107
5.1 Background and Introduction
5.1.1 Plastic Production, Disposal, and Sustainability
In our daily life, we are surrounded by plastic materials. Whether it is plastic bags
for food packaging, furniture and appliances, or disposable containers, they have
become an indispensable material in our day-to-day activities due to their light
weight and durability. While plastics have dramatically improved and simplified our
lives, the use of plastics for packaging and other purposes has increased the issue of
solid waste disposal (Salehizadeh and van Loosdrecht 2004). Plastic use and polymer production have grown steadily for the past 50 years increasing from 15 million
tons in 1964 to 311 million tons in 2014 (World Economic Forum 2016).
These vast quantities of polymer products require disposal or recycling at the end
of their life cycle. It was estimated in the 1990s that plastics were accumulating at a
rate of 25 million tons/year (Salehizadeh and van Loosdrecht 2004). This rate is
expecting to increase until 2020 (Castilho et al. 2009). While the majority of disposed plastic products are recyclable, around 22–43% of polymers disposed annually end up in landfills, which have low degradation rates and can potentially lead to
groundwater pollution by leaching out toxic additives. Incineration is also used;
however, it is an expensive option associated with harmful air emissions (Castilho
et al. 2009). Only 9% of plastics are recycled properly, while the rest are not recovered. Moreover, when these polymer wastes enter the environment, they may take
up to 2000 years to break down (Dietrich et al. 2017). This results in an estimated
eight million metric tons/year of accumulation (Jambeck et al. 2015), with an estimate of 100 million tons in the Pacific Ocean alone (Marks and Howden 2008). As
a consequence, it is estimated that more than a million aquatic animals are killed
yearly by choking on or ingesting plastic debris (Rodriguez-Valera 1991). In addition to disposal issues, the vast majority of polymers are currently produced from
petroleum feedstocks, consuming currently around 6% of total petroleum use and
estimated to rise 20% by 2050 (World Economic Forum 2016). The conversion
processes typically involve high heat and pressure resulting in significant energy
consumption and carbon dioxide emissions (National Research Council 1994). In
light of growing concern over global warming, international agreements to mitigate
greenhouse gas emissions and efforts to slow fossil reserve depletion, there is a
developing interest from industry and consumers toward alternatives.
Bioplastics have been suggested as an environmentally friendly alternative to
petrochemical plastics. Bioplastics are polymers that are either (1) biobased, meaning derived from renewable biomass resources such as agricultural feedstocks, (2)
biodegradable, meaning bioplastics that degrade naturally in the environment, or (3)
biobased-biodegradable, which meet both criteria and are the most desirable
(Fig. 5.1). However, with respect to agricultural feedstocks, concerns still exist,
similar to biofuel crop production, over potential competition with food crops for
land and water resources (Detzel et al. 2013). Therefore, use of waste residues as
feedstock, where compatible with the bioplastic production process, is a more
5 Integration of Polyhydroxyalkanoates Production with Industrial Wastewater…
5.1 Background and Introduction
5.1.1 Plastic Production, Disposal, and Sustainability
In our daily life, we are surrounded by plastic materials. Whether it is plastic bags
for food packaging, furniture and appliances, or disposable containers, they have
become an indispensable material in our day-to-day activities due to their light
weight and durability. While plastics have dramatically improved and simplified our
lives, the use of plastics for packaging and other purposes has increased the issue of
solid waste disposal (Salehizadeh and van Loosdrecht 2004). Plastic use and polymer production have grown steadily for the past 50 years increasing from 15 million
tons in 1964 to 311 million tons in 2014 (World Economic Forum 2016).
These vast quantities of polymer products require disposal or recycling at the end
of their life cycle. It was estimated in the 1990s that plastics were accumulating at a
rate of 25 million tons/year (Salehizadeh and van Loosdrecht 2004). This rate is
expecting to increase until 2020 (Castilho et al. 2009). While the majority of disposed plastic products are recyclable, around 22–43% of polymers disposed annually end up in landfills, which have low degradation rates and can potentially lead to
groundwater pollution by leaching out toxic additives. Incineration is also used;
however, it is an expensive option associated with harmful air emissions (Castilho
et al. 2009). Only 9% of plastics are recycled properly, while the rest are not recovered. Moreover, when these polymer wastes enter the environment, they may take
up to 2000 years to break down (Dietrich et al. 2017). This results in an estimated
eight million metric tons/year of accumulation (Jambeck et al. 2015), with an estimate of 100 million tons in the Pacific Ocean alone (Marks and Howden 2008). As
a consequence, it is estimated that more than a million aquatic animals are killed
yearly by choking on or ingesting plastic debris (Rodriguez-Valera 1991). In addition to disposal issues, the vast majority of polymers are currently produced from
petroleum feedstocks, consuming currently around 6% of total petroleum use and
estimated to rise 20% by 2050 (World Economic Forum 2016). The conversion
processes typically involve high heat and pressure resulting in significant energy
consumption and carbon dioxide emissions (National Research Council 1994). In
light of growing concern over global warming, international agreements to mitigate
greenhouse gas emissions and efforts to slow fossil reserve depletion, there is a
developing interest from industry and consumers toward alternatives.
Bioplastics have been suggested as an environmentally friendly alternative to
petrochemical plastics. Bioplastics are polymers that are either (1) biobased, meaning derived from renewable biomass resources such as agricultural feedstocks, (2)
biodegradable, meaning bioplastics that degrade naturally in the environment, or (3)
biobased-biodegradable, which meet both criteria and are the most desirable
(Fig. 5.1). However, with respect to agricultural feedstocks, concerns still exist,
similar to biofuel crop production, over potential competition with food crops for
land and water resources (Detzel et al. 2013). Therefore, use of waste residues as
feedstock, where compatible with the bioplastic production process, is a more
5 Integration of Polyhydroxyalkanoates Production with Industrial Wastewater…