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Chalmers team identifies two main challenges for bio-hydrocarbon fuel production from cheap sources

Researchers at Chalmers University of Technology, Sweden, have identified two main challenges for renewable biofuel production from cheap sources: lowering the cost of developing microbial cell factories; and establishing more efficient methods for hydrolysis of biomass to sugars for fermentation.

In a paper published in the journal Nature Energy, the researchers investigated the production of various biofuels using a model of yeast metabolism. They discussed how to develop novel systems and synthetic biology tools that can enable faster and cheaper construction of microbial cell factories and thereby address the first challenge, as well as recent advances in biomass processing that will likely lead to overcoming the second challenge in the near future.

The study, by Professor Jens Nielsen, Yongjin Zhou and Eduard Kerkhoven, from the Division of Systems and Synthetic Biology, evaluates the barriers that need to be overcome to make biomass-derived hydrocarbons a real alternative to fossil fuels.

It is technically already possible to produce biofuels from renewable resources by using microbes such as yeast and bacteria as tiny cell factories. However, in order to compete with fossil-derived fuels, the process has to become much more efficient. But improving the efficiency of the microbial cell factories is an expensive and time-consuming process, so speeding-up the cell factory development is therefore one of the main barriers.

Professor Jens Nielsen and his research group are world leaders in the engineering of yeast, and in the development and application of computer models of yeast metabolism. Their work informs how yeast can best be engineered to manufacture new chemicals or biofuels.

We have calculated theoretical maximum production yields and compared this to what is currently achievable in the lab. There is still huge potential for improving the process.

—Eduard Kerkhoven

Zhou

Development of a microbial cell factory for hydrocarbon production from raw materials. From a proof-of-concept stage, where preliminary pathway engineering results in low titers on a small scale, the titer, rate and yield are improved through multiple rounds of the design-build-test-learn (DBTL)-cycle. Each part of this cycle can be aided by various techniques, and innovations in these areas will speed-up and improve the efficiency of the DBTL-cycle. Further genetic engineering of the cell factory by removing competing pathways and optimizing co-factor recycling increases titers while cultures are performed on a larger scale. The final step towards industrial application is the scale-up and improvement of robustness of the cell factory that now has high titre, rate and yield on a very large scale. Zhou et al.

The other main barrier is efficient conversion of biomass to the sugars that are used by the cell factories. If this conversion were made more efficient, it would be possible to use waste material from the forest industry, or crops that are purposely grown for biofuels, to produce a fully renewable biofuel.

In the future, whilst passenger cars will be primarily electric, biofuels are going to be critical for heavier modes of transport such as jets and trucks. The International Energy Agency projects that by 2050, 27 percent of global transport fuels will be biofuels. Meanwhile, large oil companies such as Preem and Total also predict that renewable biofuels will play an important role in the future. In their Sky Scenario, Shell expects that biofuels will account for 10% of all global end energy-use by the end of the century. That is in line with our research too.

—Eduard Kerkhoven

Resources

  • Yongjin J. Zhou, Eduard J. Kerkhoven & Jens Nielsen (2018) “Barriers and opportunities in bio-based production of hydrocarbons” Nature Energy doi: 10.1038/s41560-018-0197-x

Comments

SJC

Cellulose ethanol then gasify and synthesize what is left.

HarveyD

Who wants to continue to use bio and fossil fuels?

Let's convert water, solar and wind energies to clean electricity and clean storable H2; electrify all transportation and industrial means and stop burning fuels.

SJC

We will be using liquid hydrocarbon fuels for decades to come.

Arnold

Bio fuels' technology are also and more importantly a stage in bio plastics oils and chemicals.

Engineer-Poet

Why bother growing starches for bio-ethanol and gasify the rest?  Grow cellulose and gasify the whole mess.

Fuels are simple molecules and have few specific requirements.  Building blocks for polymers, drugs and such are another matter.  That's where biology shines.  Bulk generation of fuels, where biology just adds metabolic overhead to the process losses, isn't a really good niche unless it can be made extremely cheap.  So far that cheapness is not evident.

Arnold

I don't say I quite understand but as far as I can would agree.
I wonder at what degree of climate disruption 'cheap' becomes evident.
The simple energy tasks are easily and more productively met to the required standard by other proven technologies.
Keeping the climate solution where it needs to be I.E.fossil fuels in the ground means alternative and anecdotally superior feedstock solutions from the bio feedstocks is an important contribution.

I can understand that aside from (feedstocks) supply chain guarantee there is also the no dig origin guarantee offered from bio processing.
If as the science dictates we must cease fossil carbon extraction this century, and our expectations for minimal lifestyle disruption is desired there will be a very high expectation and need to provide the biologically derived feed stocks.
The highest value will likelybe found not as electrical energy or for fuelling equipment that has proven easy to substitute .
Aircraft, are an example of higher value application of bio fuel but otherwise bio fuel use would seem to project on average as a low relative value outcome.

Engineer-Poet
I wonder at what degree of climate disruption 'cheap' becomes evident.

One measure of "cheap" is how frugal the process is with the very limited supply of fixed carbon.  Fermentation throws 1/3 of it away as CO2.  Since CO2 is the chief climate pollutant and carbon uptake is the most expensive step, waste is cost.

If as the science dictates we must cease fossil carbon extraction this century, and our expectations for minimal lifestyle disruption is desired there will be a very high expectation and need to provide the biologically derived feed stocks.

It's much worse than that.  The USA uses around 1e20 J of primary energy per year.  Even if all of the 1.3 billion tpy of biomass in the "Billion-Ton Vision" studies can be harvested sustainably, at 17.4 GJ/ton that's just 2.26e19 J in the raw biomass.  At LEAST 77% of the energy needs to come from other sources.

The heavy lifting must come from things like nuclear.  Biofuels will have their uses but they will be mostly in niche applications.

Arnold

I would hope that the need to convert the cellulose via the recently promising pathways is understood even if not discussed in this article.

While various ambitious new ideas are being trialled to convert cellulose to simple 'process feedstock, there are processes that can or could effectively utilise the residual cellulose or lignin 'waste' .

I find the tendency for comments around a particular solution to be a common simplification is an interesting observation of many discussions. But then get caught elaborating and shut down with "Too much information!"

Trying to empathise with the less informed reader when maybe it is not meant or often interpreted in that way.

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