Finally, we have answers to some of the more vexing questions in sustainable personal transport (via what green car).
How's that? A respected consultancy in Britain has undertaken the first 'life cycle' assessment of our current choices among vehicles.
What's especially instructive about this research is that it considers the environmental impacts from the fuel cycle (primary production, transportation, refining, and vehicle operation), and also assesses the impacts from the vehicle cycle (materials production, vehicle manufacture and disposal).
This is fascinating stuff, given our urgent need to look beyond mpg for a reliable measure of transport's footprint.
This report is worth slogging through, because you'll learn:
- the material composition of different vehicles and the eco-impacts of these material choices
- the energy value of alternative fuels and the true costs of producing them
- cost-benefit measures for alternative propulsion technologies
You'll also learn why a hybrid SUV is worse for the environment than a standard SUV, and why the newfangled Toyota Prius is only slightly less damaging than an off-the-shelf Honda Civic.
Wow! This opens up whole new sets of questions, no?
The bottom line is this: big cuts in our transport emissions (of a magnitude that is commensurate with our urgent need to reduce) will take radical steps.
For example, it's not enough to drive an electric car. You must also recharge your batteries from renewable sources.
If you do this, your transport footprint will shrink by 80%...And that's with no reduction in miles traveled.
Go figure. (Oh, and mebbe the best short-term bet is simply to reduce our miles...)
The analysis covers five types of fuel, including petrol, diesel, bioethanol, biodiesel, natural gas, and liquefied petroleum gas, as well as two types of electric vehicles, including battery electric and hybrid electric.
Says Ecolane Transport Consultancy:
"This study, Life Cycle Assessment of Vehicle Fuels and Technologies, focuses exclusively on quantifying the extent and impacts of life cycle air-borne emissions arising from the fuel and vehicle cycles."
Research results are presented for each of five car classes, including city cars, small cars, small family cars, large family cars or MPVs, and SUVs.
One of the key findings of the LCA study is that vehicle size is as important a determinant of emissions impacts as fuel or technology type.
Moving down from a large to a medium sized passenger car equates to a reduction in the total life cycle environmental impact of around 12%-16%.
Looking only at size, the environmental impact of the smallest vehicles is 60% less than SUVs.
From a life cycle perspective, it's interesting to note that only 80% of emissions come from driving. The other 20% is generated in the production of the vehicle and the fuel.
In other words, 1/5 of your emissions have already occurred before you purchase the car or start the engine.
It's also noteworthy that alternative fuels often involve greater fuel production emissions, which must be offset against mileage savings. And, for the first time, we've got some reliable benchmark measures of how these offsets might work.
It's fascinating to note that, by this measure, diesel and petrol are essentially equivalent, while biodiesel reduces overall impacts by 13% versus the petrol standard.
Note as well that two other choices with equivalent benefits are: bioethanol or petrol-hybrids, both of which can cut 23% versus petrol.
The biggest benefits can come from electric vehicles whose batteries are charged from renewable sources. This can cut 80% of the environmental impact versus petrol.
Incidentally, electric vehicles charged from non-renewable sources are roughly equivalent to hybrids.
One reason hybrids score lower than one might expect based solely on mileage is the extra impacts associated with the materials and fuels used.
On average, for example, the materials in hybrids have 30% more environmental impact and their fuels have 40% more impact than conventional vehicles.
Look it up yourself! The eco-impact scoring includes all the measures cited above; lower is better, with 100 being about as bad as they come.
Prius gets one of the best eco-impact score (35; lower is better), which is the same as BMW's SUV (35), and only slightly better than Honda's Civic hybrid (37), which is equal to the Ford Focus (37 with flex-fuel), which is only slightly better than the regular Civic (38), which is only slightly better than the Hyundai Accent (39).
Notice that these scores do exhibit a strong correlation with mpg (with an adjusted R square of .88). Still, other factors such as materials and technology have sometimes counterintuitive results.
For example, the Lexus hybrid SUV actually scores worse (at 61) than other SUVs (like Dodge Caliber at 47). Wot's the clue?
Ecolane undertook this research as part of the Clear Zones campaign on behalf of the London Borough of Camden.
For the first time, this new research can be used to compare the life cycle environmental performance of cleaner vehicles with each other and against conventional vehicle fuels/technologies to inform future transport policy developments.
'K den, let's get'r done!