I recently attended a tour of the Z Energy’s Biodiesel Plant in New Zealand. Z’s biodiesel will be available to customers as a B5 blend (up to 5% biodiesel blended with ordinary diesel) and is already being used by commercial customers as a B20 blend.
I attended the tour with a well meaning friend who was genuinely interested, but even after the Q&A session with the plant manager and marketing manager he couldn’t reconcile their explanation of how using waste-grade beef tallow meant the carbon emissions were somehow less when burned as opposed to petroleum diesel from the ground. He’s asked The Energy Project to Explain.
When used as a vehicle fuel, biodiesel offers some tailpipe and considerable greenhouse gas (GHG) emissions benefits over conventional gasoline and diesel, and can be explained using life cycle analysis.
Life cycle analysis is a technique used to assess the environmental impacts of all stages of a product’s life, including raw material extraction, processing, manufacturing, distribution, use, and disposal or recycling. When comparing fuels, a life cycle analysis may focus on particular portions of a fuel’s life cycle, such as from extraction-to-use or well-to-wheels, to determine the merits or problems associated with each fuel.
Life cycle analysis completed by TUG Institute for Resource Efficient and Sustainable Systems found that greenhouse gas emissions for 100% biodiesel (B100) are 74% lower than those from petroleum diesel.
The scope of the LCA study analysed the provision of the product biodiesel from tallow and biodiesel from used vegetable oil from raw material extraction to fuel combustion. The production of energy, raw materials and auxiliary materials is included as is the waste disposal and the treatment of liquid and gaseous emissions during all steps of the life cycle. It can be neatly summarised in the tree structure below:
Tree structure of the Life Cycle Impact Assessment
The overall absolute impacts as well as the relative contributions of the LCA phases of biodiesel from tallow are highly sensitive to the allocation in the cattle breeding and the slaughtering process. A large part of the cattle-breeding footprint can be attributed to fodder-production and emission of ammonia and slaughtering process.
However, a key part of Z Energy’s model is that they are using exclusively waste-grade tallow in the production of their B5. This tallow is not fit for human consumption and would otherwise be exported for the production of soap and candles.
This model recognises that the slaughtering process is above all carried out to produce meat. Without the returns from meat sale the slaughtering process and the upstream processes related to meat, production would not be profitable. Without meat sales there would be no upstream processes and no slaughtering. This model allows Z Energy to effectively discount the footprints from breeding and slaughtering in their LCA reducing it by approximately 82% than the LCA for its non-waste grade counterpart (where breeding and slaughtering are carried out not for meat production, but for the production of biofuel.
Contrast this with the intensive process involved with conventional petroleum diesel LCA:
Table Credit: Banergee et al., (2016) http://www.researchgate.net
Where exploration forms a prominent part of the LCA. Also the environmental impacts taken into consideration with petroleum diesel include: organic respiratory effects, inorganic respiratory effects, fossil fuels, acidification – eutrophication, greenhouse effect, ecotoxicity and carginogenic effects. These impacts are not seen with biodiesel. However, the use of biodiesel as transportation fuel increases emissions of PM10, nitrous oxide, nitrogen oxides and nutrients such as nitrogen and phosphorous; the latter are the main agents for eutrophication.
From an environmental standpoint, the use of biodiesel is superior as it results in significant reductions of GHG emissions in comparison to gasoline and diesel. It also has lower well-to-wheel emissions of methane.
