直播回放 | 未来绿色能源范式：电化学与生物质能 | 前沿面对面

Frontiers: Dear Professor Uwe, as you mentioned in your presentation, water has several disadvantages as the reaction medium; what is the challenge to avoid this kind of problem？

Prof Uwe Schröder: It doesn't have so many disadvantages. The one disadvantage that I mentioned is that when it comes to oxidation and production reactions, which are very close to the decomposition of water, the actual water decomposition competes with the electrosynthesis process. But it is not so difficult, especially for hydrogenation. It is kind of an interesting approach simply to use a high current concentration of your organic precursor. You would like to apply this in an industrial process anyway because you want to have a high concentration to get a product yield, product turnover or product formation rate. So that is not so much a problem.

There is one issue that I would see from a sustainability perspective, which is that, in the end, you might have a waste stream that consists of water (the aqueous electrolyte phase) plus organics. It is very often tricky to handle waste because organic streams can be actually burned, and aqueous waste streams go into wastewater, but having these mixtures might be a problem. This is why it is important to run these processes in a continuous manner with an electrolyte solution recycling. So you don't produce this much of a cruise waste stream. That is the second issue. Otherwise, I do see lots of disadvantages to using water actually.

Frontiers: Harvesting energy from wastewater is an important topic to pursue, given the amount and extent of wastewater. However, there are various types of wastewater with constituents that can destabilise or destroy the microbial system. Would you like to suggest how these challenges may be overcome economically and sustainably?

Prof Uwe Schröder: That is an absolutely valid comment. When I talk about wastewater, I usually refer to municipal wastewater, which is wastewater from mainly households. That is usually relatively stable in terms of bacterial growth conditions. But you are right; when it comes to industrial wastewater, it becomes much more complex. We conducted a series of tests with industrial wastewater. In such cases, you may want to get the bacteria (with which you want to inoculate your microbial fuel cell) from the respective wastewater treatment plants. It's really interesting because, in many of these conditions, you may have a lot of extremophiles—bacteria that can withstand very toxic conditions, high metal loads, and acidic or alkaline conditions.

We found that using the inoculum from the wastewater treatment of their industrial waste helped us treat their wastewater. Of course, there are still issues with sturdy or recalcitrant compounds that may not be treated satisfactorily, but that is a common problem in every wastewater treatment system. My first advice would be to use bacteria from the waste stream itself. This is always a good idea because the bacteria build up food webs in their native environment. So, when you want to treat wastewater, you should go directly to the factory's wastewater treatment plant.

Nevertheless, I think municipal wastewater treatment should be the primary target for this kind of technology. However, it would also be beneficial to see this technology applied to industrial or harsher conditions.

I hope this answers the question.

Frontiers: Dear Professor Yang, You have introduced some innovative technologies combined with thermochemical conversion; what is the most promising one, and what is the challenge if applied in the industry?

Prof. Haiping Yang: For combustion, Biomass is only burnt for heat, allowing us to generate power or heat water. Chemical conversions are more complex, but some are promising. Nowadays, gasification may be the better option for industrial commercialised applications. The reason is that we produce syngas that can be used for Fischer-Tropsch synthesis with gasification. This synthesis is more efficient. However, in industrial applications, biomass gasification typically uses air, resulting in a low heating value of around 5-6 MJ per cubic meter, which is quite low. Using steam or oxygen can improve the heating value and increase the cost. However, policy and technological advancements assist with these challenges, suggesting a faster development pace. When combined with the current trend of green methanol initiatives and the production of green jet fuel, biomass gasification becomes particularly promising.

Producing chemicals might be easier and faster through pyrolysis. However, this process involves challenges such as high temperatures and the production of various difficult products to separate. For improvements, catalysts can be employed. Special catalysts can help produce specific chemicals, such as aromatics from biomass pyrolysis. This is being implemented in New Jersey and Georgia, where companies use catalysts like zeolites to produce these chemicals.

While gasification is highly promising for commercialisation, challenges like cost and product separation remain. However, with ongoing technological advancements and catalyst development, the potential for biomass as a green energy source looks bright.

Frontiers: To derive different types of fuel and materials, do you use different types of biomass sources? Please comment. Also, as a natural resource, there is considerable variability in biomass properties. How do you overcome that issue when producing your products?

Prof. Haiping Yang: Yes, different types of biomass have varying compositions and compounds, which influence the final products. Additionally, the activity levels of these biomasses differ, requiring different temperatures or processes. In my work, I primarily use gasification and pyrolysis, which involve high temperatures.

For large-scale gasification, removing moisture from the biomass is important. Although there are some variations in biomass properties during the gasification process, it typically reaches a stable level suitable for processing different types of biomass.

In the case of pyrolysis, specific types of biomass like kiwi fruit peel, banana peels, or eggshells—used for producing specialised chemicals or active sites—contain unique compounds such as proteins found in algae. These proteins need to be preserved to produce certain speciality products.

To produce specific chemicals or active sites, the unique properties of the biomass must be maintained. However, to produce a uniform product, we usually treat the biomass to ensure stable conditions and consistent properties throughout the process.

再次感谢Uwe Schröder 教授和杨海平教授的精彩分享，请大家持续关注 Frontiers Conversations（前沿面对面）的后续活动。

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