Life cycle assessment of environmental outcomes and greenhouse gas emissions from biofuels production in Western Australia

Sep 2008

This study examines the full life-cycle of greenhouse gas emissions from the production of ethanol and biodiesel by undertaking a life-cycle analysis (LCA) to assess the greenhouse gas emissions and other environmental outcomes as a result of Western Australian biofuels use. The LCA compares the Western Australian situation with, and without, biofuel production; specifically biofuel from two plants – 45 ML of biofuel from Picton ARF biodiesel facility and 160 ML of ethanol from Primary Energy proposed biorefinery.
The greenhouse benefits of biofuel are normally derived from the substitution of fossil based carbon emissions (which are the result of the combustion of fossil fuels), with biogenic carbon dioxide emissions (which are the results of combusting fuels that have only recently absorbed the carbon from the atmosphere during the cropping cycle). In the Western Australian case there are a number of other significant greenhouse contributors and savings. The most dominant of these is the electricity production from the Primary Energy biorefinery. Because Western Australian electricity is largely based on coal combustion, the greenhouse benefits of substituting this electricity with electricity from the bio-refining are significant. In fact, the greenhouse gas savings from electricity production (281 Gg)1 are more than the savings generated from ethanol production (205 Gg) .To some extent the biorefinery could be considered to be an electricity plant that produces ethanol and fertilisers as co-products.
Without the biodigester part of the biorefinery the ethanol production and utilisation are still beneficial from a greenhouse gas perspective though the savings per year are more than halved from 486 Gg to 220 Gg for the 160ML of production. In terms of fuel security the ethanol production has relatively low crude oil inputs over the lifecycle with 20 more times energy being produced than crude oil energy utilised through the life cycle.
These benefits come at the cost of land use with very little land utilisation in the crude oil to petrol supply chain compared with the land needed for wheat production. The overall sustainability of this use is beyond the scope of this LCA, as is the sustainability of the continued crude oil utilisation.
There is also a net greenhouse benefit from biodiesel production (from tallow) and its subsequent use as a biodiesel blend. This benefit is entirely from tailpipe emission savings due to biogenic carbon dioxide emissions replacing fossil derived carbon dioxide emissions. The production stage of biodiesel is significantly higher than the equivalent volume of diesel production but this is more than offset by the tailpipe emission savings.
Co-products from biodiesel production, namely glycerol and potassium sulfate make little impact on the final environmental profile of biodiesel. The benefit from the biodiesel per year is 44 Gg of greenhouse gases for the 45 ML of production. The combined reduction from biodiesel and ethanol implementation is 530 Gg per year, which represents 0.76% of the 2006 greenhouse gas emissions in WA and 6% of WA transport related emission for the same year.
The biodiesel and ethanol facilities both reduce the total demand for fossil fuels and especially the demand for crude oil. For each unit of fossil energy (oil and natural gas) into the biodiesel life cycle, 3.3 units of usable energy are produced. For ethanol this ratio is 9.7. If one focuses on fuel security by examining only the crude oil and liquid transport fuels (rather than the overall fossil) as the inputs, then each unit of crude oil input produces 16.3 and 15.0 units of usable liquid fuels for the biodiesel and ethanol process respectively. When energy offsets during the production of ethanol are included then the ratio can increase to 20.3. In relation to urban air pollutants, the benefits of biodiesel blends in reducing particulate matter are well established but are also highly variable, as is the increase in emissions of oxides of nitrogen.
For ethanol only an E10 blend was assessed in this study, but for biodiesel blends from 5% to 100% were assessed; the environmental impacts per unit of biodiesel utilised did not vary. This suggests that the most convenient and practical blend should be based on vehicle requirements.

By: T. Grant, T. Beer, P. K. Campbell, D.Batten

 
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