Drop-in biofuels from microorganisms

John Love, Associate Professor in Plant and Industrial Biotechnology, Exeter University, UK

There is no single solution to meeting the need for sustainable mobility, but advanced biofuels provide one viable way to reduce carbon dioxide emissions. Shell has several advanced biofuel research and development projects that aim to improve the carbon dioxide emission reduction and sustainability offered by biofuels, including a collaboration with Exeter University, UK, on the prospect of producing "drop-in" biofuels.

We recognise that the world needs to halve its carbon dioxide emissions by 2050 to avoid the worst effects of climate change. However, actions to tackle climate change must be reconciled with population growth, economic growth and extraordinary growth in demand for energy. Demand for energy is expected to double by 2050, as the number of people on the planet grows from nearly seven billion to about nine billion and positive economic development continues apace in non-OECD countries.

The reality is that all sources of energy will be needed. For mobility, there is no silver bullet option that will deliver sustainable mobility over the coming decades. Instead, we expect to see a more diverse range of fuel and vehicle options, with the preferred set of options varying by market. All the options will be needed and all will have a place in addressing the challenge of sustainable mobility.

The internal combustion engine will continue to play an important role, especially for long-distance travel. Liquid fuels will continue to be important in the coming decades. Shell believes the biofuels available today are the most practical commercial solution for reducing carbon dioxide emissions in the transport fuel sector over the next 20 years.

But the carbon dioxide emission reduction offered by today’s biofuels varies significantly and depends on a wide range of factors, including the feedstock used and how it is processed, distributed and used. Advanced biofuels using new feedstocks such as crop waste or inedible crops (cellulosics) and new conversion processes offer the potential for even better carbon dioxide emission reductions and have improved fuel characteristics to facilitate blending with conventional fuels in higher proportions.

Shell has technical collaborations with leading biotechnology companies exploring new technology platforms for the production of advanced biofuels. These include processing technology that enables ethanol to be made from straw using enzymes (Iogen), the development of “super-enzymes” for biofuel production (Codexis) and a development effort to convert plant sugars directly into gasoline and gasoline blend components (Virent).

Research collaboration

But what if we could grow actual jet fuel, diesel or other hydrocarbon molecules? Could we use microorganisms to ingest non-food biomass to produce drop-in fuels? This may sound like science fiction, but it is the subject of intense scientific investigation, as John Love explains.

“In an ever hungrier and warmer world, growing hydrocarbons has the obvious advantage of potentially being carbon neutral,” says Love. “But, the world is hungry for food, land and liquid fuels, so a biofuel’s provenance needs to be carefully considered.

“Ethanol is a good substitute for transport fuels. There are some smart ways of making ethanol from non-food biomass, but what if we could modify organisms to produce the actual hydrocarbon molecules we currently use?”

What would have been science fiction less than a decade ago now looks like a good medium- to long-term prospect, thanks to the fast-paced developments in modern biology. A joint team from Exeter University and Shell already has benchscale fermenters producing the alkanes we use in our engines.

As the molecules are identical to their fossil-based cousins, they can be simply dropped into the current infrastructure. So, how far are we from the commercial-scale production of advanced drop-in biofuels from microorganisms?

“Commercialisation is the goal,” says Love. “Having Shell as a partner keeps us focused on that goal. The whole subject is fascinating from a purely academic perspective, but we need these fuels now, so we must maintain our commercial focus although we recognise there is still a lot of work to do.

“Shell specified the hydrocarbon molecules it would like, mainly for jet fuel and diesel, and we are exploring intelligent ways to make them using molecular genetics, genomics and synthetic biology.

"It is an ambitious target, as we need to get microorganisms to make jet-fuel and diesel molecules, which they normally would not do, and we need to get them to do it on a diet of lignocellulose (the non-food parts of plants), which they do not normally eat. We also want them to convert as much of the feedstock carbon to fuel as possible in a way that is easily manageable at a commercial scale.”

The team has been quick to establish what is possible, but needs to understand the process at a molecular level to improve its efficiency. Love explains: “It is a little like macro-scale hydrocarbon exploration. We do bio-prospecting to find our resource, sometimes based on incomplete understanding, and then we need to work hard to exploit the resource, just as appraisal wells need drilling, reservoir models need building and production facilities need constructing.

“To produce the desired molecule, we try to understand the metabolic pathways that are responsible for producing them. We then optimise that pathway in the laboratory. Once we have done this, we have established proof of principle, but there is a lot of fundamental biochemical work to do after that. Shell understands this and realises that not everything that works in the laboratory will translate to a commercial scale.

“The hydrocarbon molecules are assembled as they shuffle through a series of protein complexes. To improve the efficiency of process, we need to understand the biochemical characteristics of each protein, how they interact, what the bottlenecks to productivity are and how to remove them. We also want to maximise the conversion of feedstock to fuel.” 

Open innovation

The Shell–Exeter partnership began seven years ago with the joint funding, along with the UK Engineering and Physical Sciences Research Council, of a postdoctoral studentship. However, this quickly changed, as Love explains: “Rob Lee, Team Leader, Shell Global Solutions, and I soon realised that the traditional model of industry funding a project and being presented with the results three years later was inadequate.

“We needed a new way of working. A true partnership based on absolute trust and one in which we could test ideas and challenge each other as friends and colleagues. Shell’s open innovation strategy provided the answer. Rob and I are truly embedded in each other’s organisations.

"I am a project leader at the Shell Biodomain Innovation Centre, where I spend about one-third of my time, and Rob is an industry professor at Exeter University, where he spends one-third of his time with our microbial biofuels group.  This arrangement relies on support at the highest level in the university and Shell. This project has changed the way Exeter University views industry collaboration.

“Shell brings an industrial imperative to our work and our academic results feed straight into Shell’s research and development programme. This rapid communication means that we need to be nimble: ready to change the focus of a project at short notice. We also need to be innovative and willing to adopt the latest technologies.

“Commercialisation is Shell’s goal. My aim is to get an efficient large-scale system, but Shell has the economic insight, engineering expertise and market to make it commercial,” Love concludes.

For more information contact Rob Lee.