Breakthroughs in renewable biofuels production

*Water evaporation could provide vast amounts of green energy, scientists find

Scientists have made giant strides towards biofuels production and other renewable energy sources.Researchers at Chalmers University of Technology, Sweden, have identified two main challenges for renewable biofuel production from cheap sources. Firstly, lowering the cost of developing microbial cell factories, and secondly, establishing more efficient methods for hydrolysis of biomass to sugars for fermentation. Their study was recently published in the journal Nature Energy.

Also, a machine has been invented that can turn the movement of bacterial spores as air humidity changes into electricity.Indeed, scientists have discovered a new source of vast amounts of renewable energy –the evaporation of water.

Writing in the journal Nature Communications, researchers at Columbia University estimated that lakes in the US could generate 325 gigawatts of power, equivalent to about 70 per cent of the country’s total electricity generation.While they cautioned that the devices capable of turning water evaporation into electricity were still being developed, the scientists said their new analysis showed the enormous potential.

The first study published in the journal Nature Energy, 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.

“Our study is of particular interest for decision makers and research funders, as it highlights recent advances and the potential in the field of biofuels. It also identifies where more research is required. This can help to prioritise what research should be funded,” says Eduard Kerkhoven.

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 — as well as being noted for their world-class research into human metabolism, and investigations into aging processes and diseases. Their work informs how yeast can best be engineered to manufacture new chemicals or biofuels. In their article “Barriers and opportunities in bio-based production of hydrocarbons,” the researchers investigate the production of various biofuels using a model of yeast metabolism.

“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,” says Eduard Kerkhoven.

The other main barrier is efficient conversion from biomass, such as plants and trees, 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. Eduard Kerkhoven notes how important biofuels will be for the future.

“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 percent of all global end energy-use by the end of the century. That is in line with our research too,” he concludes.

Meanwhile, Prof. Ozgur Sahin, a biophysicist involved in the research published in journal Nature Communications, said: “We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful. We can now put a number on its potential.”

His laboratory has developed one kind of ‘evaporation engine’, which works by using the movement of bacteria in response to changes in humidity.

Shutters either opened or closed to control moisture levels, prompting bacterial spores to expand or contract. This motion is then transferred to a generator and turned into electricity.

“Although these evaporation energy harvesters are in the early stages of development, recent advances water-responsive materials and devices suggest several pathways toward achieving the predicted performance levels,” the Nature Communications paper said.

“With advances in energy conversion performance, these materials and devices could potentially contribute toward solving energy and water-related challenges.”However, it was “important to note” that harnessing this source of energy could affect water quality, recreation on lakes and other “freshwater resources”, the scientists cautioned.

But they also said the machines might reduce the loss of water in areas prone to drought.“These consequences would impose additional design and planning constraints on such systems that could reduce the area available for energy harvesting,” they said.

“However, the potential area available for open water energy harvesting is substantial – lakes and reservoirs cover at least 95,000 square kilometres (excluding the Great Lakes) of the contiguous United States – and are found across a geographically diverse range of locations.

“Some of these regions suffer from periods of water stress and scarcity, which might favour implementation of these energy harvesting systems due to the reduction of evaporative losses.”

The researchers calculated that this could save 25 trillion gallons a year, about a fifth of the water consumed by Americans. California, Nevada and Arizona, where droughts are becoming an increasing problem, would benefit the most.They also said the devices could help overcome the intermittency of other renewable sources of power, such as solar and wind.

“Evaporation comes with a natural battery,” said researcher Ahmet-Hamdi Cavusoglu, a graduate student at Columbia. “You can make it your main source of power and draw on solar and wind when they’re available.”

Professor Klaus Lackner, a physicist at Arizona State University who was not involved in the study, is currently developing artificial trees that draw carbon dioxide from the air, partly by using evaporation.“Evaporation has the potential to do a lot of work,” he said.
“It’s nice to see that drying and wetting cycles can also be used to collect mechanical energy.”