Dear friend Carlos Roldán-Blay

Thank you for sharing your insights on the integration of biogas and photovoltaic (PV) systems within rural microgrids. Your work raises several thought-provoking points regarding the potential of hybrid renewable energy solutions to address the unique challenges faced by underserved communities.

To further explore the broader implications and challenges of your study, I would like to pose a few questions for your consideration. Firstly, what makes the combination of biogas and PV systems particularly compelling for rural electrification? Are there specific attributes of these technologies that enhance their complementarity in terms of mitigating intermittency, reducing costs, or minimizing environmental impacts?

Additionally, have you reviewed approaches from other regions where similar hybrid systems have been implemented? It would be valuable to learn whether there are historical or contemporary examples that demonstrate the successful stabilization of power supply through the integration of biogas and other renewables in rural settings.

I am also interested in your perspective on the primary barriers to adopting such hybrid systems. In your view, how do factors like feedstock availability, policy frameworks, community engagement, and technical capacity influence the feasibility and scalability of these solutions? Furthermore, when considering alternative bio-based options for hybridization, what criteria guide your assessment of their effectiveness relative to biogas, and are there promising technologies that stand out in particular environmental or socioeconomic contexts?

Lastly, could you elaborate on how you evaluated the hybrid system’s performance in meeting peak demand within your study? Were there specific metrics or findings that highlighted either the strengths or areas for improvement in your approach?

I look forward to your reflections on these questions, as they could provide valuable insights for advancing the application of hybrid renewable systems in diverse rural environments.

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Best regards,

Kaushik

Hi again Carlos Roldán-Blay

As replied earlier, I fully agree with your conclusions about biogas. Since 1979 we help a broad range of industries and utilities worldwide to decarbonize and get more resilient, self-reliant and circular in both energy and water in the most sustainable way. We do this by converting their organic waste streams to steady 24/7 circular biomethane H2-C-H2 (biohydrogen H2 + circular carbon C) to replace fossil fuels for heat and power generation, to clean water for reuse and to active biofertilizer for healthy soils and crops. Hence up to 100% circular water & energy solutions. One of our first projects was on an island in The Philippines which was depending on over sea fossil fuel for its energy. Today we convert up to 90% of the organics (COD, TOC) to biomethane.

We don't publish our research and development but we can share our recent case study on converting waste from biofuel production to biomethane with low cost buffer storage and on-demand up to 15 MW power generation injected in the HV public grid.

Dear Kaushik Shandilya,

Thank you for your thoughtful and enriching comment on our work.

We chose to combine biogas and PV in our study because of their natural complementarity: while PV is intermittent and only produces during daylight hours, biogas can provide continuous energy supply, especially during night hours or cloudy days. This synergy makes the hybrid system more robust and suitable for rural electrification where reliability is critical.

Although our work is based on simulations, the case study refers to a real location in Spain: Aras de los Olmos, a remote rural village where the photovoltaic plant is already installed and in operation. Furthermore, as part of a broader research effort, we have built a small-scale biogas pilot plant to validate our simulation results and explore the viability of local organic waste as feedstock.

The model incorporates actual demand profiles and climate data, and includes an economic analysis and performance evaluation focusing on reliability and cost-efficiency (see Tables 2 and 3, and Figures 6 and 7 of the article).

The main barriers we identified are:

• Availability and logistics of feedstock for biogas systems (our model assumes an optimized and constant yield);
• The initial investment needed for hybridization;
• The need for technical capacity-building in rural communities.

We agree that policy frameworks and community involvement are crucial to the adoption and scaling of these solutions, although these aspects were not directly addressed in our publication.

To assess system reliability, we used indicators like Loss of Load Probability (LOLP) and autonomy ratio, which quantify how well the system meets energy demand under varying conditions, including peak hours.

We appreciate the references you shared and look forward to reviewing them. Let’s keep this conversation going—advancing hybrid renewable energy solutions in rural contexts is both a technical and social challenge, and collaboration is key.

Best regards, Carlos Roldán-Blay