, efficiency of the system and the type of produced energy.
The rest of the chapters of the book are focused on resource recovery from various
waste streams. In Chap. 4, nitrogen and phosphorous recovery from wastewater
streams are discussed. The chapter briefly introduces wastewater production and
treatment levels, sludge production, different types of sludge and their characteristics,
as well as treatment methods, while focusing on recovering nitrogen and phosphorous
as the two main nutrients of interest in wastewater and sewage sludge. Current knowledge on recovering these resources from sludge is reviewed. Different technologies
and the potential of recovering nutrients using these technologies, and the social,
economic and environmental performance of current and alternative technologies
are discussed.
Chapter 5 explores the status of electronic waste production and approaches for
the recovery of metals from electric and electronic scrap. It is stressed that e-waste is
one of the fast-growing waste streams that contain toxic elements as well as valuable
materials that can be recovered or recycled. Different approaches such as pyrometallurgical, hydrometallurgical and biometallurgical methods for the recovery of metals
from e-waste are discussed in detail. Our analysis shows that no specific method is
ideal in recovering metals with low cost, high recovery rate and low environmental
impact and a combination of recycling methods should be considered to achieve the
most efficient recovery.
Chapter 6 addresses waste plastics and resin production, their compositions and
classifications. It is outlined that the disposal of plastics and resins in landfills or
by open burning is a major source of pollution and creates various environmental,
economic and social impacts. Recycling should be employed as an alternative option
for traditional disposal; however, due to some recycling challenges, conversion of
plastics and resins into liquid products (such as fuels and oils) and activated carbon
are shown to be more preferable methods. Advanced technologies such as pyrolysis, carbonization, steam- and chemical activation for the conversion of plastics
are reviewed extensively and the industrial examples of plastic conversion technologies are introduced. It is suggested that a suitable conversion program is capable of
creating values and jobs and achieving economic growth from the valorization of
waste plastics and resin.
Finally, Chap. 7 presents a detailed overview of advanced technologies for fractionation of lignocellulosic biomass such as crop residues and forestry biomass or
woody biomass into their component polymers (cellulose, hemicellulose and lignin).
Different pre-treatment methods such as physical, chemical, physio-chemical and
8 Summary
Chapter 3 is focused on waste-to-energy conversion as an advanced method for
waste management. Biomass is introduced as the bio-renewable resource for renewable energy production and the two main methods of biological and thermochemical
conversions are highlighted as the main approaches for biomass conversion. The
technologies, processes and industrial applications of each conversion method are
discussed in detail. The technologies covered in this chapter include combustion,
gasification, pyrolysis, liquefaction, digestion and fermentation. The advantages and
disadvantages of each method are discussed and compared in this chapter. The effectiveness of a specific waste-to-energy process is determined by the thermal potential
of the waste, efficiency of the system and the type of produced energy.
The rest of the chapters of the book are focused on resource recovery from various
waste streams. In Chap. 4, nitrogen and phosphorous recovery from wastewater
streams are discussed. The chapter briefly introduces wastewater production and
treatment levels, sludge production, different types of sludge and their characteristics,
as well as treatment methods, while focusing on recovering nitrogen and phosphorous
as the two main nutrients of interest in wastewater and sewage sludge. Current knowledge on recovering these resources from sludge is reviewed. Different technologies
and the potential of recovering nutrients using these technologies, and the social,
economic and environmental performance of current and alternative technologies
are discussed.
Chapter 5 explores the status of electronic waste production and approaches for
the recovery of metals from electric and electronic scrap. It is stressed that e-waste is
one of the fast-growing waste streams that contain toxic elements as well as valuable
materials that can be recovered or recycled. Different approaches such as pyrometallurgical, hydrometallurgical and biometallurgical methods for the recovery of metals
from e-waste are discussed in detail. Our analysis shows that no specific method is
ideal in recovering metals with low cost, high recovery rate and low environmental
impact and a combination of recycling methods should be considered to achieve the
most efficient recovery.
Chapter 6 addresses waste plastics and resin production, their compositions and
classifications. It is outlined that the disposal of plastics and resins in landfills or
by open burning is a major source of pollution and creates various environmental,
economic and social impacts. Recycling should be employed as an alternative option
for traditional disposal; however, due to some recycling challenges, conversion of
plastics and resins into liquid products (such as fuels and oils) and activated carbon
are shown to be more preferable methods. Advanced technologies such as pyrolysis, carbonization, steam- and chemical activation for the conversion of plastics
are reviewed extensively and the industrial examples of plastic conversion technologies are introduced. It is suggested that a suitable conversion program is capable of
creating values and jobs and achieving economic growth from the valorization of
waste plastics and resin.
Finally, Chap. 7 presents a detailed overview of advanced technologies for fractionation of lignocellulosic biomass such as crop residues and forestry biomass or
woody biomass into their component polymers (cellulose, hemicellulose and lignin).
Different pre-treatment methods such as physical, chemical, physio-chemical and