لخّصلي

The growth of energy demand, particularly, in developing
countries has led to the huge requirement of fossil fuels.
Going with present energy scenario, one has to switch to
renewable energy resources for the sustainable development.
Production of fuels from bio-based feedstock is one such
process which can deliver a sustainable solution in current
energy scenario. Use of algae, jatropha, canola, corn, etc. for
the production of biodiesel has become popular. But, the
production of algae does not require land, large quantities of
water and too much labour as required by the other feedstock.
Algae are autotrophs that utilize CO2 and sunlight through
photosynthesis to produce biodiesel and other bio fuels [1].
Various researchers have carried out the biodiesel production
using algae in laboratory designed photo bioreactors. The
biodiesel production follows the following steps: cultivation
of microalgae, flocculation, centrifugation, extraction, and
transesterification [2]. Algae based biodiesel production is an
area of current research where many studies are carried out
with a focus on harvesting of algae and its processing
technologies. Clarens et al [3] have carried out the life cycle
comparative studies of bio-energy feed stocks from algae. The
work also suggests that the demand of CO2 and fertilizers can
be met by using flue gas as a source of carbon dioxide and
wastewater as a source for nutrients. Stephenson et al [4]
carried out the life cycle assessment of algal biodiesel
production using Chlorella Vulgaris. 1 ton of biodiesel was
chosen as the functional unit to estimate the emissions. The
fossil energy requirement and Global Warming Potential
© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the scientifi c committee of the 25th CIRP Life Cycle Engineering (LCE) Conference
Smita Raghuvanshi et al. / Procedia CIRP 69 ( 2018 ) 568 – 572 569
(GWP) from Chlorella Vulgaris grown in raceways are nearly
85% and 78% which are lower than the fossil derived diesel.
A combinatorial life cycle assessment study was carried
out by Brentner et al. [5] which follows a cradle to grave
approach. The system boundary includes cultivation,
harvesting, lipid extraction, conversion, and disposal and
excludes labor, transport infrastructure, capital machinery, or
combustion of biodiesel. The results show cumulative energy
demand, greenhouse gas (GHG) emissions, water use,
eutrophication, direct land requirements, etc. Ferreira et al [6]
have carried out the detailed life cycle analysis for energy
consumption and CO2 emission from Nannochloropsis
species using a bio refinery method and cradle to grave
approach. This assessment has covered cultivation,
harvesting, dewatering, milling, lipid and pigment extraction
and also has shown leftover biomass to H2 production.
Handler et al [7] have studied the life cycle assessment of
algal based bio fuels and chose 1 MJ of fuel produced as a
functional unit. Results included GHG emissions and fossil
energy demand for each scenario. The results indicate that
GHG emissions are higher for fossil fuels and gave insights
for other wastewater sources to be used for algae growth.
Most of the literature for the production of biodiesel from
algae has used pure algal strain and pure CO2 for the
cultivation of algae and LCA boundaries. However, with
growing need of sustainable processes, few studies have
grown algae in wastewater as source of nutrients and have
used CO2 from flue gases for the development of algae
culture. The major resources used for the production of algae
are water and nutrients. Fortunately, wastewater also contains
nutrients. Therefore, the use of wastewater for biodiesel
production is highly sustainable. This work discusses the life
cycle assessment studies for biodiesel production using algae
grown in fresh water and wastewater in order to show the
sustainability of scaled up processes.
2. Life cycle inventory analysis
2.1. Goal and scope of present study
The goal of this study is to examine the feasibility of
production of biodiesel from microalgae using wastewater and
fresh water. The cultivation of microalgae are completely
supplied by using wastewater released from the domestic and
office use. The algal strain selected was Chlorella vulgaris
which has a growth rate of 15 g/m2 per day having
productivity of 25%. The composition of wastewater are:
COD (Chemical Oxygen Demand) of 0.1556 kg/m3
, BOD
(Biological Oxygen Demand) of 0.1036 and TOC (Total
Organic Carbon) of 0.0673 kg/m3
. Cultivation of microalgae
was in open ponds having an area of 0.5 hectare. The study
has used a cradle to gate approach for the impact assessment.