Ind. Eng. Chem. Res. 2010, 49, 11785–11796
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Biodiesel Production from Canola in Western Australia: Energy and Carbon Footprints and Land, Water, and Labour Requirements Ferry Rustandi and Hongwei Wu* Curtin Centre for AdVanced Energy Science and Engineering, Department of Chemical Engineering, Curtin UniVersity of Technology, GPO Box U1987, Perth WA 6845, Australia
This study evaluates the energy and carbon footprints and land, water, and labor requirements of biodiesel production from canola in Western Australia (WA). The results show that canola-based biodiesel leads to limited energy profit and CO2 equivalent (CO2-e) emissions savings. Even when all byproduct are utilized, a relatively low output/input energy ratio of 1.72 and a CO2-e emissions savings of only 0.52 kg of CO2-e/L of biodiesel are obtained under the WA conditions considered in this study. A land requirement of 1.66 × 10-3 ha/L of biodiesel means that canola-based biodiesel seems to also be limited to 1 in Table 1), with a highest R value of 1.72 (R6) evaluated in this study when straw, canola meal, and glycerol are utilized as indicated by Table S8 in the
Supporting Information. Therefore, the energy profits of biodiesel production from canola in WA are critically dependent on the amount of byproduct that can actually be utilized. Failure to utilize canola meal and glycerol would decrease the energy profit, and the excess byproducts would likely be regarded as waste, whose disposal would incur energy costs that increase the energy footprint and decrease the energy profit. It is known that, for an alternative liquid transport fuel to make a realistic contribution to future energy security, a scale of production that can contribute 10-20% or more of the total liquid transport fuel consumption would be necessary.32 To replace 10-20% of the total diesel fuel consumption in the WA transport sector in a typical year, 4.88-9.76 PJ of biodiesel would have to be produced from canola annually.3 At this scale, the canola oil extraction process would generate approximately 0.19-0.38 million tonnes of canola meal annually. This amount of canola meal in WA alone would supply approximately
Ind. Eng. Chem. Res., Vol. 49, No. 22, 2010 Table 2. Carbon Footprint of Biodiesel Production from Canola in WA and CO2-e Emissions Savings Obtained by Replacing Diesel Fuel with Canola-Based Biodiesel carbon footprint CO2-e emissions savings (kg of CO2-e/L (kg of CO2-e/L of biodiesel) of biodiesel) without byproduct utilization with straw utilization with meal utilization with meal and glycerol utilization with straw and meal utilization with utilization of straw, meal, and glycerol
3.72 3.21 3.15 2.98 2.63 2.47
-0.74 -0.22 -0.16 0.0046 0.35 0.52
18-44% of the total Australian protein meal consumption from all oilseed crops in a typical year.33 Similarly, 13.5-27 million kg of glycerol would be generated by the transesterification process, and it has been reported34 that, although some major Australian biodiesel producers utilize glycerol, most manufacturers simply burn the byproduct. It is also known that only limited amounts of straw can be utilized,7,35 as the harvesting of residues from agricultural land facilitates soil erosion, which leads to further energy costs associated with replacement of increased runoff water and of essential soil nutrients that are lost as a result of erosion. Consequently, only approximately 10% of the total straw produced is considered for utilization in this study (Table S8 in the Supporting Information). Therefore, the contribution of canola-based biodiesel to future energy security in the WA transport sector is limited and strongly dependent on the utilization of byproducts. The canola-based biodiesel production process consumes substantial nonrenewable fuels and leads to only limited energy profit. 3.2. Carbon Footprint. The carbon footprint of biodiesel production from canola in WA and the CO2-e emissions savings obtained from replacing diesel fuel with canola-based biodiesel are reported in Table 2. The CO2-e emissions from each stage of the production process are shown in Figure 5 without byproduct utilization to identify the major contributors of CO2-e emissions. In addition to being the most energy-intensive stage, canola growing also dominates the overall CO2-e emissions with the CO2-e emissions from managed cropland constituting the single largest CO2-e emissions contribution from the whole production process. The CO2-e emissions associated with production of fertilizers are another major contributor, followed by moderate contributions from CO2-e emissions associated with production of pesticides, diesel fuel consumption (mainly during field machinery operations), and process heat requirements (mainly during the oil extraction process). Other CO2-e emissions make only minor contributions. When no byproducts are utilized or when only straw or canola meal is utilized (with or without glycerol), there is no or only marginal CO2-e emissions savings. This suggests that canolabased biodiesel in fact leads to little reduction in GHG emissions when it is used to substitute mineral diesel in the WA transport sector. Only when at least both straw and canola meal are utilized, the carbon footprint of canola-based biodiesel can provide some opportunity to reduce CO2-e emissions from the production and use of conventional diesel on an equivalentenergy-content basis. The highest CO2-e emissions savings is 0.52 kg of CO2-e/L of biodiesel when all of the byproducts, including straw, canola meal, and glycerol, are utilized, as indicated in Table S8 in the Supporting Information. However, as discussed in the previous section, because of the large biodiesel production scale that is required and the soil erosion facilitated by harvesting residues from agricultural areas, it will be difficult to achieve a high percentage utilization of the byproducts from the canola-based biodiesel production process
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in WA. Therefore, the role of canola-based biodiesel in reducing GHG emissions from the WA transport sector is also limited and strongly dependent on the utilization of byproducts. 3.3. Land, Water, and Labor Requirements. The land, water, and labor requirements per liter of biodiesel produced from canola in WA were assessed, and the results are presented in Table 3. The land, water, and labor requirements of canolabiodiesel production as a function of the target percentage of total mineral diesel fuel consumption in the WA transport sector in a typical year were calculated, and the results are listed in Table 4. The results are also compared to the actual land and water availability and labor productivity in supplying diesel fuel to the transport sector in WA in a typical year (Table S12 in the Supporting Information). The results in Table 4 clearly suggest that canola-based biodiesel can only play a minor role in the future energy security and GHG emissions reduction in the WA transport sector. For example, to replace 10% of the total diesel fuel consumption in the WA transport sector in a typical year, approximately 60% of the cropland area used for growing oilseeds (for food production) in WA in a typical year must be dedicated to canola growing for biodiesel production. Therefore, most of annual canola harvest would be used for biodiesel production, and more arable land would need to be provided for growing canola for other purposes, such as production of edible oil, causing serious competition with food production using arable land. In fact, even a 2% replacement requires 12% of the current cropland area for growing oilseeds (for food production) in WA in a typical year to be dedicated to canola growing for biodiesel production. Therefore, the land requirement is expected to be the major constraint on the realization of canola-based biodiesel’s potential as a sustainable transport fuel to replace diesel fuel in the WA transport sector. The results in Table 4 indicate that, to minimize its competition with food production, canola-based biodiesel should only replace less than 2% of the total annual diesel fuel consumption in WA. Because of the rain-fed cropping system in growing canola in WA,22 the water requirement of the production process mainly derives from the canola processing stages (Tables S2 and S3 in the Supporting Information). As a result, only a very small fraction of the total water resource availability in WA in a typical year, equivalent to less than 1% of the total water consumption in the WA agricultural sector, is required to be dedicated to the production process. Therefore, the water requirement seems to be insignificant, although it might become a constraining factor during periods of drought. This is because the amount of total annual water resource strongly depends on the amount of rainfall and the variability of Australian rainfall from year to year and season to season.2 In terms of labor requirement, 9.15 × 10-3 h of labor is required per liter of canola-based biodiesel (Table 3). This is the total number of direct labor hours required in producing biodiesel, which includes the labor hours during canola growing, oil extraction, transesterification, and transport activities (Tables S1-S4 in the Supporting Information). This labor requirement is compared to 1.52 × 10-2 h of direct labor required per liter of diesel fuel supplied to the WA transport sector (Table S12 in the Supporting Information), which includes the labor hours during oil mining/extraction, refinery, and diesel distribution. Within the limited fraction of diesel fuel that might replaced by biodiesel without causing significant competition for arable land, the fact that fewer labor hour are required in producing biodiesel than diesel (higher throughput for biodiesel than for diesel fuel, as shown in Table 4) means that there would be
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Ind. Eng. Chem. Res., Vol. 49, No. 22, 2010
Figure 5. CO2-e emissions from each stage of biodiesel production from canola in WA without byproduct utilization (bd ) biodiesel).
Table 3. Land, Water, and Labor Requirements of Biodiesel Production from Canola in WA requirement land water labor
units
value
10 ha/L of biodiesel L of water/L of biodiesel 10-3 labor h/L of biodiesel
1.66a 2.44b 9.15c
-3
a Calculated from canola, canola oil, and biodiesel yields (Tables S1-S3 in the Supporting Information). b Calculated from canola processing water requirements (Tables S2 and S3 in the Supporting Information), assuming 80% water supply efficiency.7 c Calculated from labor hour requirements during canola growing and processing and during canola, canola oil, and biodiesel transport (Tables S1-S4 in the Supporting Information).
enough biodiesel to support transport activities that are usually supported by diesel fuel in the WA transport sector. 3.4. Net Energy Analysis. The limited energy profit obtained in the biodiesel production process means that the contribution of canola-based biodiesel to future energy security in the WA transport sector is still constrained by the availability of nonrenewable fuels to supply energy for the production process. As already pointed out, the net energy approach is used to make the process not dependent on nonrenewable fuels by investing some of the produced biodiesel back into the process, leaving only the net biodiesel available as replacement for diesel fuel, as shown in Figure 3. The ratio of net-to-gross output of biodiesel (F*/F1 in Figure 3) associated with the maximum
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Table 4. Land, Water, and Labor Requirements of Canola-Based Biodiesel Production to Replace Diesel Fuel Consumption in the WA Transport Sector in a Typical Year percentage of annual diesel fuel consumption replaced
a
biodiesel production requirement (GL/year) land requirement 106 ha/yearb as percentage of total cropland area in WAc as percentage of total area sown for oilseeds in WAd water requirement GL/yeare as percentage of total water resource in WAf as percentage of total water use in WAg as percentage of water use in WA agricultural sectorh labor requirement (106 labor h/year)i biodiesel throughput (GJ/h)j diesel throughput (GJ/h)k
1
2
10
20
50
100
0.01
0.03
0.15
0.30
0.74
1.49
0.02 0.20 6.01
0.05 0.41 12.03
0.25 2.04 60.14
0.49 4.08 120.27
1.23 10.19 300.68
2.47 20.39 601.37
0.04
