With gas prices soaring and food costs pinching family budgets, an interdisciplinary team of researchers at WPI is looking at ways to use food waste to make a renewable and more affordable fuel replacement for oil-based diesel. The work, led by Chemical Engineering Professor Michael Timko, is detailed in a new paper in the journal iScience.
Geissler, C.H. and Maravelias, C.T. (2022). “Analysis of alternative bioenergy with carbon capture strategies: present and future.” Energy & Environmental Science 5, 2679-2689. https://doi.org/10.1039/D2EE00625A [open access]
Abstract: Biomass can be converted via fermentation, pyrolysis, gasification, or combustion to a variety of bioenergies, and each conversion technology generates streams with different flows and CO2 concentrations that can undergo carbon capture. We use system-wide optimization models to determine the conversion technologies and level of carbon capture that lead to the minimum breakeven cost of fuel for a range of capacities and sequestration credits. We investigate how the optimal systems depend on constraints, such as energetic biorefinery self-sufficiency; and parameters, such as biomass availability. Pyrolysis to gasoline/diesel with hydrogen purchase produces liquid fuel for the lowest cost when energy purchase is allowed, with flue gas capture incentivized at sequestration credits of $48–54 per Mg CO2. With increasing sequestration credits, gasification to gasoline/diesel with carbon capture becomes optimal. When all bioenergies are considered, the cost per forward motion of electricity and hydrogen is lower than for liquid fuels because of the higher efficiency of electric motors and hydrogen fuel cells. We find that while gasification to electricity results in the greatest greenhouse gas mitigation under the current energy production mix, gasification to hydrogen is expected to result in the greatest mitigation in the future as the energy production mix changes.
Broader context: Bioenergy with carbon capture and sequestration (BECCS) is expected to be pivotal in global warming mitigation. BECCS systems include conversion technologies such as fermentation to ethanol, pyrolysis to gasoline/diesel, gasification to gasoline, combustion to electricity, and gasification to electricity or hydrogen. However, it is not yet clear which of these different conversion technologies with integrated carbon capture has the greatest economic and CO2 mitigation potential. Accordingly, we determine the cost-optimal BECCS strategy under a wide range of scenarios and assumptions. Looking into the future, we present the expected mitigation potential of the most promising BECCS strategies through 2050.
The bioeconomy – the part of the economy driven by the life sciences and biotech, and enabled by engineering, computing, and information science – has the potential to revolutionize human health, climate and energy, food security and sustainability, and supply chain stability, as well as support economic growth and well-paying jobs across the entire country. The U.S. government has recognized this exceptional promise: The recent Executive Order on advancing the U.S. bioeconomy and relevant provisions in the CHIPS and Science Law and the Inflation Reduction Law have opened up an excellent opportunity to engage with the U.S. government to help develop and shape the implementation of policies to bolster the economic engine that is the biotech and biomanufacturing ecosystem.
The Day One Project now needs your help to generate innovative, specific, and actionable policy ideas that the U.S. government could use to supercharge the U.S. bioeconomy.
They are particularly focused on:
Leveraging financial or economic tools – such as loan programs, tax incentives, demand-pull mechanisms, and economic development challenges – to support and advance the U.S. bioeconomy in ways that enable and incentivize biotech or biomanufacturing to expand into new regions of the U.S., build new facilities, and engage in workforce development efforts;
Enabling better measurement of the U.S. bioeconomy’s contributions to the rest of the economy; and
Devising new authorities that may be needed at federal agencies in order to support a maximally-coordinated effort to advance the U.S. bioeconomy.
Submit your idea here. Submissions are due Monday, November 7th, and will be reviewed on a rolling basis, so submit today!
When United Airlines took off from Chicago for Washington, DC last December, it landed a significant development: the use of 100% sustainable aviation fuel. The goal is that biofuels will fully power the airline industry by 2050.
Corn-based ethanol may have worse environmental impacts than fossil fuels, according to a new study that concludes the United States biofuel program has failed to meet emissions targets while delivering negatives impacts on water quality, land used for conservation, and other ecosystem processes.
If you’ve pumped gas at a U.S. service station over the past decade, you’ve put biofuel in your tank. Thanks to the federal Renewable Fuel Standard, or RFS, almost all gasoline sold nationwide is required to contain 10% ethanol – a fuel made from plant sources, mainly corn.
Enacted in the wake of the attacks of Sept. 11, 2001, the RFS promised to enhance energy security, cut carbon dioxide emissions and boost income for rural America. The program has certainly raised profits for portions of the agricultural industry, but in my view it has failed to fulfill its other promises. Indeed, studies by some scientists, including me, find that biofuel use has increased rather than decreased CO2 emissions to date.
Current law sets a target of producing and using 36 billion gallons of biofuels by 2022 as part of the roughly 200 billion gallons of motor fuel that U.S. motor vehicles burn each year. As of 2019, drivers were using only 20 billion gallons of renewable fuels yearly – mainly corn ethanol and soybean biodiesel. Usage declined in 2020 because of the pandemic, as did most energy use. Although the 2021 tally is not yet complete, the program remains far from its 36 billion-gallon goal. I believe the time is ripe to repeal the RFS, or at least greatly scale it back.
Higher profits for many farmers
The RFS’s clearest success has been boosting income for corn and soybean farmers and related agricultural firms. It also has built up a sizable domestic biofuel industry.
The Renewable Fuels Association, a trade group for the biofuels industry, estimates that the RFS has generated over 300,000 jobs in recent years. Two-thirds of these jobs are in the top ethanol-producing states: Iowa, Nebraska, Illinois, Minnesota, Indiana and South Dakota. Given Iowa’s key role in presidential primaries, most politicians with national ambitions find it prudent to embrace biofuels.
For consumers, biofuel use has had a varying, but overall small, effect on pump prices. Renewable fuel policy has little leverage in the world oil market, where the biofuel mandate’s penny-level effects are no match for oil’s dollar-scale volatility.
Biofuels are not carbon-neutral
The idea that biofuels are good for the environment rests on the assumption that they are inherently carbon neutral – meaning that the CO2 emitted when biofuels are burned is fully offset by the CO2 that feedstocks like corn and soybeans absorb as they grow. This assumption is coded into computer models used to evaluate fuels.
Leading up to passage of the RFS, such modeling found modest CO2 reductions for corn ethanol and soybean biodiesel. It promised greater benefits from cellulosic ethanol – a more advanced type of biofuel that would be made from nonfood sources, such as crop residues and energy crops like willow and switchgrass.
One big factor is that making biofuels amplifies land-use change. As harvests are diverted from feeding humans and livestock to produce fuel, additional farmland is needed to compensate. That means forests are cut down and prairies are plowed up to carve out new acres for crop production, triggering very large CO2 releases.
When Congress expanded the biofuel mandate in 2007, a key factor that induced legislators from states outside the Midwest to support it was the belief that a coming generation of cellulosic ethanol would produce even greater environmental, energy and economic benefits. Biofuel proponents claimed that cellulosic fuels were close to becoming commercially viable.
Almost 15 years later, in spite of the mandate and billions of dollars in federal support, cellulosic ethanol has flopped. Total production of liquid cellulosic biofuels has recently hovered around 10 million gallons per year – a tiny fraction of the 16 billion gallons that the RFS calls for producing in 2022. Technical challenges have proved to be more daunting than proponents claimed.
Environmentally speaking, I see the cellulosic failure as a relief. If the technology were to succeed, I believe it would likely unleash an even more aggressive global expansion of industrial agriculture – large-scale farms that raise only one or two crops and rely on highly mechanized methods with intensive chemical fertilizer and pesticide use. Some such risk remains as petroleum refiners invest in bio-based diesel production and producers modify corn ethanol facilities to produce biojet fuel.
Ripple effects on lands and Indigenous people
Today the vast majority of biofuels are made from crops like corn and soybeans that also are used for food and animal feed. Global markets for major commodity crops are closely coupled, so increased demand for biofuel production drives up their prices globally.
Some researchers have found that adverse effects of biofuel production on land use, crop prices and climate are much smaller than previously estimated. Nevertheless, the uncertainties surrounding land use change and net effects on CO2 emissions are enormous. The complex modeling of biofuel-related commodity markets and land utilization is impossible to verify, as it extrapolates effects across the globe and into the future.
Rather than biofuels, a much better way to address transportation-related CO2 emissions is through improving efficiency, particularly raising gasoline vehicle fuel economy while electric cars continue to advance.
A stool with two weak legs
What can we conclude from 16 years of the RFS? As I see it, two of its three policy legs are now quite wobbly: Its energy security rationale is largely moot, and its climate rationale has proved false.
Nevertheless, key agricultural interests strongly support the program and may be able to prop it up indefinitely. Indeed, as some commentators have observed, the biofuel mandate has become another agribusiness entitlement. Taxpayers probably would have to pay dearly in a deal to repeal the RFS. For the sake of the planet, it would be a cost worth paying.
The science is clear: fossil fuels are harmful to the environment. So why is it so difficult for us to stop using them? Economic reasons are at least part of the answer. From our energy grid to the manufacturing of certain textiles and other products, many parts of our society are built to use fossil fuels. Transitioning away will come at some cost.