ExxonMobil, the oil major behind Mobil-branded lubricants, has a broad research portfolio when it comes to biofuels. It believes some fundamental breakthroughs in science and technology are still required before advanced biofuels can be efficiently and economically produced and processed with lower greenhouse gas (GHG) emissions over their life cycles. One promising prospect being developed by ExxonMobil, alongside its partner Synthetic Genomics Inc. (SGI), is the use of algae to produce a bio-oil similar in composition to crude oil.
Why use algae?
Firstly, there is a problem with first-generation biofuels (i.e. those made from edible crops like corn). While many researchers agree that the direct GHG emissions over the life cycle are lower than those of fossil fuels, the indirect consequences of developing such fuels (e.g. deforestation and land-use changes) may mean their overall life cycle GHG emissions are actually higher than with fossil fuels.
A second-generation fuel like algae oil brings a number of advantages. Firstly, algae can be cultivated on land that would otherwise be unused, so there’s no necessary change in land use and algae could potentially deliver more biofuel per unit of land than existing sources. Secondly, algae do not require fresh water, so it’s not taking any away from normal food production. In addition, algae consume carbon dioxide, thus offsetting the emissions when the oil is consumed as fuel. The predicted result, according to ExxonMobil and SGI, will be a fuel with 50% lower life cycle GHG emissions than fossil fuels.
How does algae produce oil?
Algae is actually a very diverse non-food source of many desirable molecules. While some strains can produce fermentable sugars, others produce something resembling crude oil in its composition. The challenge that ExxonMobil and SGI faced was to optimise a strain of algae so it could produce more oil while also maintaining rapid growth. These are the two all-important requirements for producing oil in a scalable and efficient manner.
While increasing oil production can be achieved by limiting nutrients, it can also stall the algae’s growth and eventually cause a drop in production. In response to this challenge, the team at ExxonMobil and SGI successfully modified a strain of algae and doubled its oil content from 20% to 40%.
This breakthrough may be an important step in finding a viable alternative to crude oil. In addition to its ability to grow in salt water and harsh conditions, the oil from algae can potentially be processed in existing refineries to make bio-diesel, reducing the need for new infrastructure. What’s more, it could also be a potential feedstock for the chemical industry, and maybe it will be used one day in popular Mobil lubricants like DTE 24.
Work remains to be done, of course. ExxonMobil and SGI say they are now looking to address the inefficient use of light by algae. By improving the efficiency of photosynthesis in individual algae cells, the team hope to create cells that only absorb as much light as they can use effectively. This would mean more light for other algae cells and greater overall oil production.