Nav: Home

Calculating the CO2 emissions of biofuels is not enough

January 29, 2018

"In my study, I wanted to show that calculating the greenhouse gas emissions of biofuels tells just half of the story. What we really need to do is quantify the emissions of each product coming out of biorefineries," says Edgard Gnansounou, professor at EPFL and head of the school's Bioenergy and Energy Planning Research Group. To that end, Gnansounou has developed a sophisticated computer model described in an article appearing in Bioresource Technology.

Biofuels and other biomass-derived products have become viable options for replacing fossil fuels. But they have to meet certain environmental standards if they are to genuinely help cut carbon emissions. Under a new EU directive, bioethanol-based fuels - which are made by fermenting biomass - must save 70% greenhouse gas emissions compared to their fossil-fuel counterparts starting in 2021. In Switzerland, the government passed a law requiring that from 1 August 2016, biofuels must cut greenhouse gas emissions by at least 40% relative to fossil-fuel equivalents. However, calculating the total greenhouse gas emissions of biofuels is no mean feat. The entire processing chain - not just the production of the biofuel itself - must be taken into account. For sugar cane, that would include emissions from growing and harvesting the plant, transporting it to a biorefinery, turning it into biofuel, and producing the other compounds and animals feed supplements that are generally made as coproducts. The hitch is that until now, no computer model existed for analyzing the entire life cycle of each product and coming up with a single emissions figure subject to environmental requirements.

One major challenge is the many different variables involved in calculating the emissions of biofuels and their various coproducts. But after five years of research, Gnansounou has come up with a model that incorporates all the various data. "I tackled the problem of allocating greenhouse gas emissions among the different coproducts by specifying an environmental requirement for each one. That lets plant engineers compare those emissions with their fossil-fuel equivalents and set up the right incentives to make their biorefineries economically viable."

Gnansounou's model is intended for second-generation biorefineries, which are still relatively new - only five currently exist around the world. The advantage of these biorefineries is that instead of processing crops that are also used as food, they use debris from farming (like wheat straw) and foresting. Wheat straw is the crop that Gnansounou looked at specifically, taking into account the wheat ears, which are used for food, and the stems, which are used by biorefineries to produce bioethanol for fuel, biogas for heating and electricity and phenol for the chemical industry. He also factored emissions from the fertilizer and farming machines used to grow and harvest the wheat, and whether the field had previously been used for other crops. Once he calculated a total greenhouse gas emissions figure, he used his model to divide the total up among the various coproducts.

With his research, Gnansounou hopes to bring a scientific perspective to the political and economic debate on biofuels. "Second-generation biorefineries should replace some oil refineries, but engineers still don't have a clear method for calculating emissions across a biofuel's life cycle," he says. "What's more, biorefineries have trouble competing with low oil prices" - since biofuels are two to three times more expensive than fossil fuels. He concludes: "Policymakers still haven't fully grasped the emissions challenge, which is why it's a good area for research." Gnansounou believes that the renewable energy industry is too focused on the greenhouse gas emissions of biofuels alone, whereas it should be looking more closely at the emissions of each coproduct from biorefineries, subject to climate policy constraints. That would also give consumers more information about the sustainability of biomass-derived products. Gnansounou plans to continue his research on other types of crops and publish his findings in a second article.
-end-


Ecole Polytechnique Fédérale de Lausanne

Related Biofuels Articles:

Barriers and opportunities in renewable biofuels production
Researchers at Chalmers University of Technology, Sweden, have identified two main challenges for renewable biofuel production from cheap sources.
How biofuels from plant fibers could combat global warming
A study from Colorado State University finds new promise for biofuels produced from switchgrass, a non-edible native grass that grows in many parts of North America.
Calculating the CO2 emissions of biofuels is not enough
A new EU regulation aims to shrink the environmental footprint of biofuels starting in 2021.
Algae cultivation technique could advance biofuels
Washington State University researchers have developed a way to grow algae more efficiently -- in days instead of weeks -- and make the algae more viable for several industries, including biofuels.
Cutting the cost of ethanol, other biofuels and gasoline
Biofuels like the ethanol in US gasoline could get cheaper thanks to experts at Rutgers University-New Brunswick and Michigan State University.
Cellulosic biofuels can benefit the environment if managed correctly
Could cellulosic biofuels -- or liquid energy derived from grasses and wood -- become a green fuel of the future, providing an environmentally sustainable way of meeting energy needs?
Making oil from algae -- towards more efficient biofuels
The mechanism behind oil synthesis within microalgae cells has been revealed by a Japanese research team.
WSU study finds people willing to pay more for new biofuels
When it comes to second generation biofuels, Washington State University research shows that consumers are willing to pay a premium of approximately 11 percent over conventional fuel.
'Super yeast' has the power to improve economics of biofuels
Scientists at the University of Wisconsin-Madison and the Great Lakes Bioenergy Research Center have found a way to nearly double the efficiency with which a commonly used industrial yeast strain converts plant sugars to biofuel.
Biofuels not as 'green' as many think
Statements about biofuels being carbon neutral should be taken with a grain of salt.
More Biofuels News and Biofuels Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.