Professor Damien Batstone speaks to AZoCleantech about his game-changing research on how sugarcane can be used as a clean energy source to produce hydrogen.
What drove your research into sugarcane as a clean energy source to create hydrogen?
We had previously researched the conversion of sugarcane into alternative products (such as biopolymers) and found this to be highly favorable economically. Whereas sugar production utilizes bagasse as thermal energy, this is a residue when making biopolymers, liquid sugar, or ethanol. This residue can then be used for electricity generation or alternative energy products such as hydrogen.
What makes sugarcane a suitable resource that could revolutionize hydrogen production?
We are using the bagasse fraction, as the juice fraction can be utilized elsewhere (e.g., for ethanol or biopolymer production). Very few other crops result in such a huge and relatively reliable amount of biomass, making it ideal for large-scale hydrogen production.
Can you explain the processes your team has used in its research?
We investigated two technologies. Thermal gasification is a dry process and is carried out at a high temperature. The bagasse is dried, and then incomplete combustion results in a mixture of gases, which further react to hydrogen and carbon dioxide. The carbon dioxide is extracted (and may be captured for storage), leaving the hydrogen as a product. We also investigated hydrothermal gasification, which is a similar reaction, but at high pressure and in wet conditions. This avoids needing to dry the bagasse before processing.
Would the use of sugarcane to make hydrogen be a costly process? Could this technology be adopted on a much larger scale?
Based on our economic analysis, the process can make hydrogen at $1.5-$3/kg, which is a lower cost than any other form of non-fossil hydrogen. It can be made at an even lower cost if we do not produce the hydrogen at high pressure. This technology is only applicable at a larger scale (500+ t bagasse per day), and we have evaluated up to 2500 t bagasse per day. For reference, the lower scale is a moderate-sized sugar mill, while 2500 t/d is the largest-sized sugar mill.
Professor Damien Batstone has revealed that sugarcane could have significant environmental benefits when used to produce hydrogen. Image Credit: Yatra
What happens to the carbon dioxide produced during production?
It is currently separated from hydrogen as a sour gas stream (which also includes sulfides). This can either be geo-stored or used industrially.
This research offers the potential for positive environmental benefits if adopted on a larger scale. Please can you explain this in more detail?
It represents a sustainable source of low-cost hydrogen while offering the ability to fix the carbon-dioxide for industrial use or long-term storage.
How would cane growers benefit from this alternative pathway for the industry?
Cane growers and mills are highly exposed to world commodity sugar pricing, with the cost of production often exceeding sugar prices. Producing alternative products from juice (such as biopolymers or fuel) while processing the bagasse into hydrogen provides improved profitability. A hydrogen production hub also provides improved regional benefits, including an industrial base and employment.
Why is this research important for the wider hydrogen production industry?
As an important future energy carrier and major industrial input, continuity and diversity of non-fossil hydrogen production is essential. The only other major source of non-fossil hydrogen is renewable electricity, which is subject to spot pricing fluctuations and variation in supply. We also produce it at a far lower cost and potentially at a larger scale than electrolytic hydrogen.
Why is hydrogen important for the future of converting unusable energy? How does this research project fit into this?
Hydrogen converts electricity and otherwise unusable energy to a highly versatile, clean, chemical energy source. It is the best way to decarbonize the industrial chemical ecology, including clean metallurgy, vehicle fuels (conventional and emerging, including hydrogen directly), fertilizer, plastics, and commodity chemicals. It can even be used to make food. While it can be transported, as a highly compressed gas or liquid, or as liquid ammonia, one of the best ways to use it is to connect a hydrogen producer directly to the end-user.
What challenges have you faced during your research and how were these overcome?
The technology is relatively conventional, given it has been used in coal gasification for over a century, and some challenges (e.g., the formation of toxic byproducts) are mitigated by the clean nature of bagasse. Key challenges relating to the high-pressure process included the limited availability of materials capable of withstanding high temperatures and pressures. This increased the cost of the hydrothermal process substantially. We also found that the need to compress hydrogen for sale was an economically limiting factor.
How can farmers and sugar companies go about applying the research findings to their businesses in the future?
A future project will be large in scale and will involve the direct involvement of growers, sugar companies, and likely end-users. It will also include governments investing in a hydrogen economy, incentivizing the industry, and improving the sugar industry's economic sustainability. Sugar companies are already assessing the technology, and farmers should assess future technologies and product streams.
What are the next steps for the project?
A position paper is being produced in Q1 2021, which will present the study's aggregate outcomes and be made publicly available. Outcomes from the work are currently being provided to sugar companies.
Where can readers find more information?
About Damien Batstone
Professor Damien Batstone leads environmental biotechnology and resource recovery research programs at The Advanced Water Management Centre, The University of Queensland, Australia. Research work has focused on renewable energy from biomass, the production of commodity chemicals from renewable sources, and the water-energy-food nexus, including the production of novel feeds for aquaculture from gases such as hydrogen. He coordinated the final year undergraduate chemical engineering design course at UQ from 2017-2020, in which 150-200 students design a novel process from concept to final design. The 2020 design challenge was hydrogen from bagasse.
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