A study led by the US Department of Energy appears to overcome the longstanding hurdles posed by the complex fibrous structure of cellulosic biomass, which complicates its breakdown to access fermentable glucose for biofuel production.
Biotechnologies for bioenergy production (or “sustainable energy“) refer to that sector of biotech dedicated to the study of techniques and methodologies aimed at transforming biomass into fuels of biological nature (biofuel). Here, “biomass” is defined – according to the definition given by the European Parliament – as “the biodegradable fraction of products, waste, and residues from biological origin coming from agriculture, including plant and animal substances, forestry, and related industries, including fisheries and aquaculture, as well as the biodegradable portion of waste, including industrial and urban waste of biological origin” [source: “Directive (EU) of 11 December 2018 on the promotion of the use of energy from renewable sources“].
The Union Bioenergy Sustainability Report, released by the European Commission on 24 October 2023, confirms that within the EU, a significant 59% of sustainable energy consumption comes from bioenergy derived from biomass, continuing a trend observed between 2008 and 2021, during which the Union saw an overall growth of 33.5%. The same report also notes that, by the end of 2021 in the EU, the sector of solid biofuels obtained from wood residues, zootechnical waste, and plant material was leading, accounting for 70.3% of the broader bioenergy market.
TAKEAWAYS
Biotechnologies for bioenergy: the EU’s stance on biofuels for transport
Beyond the numerical data contained in the cited report, it is crucial to note that the European Union’s stance on the production of biofuels for transport has not been linear over the years, marked by varying strategies, as highlighted in the Special Report by the European Court of Auditors, published in December 2023, “The EU’s support for sustainable biofuels in transport“.
Although there is unanimity from the European Parliament and the Council in considering biofuels “an alternative to fossil fuels, thereby contributing to the reduction of greenhouse gas emissions produced by the transport sector,” the domain of biological fuels “competes for raw materials with other sectors, especially with the food industry, but also with the cosmetics and pharmaceutical products, bioplastics, and heating sectors. This affects the availability and market prices of these materials and can also raise ethical questions concerning the prioritization of food over fuels,” according to the document.
“Biofuels could also have a negative impact on the environment and climate. For example, biofuels derived from raw materials produced on arable land could negatively affect biodiversity, soil and water, and if these crops require additional land, there is a risk that emissions would not be reduced compared to those from fossil fuel use“
To sum up, conclude the members of the Court of Auditors, at present, in the EU, the future of biofuels in transport does not appear limpid,&strong> but characterised by a series of doubts and hesitations that will have to be resolved, to make way for well-considered choices, yes, but with long-term prospects.
The picture at international level, however, is different. Suffice it to mention that at the G20 meeting in New Delhi, 9-10 September 2023, it was announced The Global Biofuels Alliance (members include the World Economic Forum), the aim of which is “to increase global supply and demand for biofuels to accelerate the transition to zero emissions”.
On this matter, the International Energy Agency (IEA) estimates a tripling of global biofuel production across all sectors by 2030, with the USA, Brazil, and Singapore leading the way [source: “IEA shares recommendations for the Global Biofuel Alliance at G20 Energy Transitions Ministerial Meeting” – International Energy Agency].
From cellulosic biomass, biofuels that do not compete for raw materials with other sectors
As defined by the previously mentioned EU Directive of 11 December 2018 on the promotion of the use of energy from renewable sources, there are essentially three categories of biofuels, classified according to the raw material or technology used: biodiesel – obtained from rapeseed, sunflower, palm, and soy oils – and bioethanol, from corn, wheat, sugar beet, barley, and rye; so-called “advanced biofuels”, derived from waste and residues including algae, urban waste, non-food cellulosic materials, or lignocellulosic substances; biofuels produced – through mature technologies – from waste and residues such as used cooking oils, animal fats not suitable for food and animal feed.
Regarding “advanced” biofuels derived from waste and residues, research in the field of biotechnologies for bioenergy over the last decade has particularly focused on the strategic importance of cellulosic biomass [source: “Biofuels and Industrial Biotechnology” – International Centre for Genetic Engineering and Biotechnology].
Back in 2015, a publication in ScienceDirect – “New Paradigms for Engineering Plant Cell Wall Degrading Enzymes” – by the Weizmann Institute of Science, in Israel, and the Biosciences Center of the National Renewable Energy Laboratory, in Colorado (USA), defined cellulosic biomass as “the the most abundant natural renewable biological resource available on Earth“, precisely because it is found in those plant waste materials (grasses, agricultural waste, wood shavings), the use of which does not harm either the food sector (by taking land away from cultivation) or the energy sector, and does not involve ethical issues, especially for the most socio-economically fragile countries.
Biotechnologies for bioenergy: challenges in accessing the sugars contained in cellulose
On the subject of biotechnology for bioenergy, the authors of the publication on ScienceDirect, nine years ago, observed how cellulosic biomass is extremely difficult to degrade, acting as a kind of natural protective barrier against the plant material it covers:
“Research efforts to date have examined the diverse set of microbial strategies to understand how they gain access to the valuable sugars contained in cellulosic biomass in order to survive and thrive in their environment. Various paradigms of cellulolytic enzymes have been identified, including free enzyme systems, the cellulosome, multifunctional enzymes and cell wall-associated enzymes“
A team of scientists from the Lawrence Berkeley National Laboratory, within the US Department of Energy, in Berkeley, and from the Biological and Agricultural Engineering department at the University of California – Davis, in “Spatiotemporal dynamics of cellulose during enzymatic hydrolysis studied by infrared spectromicroscopy“, a paper that appeared in the first 2024 issue of the journal Green Chemistry.
“Cellulose is the tough tissue that makes up much of the herbaceous and woody plant bodies. It is a very rich, sustainable source of fermentable glucose from which biofuels can be made, but it is not easy to break it down into its composite sugars“
reiterates the study group. The long chains of glucose of which it is composed,’ he continues, ‘are intertwined with each other, giving rise to complex ‘string-like’ structures called ‘fibrils‘.
The hypothesis always held by biotechnologists is that these structures are the reason why the enzymes developed so far to degrade cellulose are so slow in their process, because the fibrils act as obstacles, as a ‘wall’ blocking access to the sugars that are enclosed in them. What strategies can be adopted today to make the process faster and more efficient?
Direct and real-time observation of the enzymatic hydrolysis process
In the field of biotechnology for the production of bioenergy by exploitingcellulosic biomass, the team made use of a technique developed at the Berkeley Synchrotron Infrared Structural Biology (BSISB) Imaging Program (which studies organisms and biomaterials in microscopic spatial dimensions), capable of combine the use of a microfluidic device and infrared spectroscopy to observe in real time how the enzyme works as it degrades cellulose.
The process in question is called “enzymatic hydrolysis” and, in this specific case, refers to the biological process that structures the cellulosic biomass to arrive at the sugars contained therein, which in turn can be fermented into biofuels [source: “Promoting enzymatic hydrolysis of lignocellulosic biomass by inexpensive soy protein” – Biotechnology for Biofuels and Bioproducts].
The aim is to understand exactly what happens during this process (and, if necessary, to intervene),’ explain the authors, ‘by collecting, in detail, “information on how the atomic structure of cellulose changes as the enzyme breaks it down‘. They add:
“The system consists of a small disc-shaped device with, inside, a small amount of fluid containing cellulose from green algae and a small amount of an enzyme derived from a fungus. The device shakes the two fluids together, allowing the reaction to begin, in the path of a powerful infrared light beam generated by Berkeley Lab’s Advanced Light Source, allowing precise, real-time snapshots of the fluid sample“
Detectors placed next to the device measure, at different time intervals, the way light is absorbed by combined fluids when they are along the direction of the beam: changes in spectral characteristics will indicate changes in chemical bonds or within the molecules themselves.
Glimpses of Futures
In the field of biotechnology for bioenergy, the approach illustrated here not only lends itself to application within other strands of biotechnology studies (e.g. on organic substances in soil, plant and animal tissue, particularly for biosafety issues), but also has the merit of enabling researchers to directly observe and control the ‘environment’ of the cellulosic biomass sampleduring its biological degradation.
What does this mean in concrete terms? To fully understand the whole process of enzymatic hydrolysis of cellulose, to study it closely in order to grasp any criticalities, to optimise it, to make it more agile, in an ever faster path towards the sugars it contains and, ultimately, towards their conversion into biofuels.
The goal is this: to increasingly produce sustainable energy from cellulosic biomass – cheaper, more abundant and more available than other types of biomass – by overcoming the age-old problems caused by the complexity of its structure, which does not facilitate access to the sugars trapped in it.
With the aim of anticipating possible future scenarios, we try to outline – using the STEPS matrix – the impacts that the technique developed to study in situ the destructuring of the cellulosic mass of waste plant material has on several fronts.
S – SOCIAL: more advanced biofuels, i.e. produced from waste and residues such as cellulose from waste plant materials, means less biofuels made from plant materials destined for the food sector, with the result of reducing the negative impact of biodiesel and bioethanol on agriculture, especially in the poorest areas, in the future – when world production of biofuels will double and triple, to fully adhere to global decarbonisation policies.
T – TECHNOLOGY: in the long run, the technique based on the combination of microfluidic device and infrared spectroscopy, to observe in real time the functioning of the enzymatic hydrolysis of cellulose, could cross over with artificial intelligence techniques and, more specifically, with artificial vision, for a complex and precise analysis of the changes occurring during the biological process, replacing the current detectors currently provided next to the device.
E – ECONOMY: In a future scenario, in which a major increase in the production of bioenergy from cellulosic biomass could become a reality, by virtue of the abundance and availability of this biomass compared to others and the evolution of technology for faster access to its sugars, the creation of new jobs will have to be envisaged, with people assigned to the collection and transport of those wastes and residues specifically intended for transformation into biofuels.
P – POLITICAL: Considering the specific reality in the European Union, the Parliament will, in the future, have to outline a clearer (and definitive) legal framework regulating the production and use of all biofuels (thus also advanced biofuels) in every sector, including the transport sector – so far lacking long-term strategies – given also the deadline, in 2035, which will mark the stop of petrol and diesel vehicles throughout the EU.
S – SUSTAINABILITY: long defined as the most abundant renewable natural biological resource available today, cellulosic biomass allows bioenergy to be produced sustainably, continuously and without depleting the planet’s resources. The evolution of biotech techniques that optimise access to the sugars it incorporates would, in the future, have a profoundly positive impact in terms of environmental, as well as social, sustainability.
