Good questions!

First, with respect to the gasification process to produce syngas (a mixture of H2 and CO) , the challenges would be:

1) Energy intensity (such as steam generation, etc.) for the gasifier.

2) May need to separate sulfur and particulate matter (PM) from the syngas.

3) If the purpose is to produce H2 gas, then you will need a water-gas shift (WGS) reactor to convert CO using steam (in presence of a catalyst) to CO2 an H2. Then you need a separation technology to separate H2 from CO2 (and a disposal method the latter gas, viz., CO2).

Second, with respect to the anaerobic digestion, the challenges would be the process efficiency and separation and purification of the produced biogas (primarily CH4). Again, you will need to separate sulfur from the produced biogas. There are other needed improvements to the anaerobic digestion process.

Hope you find this note helpful.

I think, for this case, price of the fuel and cost-benefit are very challenging issues. Climatic conditions, Frequency of production and availability of resource are also very important.

It,s really a valuable question. The main challenges are:

1-Technical expertise lacking & poor assistance

2- No performance evaluation (methane leaks, fertilizer quality?)

3- Substrate & water availability

4- Substrate quality and quantity

5- Lack of awareness of the importance of waste management

6- Lack of planning capacities

7- Cost for energy up-gradation and delivery too high

Thank you all for the interesting feedback and answers.

Dear Yehia F. Khalil , since you mentioned sulfur removal from biogas but there are a lot of industrial-scale plants for biogas purification (sulfur below 10 ppm is obtained), why do you think it is still an open challenge? How should this technology be improved in your opinion?

Dear Rachan Karmakar , I agree with you on the open problem of biomass seasonality: will it be efficiently tackled by co-digestion and logistic improvements, or do you think that some totally novel approaches should be investigated?

Dear Muhannad Malandi , I also think that points 2 and 7 (CH4 leaks and energy cost of CO2/CH4 separation) will be the main challenges at a global level: and after all, these are two aspects of the same problem, namely minimizing GHG emissions. On the other hand, you are right to highlight the points 1 and 5 which are the main barrier in developing countries: how can these problems be addressed in your opinion?

A challenge and an opportunity is to take advantage of the synergies between anaerobic digestion, gasification and Power-to-gas. Heat integration seems to be a first step especially if you need to heat the digester, dry the digestate and/or regenerate the scrubber liquid in case of amine based biogas upgrading. Separated CO2 from AD/upgrading and gasification/methanation as input for Power-to-gas. Use the microbial consortia in the digester to convert nitrogen free syngas from gasification to methane. Lower the specific investment cost in upgrading and downstream processes by combining AD, gasification and Power-to-gas.

Valerio Paolini Sir, I think more logical research should be there. The problem we can discussing about can only be done if novelty is there in the approach of the researchers. Completely new approaches are obviously required. Otherwise we cannot move further. But logistic improvements are also required. Many of the research works are there which are going on are very effective. They should be supported and carried on.

Research should not be done only towards the treatment of organic wastes or the optimal generation of biogas, the integration of both goals should be sought. The goal is to make anaerobic digestion a good strategy for the final disposal of organic wastes and, at the same time, making it competitive against conventional electric generation processes. Greetings.

A very good question @ Valerio Paolini. In my field, one of the final challenges is the development of biological based analyses capable to predict the performance of anaerobic digesters in order to take correct operational desisions. Specifically, the finding of biological markers (microorganisms, genes or metabolites) that can be used as early warning of system´s failure. Up to date, there are a lot of works dealing with this, but there is still a gap and bias in the technologies used to this porpose (mainly the sequencing technologies and bioinformatic tools).