̽��ֱ�� of Cambridge - bioenergy

Tiny ‘skyscrapers’ help bacteria convert sunlight into electricity

sc604 — Mon, 07 Mar 2022 16:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used 3D printing to create grids of high-rise ‘nano-housing’ where sun-loving bacteria can grow quickly. ̽��ֱ��researchers were then able to extract the bacteria’s waste electrons, left over from photosynthesis, which could be used to power small electronics.

Other research teams have extracted energy from photosynthetic bacteria, but the Cambridge researchers have found that providing them with the right kind of home increases the amount of energy they can extract by over an order of magnitude. ̽��ֱ��approach is competitive against traditional methods of renewable bioenergy generation and has already reached solar conversion efficiencies that can outcompete many current methods of biofuel generation.

Their results, reported in the journal Nature Materials, open new avenues in bioenergy generation and suggest that ‘biohybrid’ sources of solar energy could be an important component in the zero-carbon energy mix.

Current renewable technologies, such as silicon-based solar cells and biofuels, are far superior to fossil fuels in terms of carbon emissions, but they also have limitations, such as a reliance on mining, challenges in recycling, and a reliance on farming and land use, which results in biodiversity loss.

“Our approach is a step towards making even more sustainable renewable energy devices for the future,” said Dr Jenny Zhang from the Yusuf Hamied Department of Chemistry, who led the research.

Zhang and her colleagues from the Department of Biochemistry and the Department of Materials Science and Metallurgy are working to rethink bioenergy into something that is sustainable and scalable.

Photosynthetic bacteria, or cyanobacteria, are the most abundant life from on Earth. For several years, researchers have been attempting to ‘re-wire’ the photosynthesis mechanisms of cyanobacteria in order to extract energy from them.

“There’s been a bottleneck in terms of how much energy you can actually extract from photosynthetic systems, but no one understood where the bottleneck was,” said Zhang. “Most scientists assumed that the bottleneck was on the biological side, in the bacteria, but we’ve found that a substantial bottleneck is actually on the material side.”

In order to grow, cyanobacteria need lots of sunlight – like the surface of a lake in summertime. And in order to extract the energy they produce through photosynthesis, the bacteria need to be attached to electrodes.

̽��ֱ��Cambridge team 3D-printed custom electrodes out of metal oxide nanoparticles that are tailored to work with the cyanobacteria as they perform photosynthesis. ̽��ֱ��electrodes were printed as highly branched, densely packed pillar structures, like a tiny city.

Zhang’s team developed a printing technique that allows control over multiple length scales, making the structures highly customisable, which could benefit a wide range of fields.

“ ̽��ֱ��electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” said Zhang. “Cyanobacteria need something they can attach to and form a community with their neighbours. Our electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper.”

Once the self-assembling cyanobacteria were in their new ‘wired’ home, the researchers found that they were more efficient than other current bioenergy technologies, such as biofuels. ̽��ֱ��technique increased the amount of energy extracted by over an order of magnitude over other methods for producing bioenergy from photosynthesis.

“I was surprised we were able to achieve the numbers we did – similar numbers have been predicted for many years, but this is the first time that these numbers have been shown experimentally,” said Zhang. “Cyanobacteria are versatile chemical factories. Our approach allows us to tap into their energy conversion pathway at an early point, which helps us understand how they carry out energy conversion so we can use their natural pathways for renewable fuel or chemical generation.”

̽��ֱ��research was supported in part by the Biotechnology and Biological Sciences Research Council, the Cambridge Trust, the Isaac Newton Trust and the European Research Council. Jenny Zhang is BBSRC David Phillips Fellow in the Department of Chemistry, and a Fellow of Corpus Christi College, Cambridge.

Reference:
Xiaolong Chen et al. ‘3D-printed hierarchical pillar array electrodes for high performance semi-artificial photosynthesis.’ Nature Materials (2022). DOI: 10.1038/s41563-022-01205-5

Researchers have made tiny ‘skyscrapers’ for communities of bacteria, helping them to generate electricity from just sunlight and water.

Our approach is a step towards making even more sustainable renewable energy devices for the future

Jenny Zhang

Gabriella Bocchetti

3D-printed custom electrodes

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Scientists aim to improve photosynthesis to increase food and fuel production

gm349 — Mon, 11 Apr 2011 10:16:04 +0000

Two new initiatives at the ̽��ֱ�� of Cambridge aim to address the growing demand on the Earth’s resources for food and fuel by improving the process of photosynthesis.

As part of a new collaboration, the scientists have been awarded the major component of a $4M initiative to improve the process of photosynthesis, which allows biological systems to convert sunlight into food and is also the source of fossil fuels.

Four transatlantic research teams - two of which include academics from Cambridge’s Department of Plant Sciences - will explore ways to overcome limitations in photosynthesis which could then lead to ways of significantly increasing the yield of important crops for food production or sustainable bioenergy.

Professor Howard Griffiths from the Department of Plant Sciences said: “Plants really matter, and for the next generation, plant and microbial productivity will become the focus of key global issues: the basis for feeding an additional 2-3 billion mouths, to drive forward an economy currently trading on past sunlight, and maintain biodiversity in the face of climate change.”

̽��ֱ��funding has been awarded by the UK Biotechnology and Biological Sciences Research Council (BBSRC) and the US National Science Foundation (NSF) in a pioneering undertaking for the best minds from the USA and UK to join forces to explore this important research.

Despite the fact that photosynthesis is the basis of energy capture from the sun in plants, algae and other organisms, it has some fundamental limitations. There are trade-offs in nature which mean that photosynthesis is not as efficient as it could be - for many important crops such as wheat, barley, potatoes and sugar beet, the theoretical maximum is only 5%, depending on how it is measured. There is scope to improve it for processes useful to us, for example increasing the amount of food crop or energy biomass a plant can produce from the same amount of sunlight.

Some of the research will focus on improving a reaction driven by an enzyme called Rubisco, which is a widely recognised bottleneck in the photosynthesis pathway. By attempting to transfer parts from algae and bacteria into plants, the researchers hope to make the environment in the plants' cells around Rubisco richer in carbon dioxide which will allow photosynthesis to produce sugars more efficiently.

Professor Griffiths added: “ ̽��ֱ��enzymatic powerhouse Rubisco takes carbon dioxide from the atmosphere and uses light energy to produce sugars and other building blocks of life. However, the enzyme is rather flawed and somewhat promiscuous: it engages with oxygen as well as carbon dioxide, to the detriment of potential plant productivity.

“Some plants have evolved mechanisms, which act like biological turbochargers, to concentrate CO2 around Rubisco and improve the enzyme’s operating efficiency. These carbon concentrating mechanisms have evolved in certain key crops, such as sugar cane and maize. Other plants, such as aquatic algae, have developed mechanism in parallel which actively concentrate bicarbonate as a source of CO2 for Rubisco.”

̽��ֱ��research projects have been funded by BBSRC and NSF following a multidisciplinary workshop held by the funders in California in September 2010. ̽��ֱ��workshop, called the Ideas Lab, enabled scientists from different disciplines and institutions in the UK and USA to explore ideas and potential projects before submitting them to BBSRC and NSF.

̽��ֱ��Ideas Lab experience was likened by Professor Griffiths to be a combination of Big Brother, ̽��ֱ��Weakest Link and ̽��ֱ��Apprentice. Professor Griffiths is the consortium leader for one of the joint proposals funded, which will be exploring the operation of an algal carbon concentrating mechanism, and the possibility for introducing components into higher plant cells.

Dr Julian Hibberd from the Department of Plant Sciences is part of one of the other initiatives which is seeking to increase the efficiency of light harvesting by broadening the wavelengths of light, as used by bacteria, to power biophysical transport processes in higher plants.

This research will consolidate a major Plant Sciences initiative at Cambridge, which is exploring the means to improve photosynthesis from the perspective of sustainable plant productivity and crop yields for the future. Additional work is also being undertaken by Dr Hibberd to investigate the potential introduction of C4 photosynthetic traits into crops such as rice. This programme is part of a broader sweep of strategic research relevant to sustainable crop development, involving RNAi, pathogen suppression and epidemiological controls to maintain yields in a changing climate.

New collaboration aims to address the growing demand for food and fuel by improving the process of photosynthesis.

Plants really matter, and for the next generation, plant and microbial productivity will become the focus of key global issues: the basis for feeding an additional 2-3 billion mouths, to drive forward an economy currently trading on past sunlight, and maintain biodiversity in the face of climate change.

Professor Howard Griffiths

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Stooks

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Bioenergy research blooms in Cambridge

bjb42 — Sun, 01 Aug 2010 14:41:57 +0000

Plants are the most important natural resource on the planet. Not only do they provide all the food we eat, either directly or indirectly as animal feed, but they are also an important source of building materials and biopolymers, such as rubber, as well as many important pharmaceutical products.

Now plants are increasingly being exploited as a source of renewable energy. Plants harness solar radiation by photosynthesis; because this fixes atmospheric CO₂ to produce biomass, using plants as a source of energy is potentially carbon neutral. In addition, compared with other sources of renewable energy, biofuels also offer the major advantage of providing a source of liquid fuel, which is required for transport.

But biofuels have also come under criticism. So-called first-generation biofuels are produced by fermentation of starch from crops such as maize to yield ethanol, or are derived from plant oils yielding biodiesel. Although the amounts produced are small (approximately 3% of European transport fuel energy consumption comes from first-generation biofuels), the use of food crops as a source of raw materials at a time when populations are increasing in size has led to a ‘food versus fuel’ debate.

Sources of alternative biofuel feedstock that don’t compete with food production are needed. Within the past two years, scientists from several Cambridge departments have come together to form the Bioenergy Initiative to explore the potential of next-generation biofuels. These interdisciplinary collaborations are tackling the technical and environmental obstacles that must be addressed to make next-generation biofuels commercially viable. ̽��ֱ��research is focusing on two main areas: developing fuels based on non-food crops and the parts of food crops that are normally discarded as waste, and developing ways of harvesting energy from algae.

Plants for bioenergy

Plant material such as wood and straw has the potential to be part of the low carbon solution to replace our fossil-fuel-based liquid transport fuels, provided an environmentally, socially and economically sustainable production method is found. Plants store most of the carbon they take from the atmosphere in their cell walls as polysaccharides. Instead of burning plants to release energy, the plant biomass could be more usefully converted to liquid fuels such as ethanol by chemically releasing these sugars, and then using microbes to ferment them to fuels. This requires that as much as possible of the cell wall polysaccharides are used, with minimal expenditure of energy and minimal use of expensive chemical and enzymatic treatment to extract them. Much research is needed to make this an industrial reality.

Early in 2009, the UK Biotechnology and Biological Sciences Research Council (BBSRC) announced a £27 million investment in research in this area. ̽��ֱ��new virtual BBSRC Sustainable Bioenergy Centre (BSBEC) is a partnership of six research hubs and industry. As part of this, Dr Paul Dupree in the Department of Biochemistry leads the BSBEC Cell Wall Sugars Programme in Cambridge. ̽��ֱ��Programme aims to improve the energy conversion process by understanding how sugars are locked into the plant biomass.

Up to 10 million tonnes of wheat straw could be available in the UK each year for energy production. If converted to ethanol, this could generate a few percent of UK transport fuel requirements. Increases beyond this are possible if crops such as willow or Miscanthus grass are grown on land that is unsuitable for food crops. Cambridge BSBEC researchers are contributing to studies on the farming of these crops at Rothamsted Research, Hertfordshire, to improve yields and to understand how to optimise sustainability of the crops in terms of energy input and biodiversity.

By analysing how sugars are locked into plant cell walls, research in the Dupree group aims to identify the best plants and the right enzymes to release the maximum amount of sugars for conversion to biofuels. ̽��ֱ��research team is building links with industry and other research centres to ensure their findings will increase the sustainable use of plants for fuels and other renewable products.

Pond slime to the rescue

̽��ֱ��other major strand of research being undertaken in the Initiative has focused on algae. These simple aquatic plants are responsible for an estimated 50% of global carbon fixation and offer considerable advantages compared with biofuels from land crops. Many species are able to produce high levels of hydrocarbons, and they can also divert photosynthetic energy into another ready-to-use fuel, hydrogen. Algal productivity can be much higher than that of land plants per unit area, because of their fast growth rates, and they can be grown on marginal land, or even offshore, where they don’t compete with food crops.

However, there is little or no infrastructure for the cultivation and harvesting of microalgae on a large scale, apart from commercial operations employed for the production of high-value products such as the food supplement astaxanthin, which is used in the fish industry. Moreover, for fuel production, cost margins are critical, and most importantly the energy that is obtained from the fuel extracted must be greater than that used in the process. To address some of the many difficulties that will be encountered in attempts to commercialise biofuel production from algae, the Algal Bioenergy Consortium (ABC) was founded in 2007 by Professor Alison Smith (Department of Plant Sciences), together with Professor Chris Howe (Biochemistry), Dr John Dennis (Chemical Engineering and Biotechnology) and Dr Stuart Scott (Engineering).

A major issue is which algal species to grow. Although most people are familiar with the two broad categories of algae – seaweed on the beach or the scum that grows on ponds or on the patio – the algal kingdom is incredibly diverse. However, our knowledge of algal biology in general is poor, and we know even less about how these organisms would behave in the large-scale dense cultures that would be needed for biofuel feedstock production.

̽��ֱ��research focus of the ABC is to study a few species in depth, taking advantage of molecular tools that are being developed for some model species. Through studying ways in which algae make fuel molecules and how the algal cell wall is built, the researchers aim to discover ways to increase the extraction of fuel molecules with maximum yields.

Together with Dr Adrian Fisher in the Department of Chemical Engineering and Biotechnology, the ABC is also investigating ways of harvesting hydrogen as an energy source in a biophotovoltaic device. ̽��ֱ��method is based on ‘stealing’ electrons from the photosynthetic process. Although currents so far are low, with funding from the Engineering and Physical Sciences Research Council (EPSRC) and the formation of a ̽��ֱ�� spin-out, H+ Energy, the combination of biological and engineering approaches is helping to optimise the prototypes.

Part of the energy spectrum

At the present time, an estimated 1 million years’ worth of fossil fuel deposition is consumed each year. As fossil fuels become scarcer and more expensive to extract, and carbon emissions increase as a result of their use, renewable sources of energy will be essential. Given the size of the challenge to provide energy security in a sustainable way, it is important to explore the entire spectrum of possible energy sources. Biofuels from plants and algae have the potential to offer both a sustainable and carbon-neutral supply, but many hurdles need to be overcome before this potential is realised. With the critical mass of bioenergy researchers now working in Cambridge, the Bioenergy Initiative has the opportunity to play a major role in tackling these issues.

For more information, please contact the authors Professor Alison Smith (as25@cam.ac.uk) at the Department of Plant Sciences and Dr Paul Dupree (pd101@cam.ac.uk) at the Department of Biochemistry, or visit www.bioenergy.cam.ac.uk/

̽��ֱ��Bioenergy Initiative is bringing biology and engineering together to address the challenge of meeting our future energy needs.

Alison Smith

Algae

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