Nav: Home

Think a gasoline-direct injection engine is the green choice? Maybe not

July 13, 2016

Trying to think green when buying a car? Whether your new fuel-efficient engine helps or hurts the warming planet depends on where you live and what you're putting in the tank.

New cars aim to deliver high performance with maximum fuel efficiency, making them easier on both the environment and the wallet. To do this, auto manufacturers are adopting a smaller, more fuel-efficient engine type, called gasoline direct-injection (GDI) -- between model years 2009 to 2015, the percentage of new vehicles sold with GDI engines jumped from five to 46 per cent.

But new research out of the University of Toronto's Faculty of Applied Science & Engineering shows that GDI isn't necessarily the greener choice. Although GDI engines emit lower levels of CO2, they emit more black carbon -- the climate-warming particle commonly known as soot -- and toxic volatile organic compounds, such as benzene and toluene.

"The whole motivation for creating these engines in the first place was fuel efficiency. But what we haven't considered are the other climate-related emissions," says Greg Evans, a professor in the Department of Chemical Engineering & Applied Chemistry and director of the Southern Ontario Centre for Atmospheric Aerosol Research. "If a vehicle emits a small amount of soot, it can completely negate the lower amount of CO2 that it's emitting."

Evans, Dr. Naomi Zimmerman (ChemE PhD 1T5) and Professor Jim Wallace (MIE), director of the Engine Research & Development Lab at the University of Toronto, first studied the chemical composition of emissions from GDI engines. They found that GDI emissions ranked in the 73rd percentile of all vehicles studied for black carbon, and in the 80 to 90th percentile for volatile organic compounds.

They then examined the climate trade-offs between reductions in CO2 emissions and increases in black carbon to determine whether this new engine type confers a net climate benefit. They found that whether GDI engines are the 'greener' choice depends on several factors, including fuel composition, temperature and lifetime of the vehicle.

Their work appeared in two papers in the journal Environmental Science & Technology.

"We found that in some cases, you need up to a 20 per cent improvement in fuel economy in order to offset black carbon emissions," says Zimmerman, lead author on the studies. "Offsetting the black carbon might be realistic in a place like California, where fuel composition is more strictly regulated and seasonal temperatures fluctuate less, but is harder to achieve in Canada."

Evans and Zimmerman also compared conventional gasoline engine types, called port fuel injection or PFI, with GDI engines. They found that replacing an older PFI engine from 2005 with a new GDI engine from 2015 meant an 11 per cent improvement in fuel economy, but swapping a 2010 PFI engine with a 2015 GDI engine only saw a one per cent improvement in fuel economy.

"All the complex interactions show that because of the well intentioned desire to mitigate climate warming, the technology is changing quickly and we are not properly considering all the trade-offs and side effects," says Evans. "As engine designs improve, the balance between all these factors could change again."

University of Toronto Faculty of Applied Science & Engineering

Related Emissions Articles:

Methane emissions from trees
A new study from the University of Delaware is one of the first in the world to show that tree trunks in upland forests actually emit methane rather than store it, representing a new, previously unaccounted source of this powerful greenhouse gas.
Emissions from the edge of the forest
Half of the carbon stored in all of the Earth's vegetation is contained in tropical forests.
An overlooked source of carbon emissions
Nations that pledged to carry out the Paris climate agreement have moved forward to find practical ways to reduce greenhouse gas emissions, including efforts to ban hydrofluorocarbons and set stricter fuel-efficiency standards.
New method for quantifying methane emissions from manure management
The EU Commision requires Denmark to reduce drastically emissions of greenhouse gases from agriculture.
'Watchdog' for greenhouse gas emissions
Mistakes can happen when estimating emissions of greenhouse gases such as carbon dioxide and methane.
A lower limit for future climate emissions
A new study finds that the world can emit even less greenhouse gases than previously estimated in order to limit climate change to less than 2°C.
Study: Second-generation biofuels can reduce emissions
Second-generation biofuel crops like the perennial grasses Miscanthus and switchgrass can efficiently meet emission reduction goals without significantly displacing cropland used for food production, according to a new study.
Large and increasing methane emissions from northern lakes
Climate-sensitive regions in the north are home to most of the world's lakes.
Global CO2 emissions projected to stall in 2015
Global carbon emissions are projected to stall in 2015, according to researchers at the University of East Anglia and the Global Carbon Project.
DXL-2: Studying X-ray emissions in space
On Dec. 4, 2015, NASA will launch the DXL-2 payload at 11:45 p.m.

Related Emissions Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...