Environmental Engineering Reference
In-Depth Information
have been achieved and several high oleic, low linoleic cultivars are now are commercially grown
in Canada (http://www.canola-council.org).
Although canola cultivars were developed to produce high quality edible oil with low to zero
erucic acid (C22:1), development of high erucic acid rapeseed cultivars (known as HEAR) have
progressed in parallel to produce oil for a large number of erucic-acid-based industrial applications
(McVetty et al. 2008).
B.
napus
cultivars with seed oil containing up to 55% erucic acid have been
developed using traditional breeding techniques (McVetty et al. 1999) with 'Reston' being Canada's
first high erucic acid (40-45%), low glucosinolate rapeseed cultivar. It was released in 1982 and
was grown for several years with commercial success (Stefansson and Downey 1995). The current
HEAR cultivars with erucic acid levels of 50-55% or more are being developed for commercial
cultivation by a few breeding organizations around the world [LimaGrain Australia, Danisco Seeds
Denmark, the University of Idaho, the United States, the University of Manitoba Canada), although
germplasm resources having up to 60% erucic acid are available (McVetty and Scarth 2002)].
18.3
enerGy Balance oF
BrASSicA
oIls
18.3.1 E
nErgy
B
alancE
The major use of rapeseed oil for energy, as discussed earlier, is in the production of biodiesel.
However, the feasibility of using vegetable oils, including rapeseed/canola oil for biodiesel production
depends on a positive energy return for the energy used to produce the biodiesel. This is known as the
energy balance. For a biodiesel production system, the energy balance can be determined by studying
the relationship between the output per unit of biodiesel (energy produced) versus the input per unit
of biodiesel (energy consumed) calculated for each unit of product or byproducts (Mootabadi et al.
2008). For this purpose, a life-cycle analysis according to the standards of the International Standard
Organization (ISO 14040-14049) is used to measure the impact of potential factors on the product
life-cycle. The factors considered are the energies required to produce the raw materials, those used
in the production, direct consumption, utilization of waste/byproducts etc. Because rapeseed methyl
ester (RME) is the commonly used biodiesel obtained from rapeseed, life-cycle analysis is generally
done for RME although REE (rapeseed ethyl ester) has also been subjected to life-cycle analysis
(Janulis 2004). In a 2004 study by Janulis, the energy consumption for the production of RME
was classified into three main categories including agriculture, oil pressing and transesterification.
The total energy consumption to produce 1 t of RME was then calculated by adding the energy
consumption in all of the subcategories for agriculture (agromachinery/equipment, fuel and oils,
electricity, seeds/chemicals), oil pressing (electricity, equipment) and transesterification (electricity,
equipment, chemicals). Similarly, the energy content in products (ester, glycerol, straw, oil cake) for
1 t of ester production was added to estimate the total energy produced. Based on these calculations,
the energy balance for rapeseed with a seed yield productivity of 3 t/ha under Lithuanian conditions
came out to be 1.43 for RME and 1.62 for REE.
The energy balance or energy ratios for RME are not static values and could greatly vary
depending not only on the diverse geographic, social, cultural and economic factors but also on
the prevailing conditions within a region. For example, a comparative analysis of two previous
studies (Walker 2004) revealed large differences in energy ratios for RME under good and poor
production/cultural conditions, and also on the basis of outputs included (RME only, RME + rape
meal, RME + rape meal + glycerol, RME + rape meal + glycerol + straw). It was also noted that
glycerol and straw did not have significant impact on energy balance. Other studies have placed
more importance to the value of byproducts and rapeseed straw was found to have a large impact
on energy ratios in some cases (Batchelor 1995; Janulis 2004). Other studies indicated that energy
balance is improved when biofertilizers are used, seed drying (dehydration) is substituted with
chemical conservation and an energy-efficient biotechnological method of oil extraction is used
(Mootabadi et al. 2008). A study conducted in Germany (Rathke and Diepenbrock 2006) revealed
