Page 103 - Refining Biomass Residues for Sustainable Energy and Bioproducts

76 Refining Biomass Residues for Sustainable Energy and Bioproducts

environment. Thus PHAs are better and feasible alternatives to the traditional, non-
biodegradable fossil fuel associated petrochemical analogs, such as polyethylene
and polypropylene.
There have been a number of LCA publications on PHA production using the
LCA software such as SimaPro housing the Ecoinvent databases and impact assess-
ment methods, such as Eco-Indicator 99, TRACI, CML 2, IMPACT2002, and
EDIP97, primarily focusing on the midpoint indicators, such as nonrenewable
energy use (NREU) and greenhouse gas (GHG) emissions (Harding et al., 2007;
Ecoinvent, 2010; Tabone et al., 2010; Tufvesson et al., 2013; Hottle et al., 2013).
Most of the LCA results evaluated were based on the cradle-to-gate assessment as
the maximum number of impact categories could be included in terms of production
and emissions in soil, water, and air. The emphasis on the global warming potential
(GWP) and energy use was more as these were the impact categories where the
emissions were highest but lesser than the petro-polymers (Pietrini et al., 2007; Yu
and Chen, 2008; Kendall, 2012). The other impact categories, such as eutrophica-
tion, human health, land use, or water use, were found to be less than 25%. The
source of heat and power generation is the main cause of emissions that leads to
GWP. Kurdikar et al. (2000) reported that the coal-generated power scenario in the
production of PHA led to the emission of 5.5 kg CO 2 equivalent per kilogram of
PHA. The use of wind power, renewable energy certificates by Vink et al. (2007)
while Kurdikar et al. (2000) used power generated from biomass reported a lower
range of GWP and net negative carbon emissions, respectively. While comparing
polypropylene bags produced in Singapore to PHA bags imported from United
States based on the GWP, acidification and photochemical ozone production as
measures, it was found that the PHA bags had a 69% higher ecological impact than
the PP bags. The probable reason was the usage of electricity from coal and if natu-
ral gas sourced as electricity was to be used, the impacts of the PHA bags could be
reduced to 20% (Khoo et al., 2010). Even though bio-based products exhibited
decreased GHG emissions, increase of water quality degradation was experienced
(Miller et al., 2007). Studies have observed that the production of PHA from waste
or starch-based polymers showed a lower NREU impact compared to petrochemical
plastics (Kendall, 2012; Yates and Barlow, 2013). Harding et al. (2007) reported
lower acidification potential (AP), eutrophication potential (EP), ozone depletion,
human health toxicity, and ecotoxicity, while Kendall (2012) and Kim and Dale
(2005) found that PHB showed higher AP and EP in comparison to a number of
petrochemical polymers.
LCA studies on EPS production have been very limited or in other words have
not been studied yet. A sustainability assessments study was conducted on the
recovery of resources, such as microbial-synthesized alginate, PHA, cellulose, bio-
gas from waste water that selected the most competitive sustainability-enhancing
technologies, that is, LCA having themes under resources, environmental quality,
and human health (Zijp et al., 2017). PHA production resulted in a slight increase
in mineral and fossil depletion but decrease land use and water depletion; cellulose
recovery resulted in extra fossil depletion while alginate production quantified ben-
eficial impact for all mineral and fossil depletion, land use, and water depletion.