Biodiesel 4 times more efficient than diesel
Posted by DavidM in Driving | 10 March 2007
As a relative new user of biodiesel and having been challenged over the real environmental cost of it in relation to biodiesel, I've been looking out for evidence of the overall benefit.
I came across a study carried out by the National Renewable Energy Laboratory for the US Department of Energy and Department of Agriculture in May 1998. It confirmed that the lifecycle environmental cost of biodiesel is far better than that of petroleum-based diesel.
The Biodiesel Lifecycle Inventory Study aimed to give a scientific view of the overall benefit - or otherwise - of biodiesel. The study focused on "those benefits related to biodiesel energy’s balance, its effect on emissions of greenhouse gases, and its effects on the generation of air, water and solid waste pollutants".
And mostly the results are pretty impressive.
For every unit of fossil energy consumed in its life cycle, biodiesel yields 3.2 units of fuel product energy. Petroleum diesel yields only 0.83 units, making biodiesel 4 times more efficient.
Biodiesel reduces net emissions of CO2 by over 78% compared to petroleum diesel.
Biodiesel reduces total particulate matter by 32%, carbon monoxide by 35% and sulfur oxides by 8% compared to diesel.
Tailpipe (exhaust) emissions are vastly improved - small particulates (that stick in the lungs) down 68%, carbon monoxide down 46% and sulfur oxides eliminated completely.
It's not all good though. There are two negative aspects highlighted in the report.
Nitrous oxides increased over 13% and lifecycle emissions of hydrocarbons are 35% higher - though lower at the tailpipe.
This is an important study. Biodiesel looks increasingly attractive economically as well as environmentally but there have been questions about the lifecycle environmental cost being as bad or worse than diesel. This study gives hard evidence to the contrary as well as showing areas for further improvement.
For my personal biodiesel use I think the story is even better. The study was based on biodiesel produced from soyabeans and assumed they were grown explicitly for biodiesel.
The biodiesel I use is recovered at least partially from cooking oil, so the origination energy cost could be discounted. Regardless, I'm pleased that my feelings about biodiesel being a far healthier option than petroleum diesel have been justified.
Hat tip: Alternative energy-renewable energy and Autobloggreen
