In 2010 the Deepwater Horizon oil spill released an estimated 4.2 million barrels of oil into the Gulf of Mexico – the largest offshore spill in U.S. history. The spill caused widespread damage to marine species, fisheries and ecosystems stretching from tidal marshes to the deep ocean floor.
Emergency responders used multiple strategies to remove oil from the Gulf: They skimmed it from the water’s surface, burned it and used chemical dispersants to break it into small droplets. However, experts struggled to account for what had happened to much of the oil. This was an important question, because it was unclear how much of the released oil would break down naturally within a short time. If spilled oil persisted and sank to the ocean floor, scientists expected that it would cause more extensive harm to the environment.
Before the Deepwater Horizon spill, scientists had observed that marine bacteria were very efficient at removing oil from seawater. Therefore, many experts argued that marine microbes would consume large quantities of oil from the BP spill and help the Gulf recover.
In a recent study, we used DNA analysis to confirm that certain kinds of marine bacteria efficiently broke down some of the major chemical components of oil from the spill. We also identified the major genetic pathways these bacteria used for this process, and other genes, which they likely need to thrive in the Gulf.
Altogether, our results suggest that some bacteria can not only tolerate but also break up oil, thereby helping in the cleanup process. By understanding how to support these natural occurring microbes, we may also be able to better manage the aftermath of oil spills.
Finding the oil-eaters
Observations in the Gulf appeared to confirm that microbes broke down a large fraction of the oil released from BP’s damaged well. Before the spill, waters in the Gulf of Mexico contained a highly diverse range of bacteria from several different phyla, or large biological families. Immediately after the spill, these bacterial species became less diverse and one phylum increased substantially in numbers. This indicated that many bacteria were sensitive to high doses of oil, but a few types were able to persist.
We wanted to analyze these observations more closely by posing the following questions: Could we show that these bacteria removed oil from the spill site and thereby helped the environment recover? Could we decipher the genetic code of these bacteria? And finally, could we use this genetic information to understand their metabolisms and lifestyles?
To address these questions, we used new technologies that enabled us to sequence the genetic code of the active bacterial community that was present in the Gulf of Mexico’s water column, without having to grow them in the laboratory. This process was challenging because there aremillions of bacteria in every drop of seawater. As an analogy, imagine looking through a large box that contains thousands of disassembled jigsaw puzzles, and trying to extract the pieces belonging to each individual puzzle and reassemble it.
We wanted to identify bacteria that could degrade two types of compounds that are the major constituents of crude oil: alkanes and aromatic hydrocarbons. Alkanes are relatively easy to degrade – even sunlight can break them down – and have low toxicity. In contrast, aromatic hydrocarbons are much harder to remove from the environment. They are generally much more harmful to living organisms, and some types cause cancer.
We successfully identified bacteria that degraded each of these compounds, and were surprised to find that many different bacteria fed on aromatic hydrocarbons, even though these are much harder to break down. Some of these bacteria, such as Colwellia, had already been identified as factors in the degradation of oil from the Deepwater Horizon spill, but we also found many new ones.
This included Neptuniibacter, which had not previously been known as an important oil-degrader during the spill, and Alcanivorax, which had not been thought to be capable of degrading aromatic hydrocarbons. Taken together, our results indicated that many different bacteria may act together as a community to degrade complex oil mixtures.
Neptuniibacter also appears to be able to break down sulfur. This is noteworthy because responders used 1.84 million gallons of dispersantson and under the water’s surface during the Deepwater Horizon cleanup effort. Dispersants are complex chemical mixtures but mostly consist of molecules that contain carbon and sulfur.
Their long-term impacts on the environment are still largely unknown. But some studies suggest that Corexit, the main dispersant used after the Deepwater Horizon spill, can be harmful to humans and marine life. If this proves true, it would be helpful to know whether some marine microbes can break down dispersant as well as oil.
Looking more closely into these microbes' genomes, we were able to detail the pathways that each appeared to use in order to degrade its preferred hydrocarbon in crude oil. However, no single bacterial genome appeared to possess all the genes required to completely break down the more stable aromatic hydrocarbons alone. This implies that it may require a diverse community of microbes to break down these compounds step by step.
Back into the ocean
Offshore drilling is a risky activity, and we should expect that oil spills will happen again. However, it is reassuring to see that marine ecosystems have the ability to degrade oil pollutants. While human intervention will still be required to clean up most spills, naturally occurring bacteria have the ability to remove large amounts of oil components from seawater, and can be important players in the oil cleanup process.
To maximize their role, we need to better understand how we can support them in what they do best. For example, adding dispersant changed the makeup of microbial communities in the Gulf of Mexico during the spill: the chemicals were toxic to some bacteria but beneficial for others. With a better understanding of how human intervention affects these bacteria, we may be able to support optimal bacteria populations in seawater and reap more benefit from their natural oil-degrading abilities.
Postdoctoral Fellow, University of Texas at Austin
Assistant Professor of Marine Science, University of Texas at Austin
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In 2021, the makeup of renewables has also changed drastically. Technologies such as solar and wind are no longer novel, as is the idea of blending vegetable oils into road fuels or switching to electric-based vehicles. Such ideas are now entrenched and are not considered enough to shift the world into a carbon neutral future. The new wave of renewables focus on converting by-products from other carbon-intensive industries into usable fuels. Research into such technologies has been pioneered in universities and start-ups over the past two decades, but the impetus of global climate goals is now seeing an incredible amount of money being poured into them as oil & gas giants seek to rebalance their portfolios away from pure hydrocarbons with a goal of balancing their total carbon emissions in aggregate to zero.
Traditionally, the European players have led this drive. Which is unsurprising, since the EU has been the most driven in this acceleration. But even the US giants are following suit. In the past year, Chevron has poured an incredible amount of cash and effort in pioneering renewables. Its motives might be less than altruistic, shareholders across America have been particularly vocal about driving this transformation but the net results will be positive for all.
Chevron’s recent efforts have focused on biomethane, through a partnership with global waste solutions company Brightmark. The joint venture Brightmark RNG Holdings operations focused on convert cow manure to renewable natural gas, which are then converted into fuel for long-haul trucks, the very kind that criss-cross the vast highways of the US delivering goods from coast to coast. Launched in October 2020, the joint venture was extended and expanded in August, now encompassing 38 biomethane plants in seven US states, with first production set to begin later in 2021. The targeting of livestock waste is particularly crucial: methane emissions from farms is the second-largest contributor to climate change emissions globally. The technology to capture methane from manure (as well as landfills and other waste sites) has existed for years, but has only recently been commercialised to convert methane emissions from decomposition to useful products.
This is an arena that another supermajor – BP – has also made a recent significant investment in. BP signed a 15-year agreement with CleanBay Renewables to purchase the latter’s renewable natural gas (RNG) to be mixed and sold into select US state markets. Beginning with California, which has one of the strictest fuel standards in the US and provides incentives under the Low Carbon Fuel Standard to reduce carbon intensity – CleanBay’s RNG is derived not from cows, but from poultry. Chicken manure, feathers and bedding are all converted into RNG using anaerobic digesters, providing a carbon intensity that is said to be 95% less than the lifecycle greenhouse gas emissions of pure fossil fuels and non-conversion of poultry waste matter. BP also has an agreement with Gevo Inc in Iowa to purchase RNG produced from cow manure, also for sale in California.
But road fuels aren’t the only avenue for large-scale embracing of renewables. It could take to the air, literally. After all, the global commercial airline fleet currently stands at over 25,000 aircraft and is expected to grow to over 35,000 by 2030. All those planes will burn a lot of fuel. With the airline industry embracing the idea of AAF (or Alternative Aviation Fuels), developments into renewable jet fuels have been striking, from traditional bio-sources such as palm or soybean oil to advanced organic matter conversion from agricultural waste and manure. Chevron, again, has signed a landmark deal to advance the commercialisation. Together with Delta Airlines and Google, Chevron will be producing a batch of sustainable aviation fuel at its El Segundo refinery in California. Delta will then use the fuel, with Google providing a cloud-based framework to analyse the data. That data will then allow for a transparent analysis into carbon emissions from the use of sustainable aviation fuel, as benchmark for others to follow. The analysis should be able to confirm whether or not the International Air Transport Association (IATA)’s estimates that renewable jet fuel can reduce lifecycle carbon intensity by up to 80%. And to strengthen the measure, Delta has pledged to replace 10% of its jet fuel with sustainable aviation fuel by 2030.
In a parallel, but no less pioneering lane, France’s TotalEnergies has announced that it is developing a 100% renewable fuel for use in motorsports, using bioethanol sourced from residues produced by the French wine industry (among others) at its Feyzin refinery in Lyon. This, it believes, will reduce the racing sports’ carbon emissions by an immediate 65%. The fuel, named Excellium Racing 100, is set to debut at the next season of the FIA World Endurance Championship, which includes the iconic 24 Hours of Le Mans 2022 race.
But Chevron isn’t done yet. It is also falling back on the long-standing use of vegetable oils blended into US transport fuels by signing a wide-ranging agreement with commodity giant Bunge. Called a ‘farmer-to-fuelling station’ solution, Bunge’s soybean processing facilities in Louisiana and Illinois will be the source of meal and oil that will be converted by Chevron into diesel and jet fuel. With an investment of US$600 million, Chevron will assist Bunge in doubling the combined capacity of both plants by 2024, in line with anticipated increases in the US biofuels blending mandates.
Even ExxonMobil, one of the most reticent of the supermajors to embrace renewables wholesale, is getting in on the action. Its Imperial Oil subsidiary in Canada has announced plans to commercialise renewable diesel at a new facility near Edmonton using plant-based feedstock and hydrogen. The venture does only target the Canadian market – where political will to drive renewable adoption is far higher than in the US – but similar moves have already been adopted by other refiners for the US market, including major investments by Phillips 66 and Valero.
Ultimately, these recent moves are driven out of necessity. This is the way the industry is moving and anyone stubborn enough to ignore it will be left behind. Combined with other major investments driven by European supermajors over the past five years, this wider and wider adoption of renewable can only be better for the planet and, eventually, individual bottom lines. The renewables ball is rolling fast and is only gaining momentum.
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