Across Europe, industry is under pressure to cut emissions, lower dependence on fossil energy and use renewable resources more intelligently. Within that context, the EU-funded CERNET project is exploring how biogenic CO2 and methane can be converted into high-value bio-based ingredients and materials. One of the project's latest deliverables, D2.2 - Energy audit and guidelines for clean energy inputs - takes a close look at the energy demand of CERNET's four bio-based value chains and examines where renewable energy could realistically be introduced.

A closer look at energy demand across four value chains

Deliverable D2.2 builds on the system mapping and early mass-and-energy assessments prepared in D2.1. Based on that groundwork, the task team led by BER carried out an energy intensity audit for all four bio-based value chains, calculating how much primary energy is needed to produce 1 kg of each final product, including L-alanine, sorbitol, L-malic acid, PHA and ectoine.

To make the results comparable across countries, all energy inputs were standardised using Primary Energy Factors (PEF) for electricity, heat and cooling. This made it possible to compare processes in Italy, Spain, Slovenia and Bulgaria on the same basis.

The work also captured several energy exchanges that had not been included in the earlier model, such as CO2 compression, biomethane drying and additional heating and cooling requirements linked to fermentation. As a result, D2.2 provides the most complete picture so far of energy use across CERNET's conversion routes.

Where is renewable energy most relevant?

A key part of D2.2 is not only measuring current energy demand, but identifying where renewable electricity, renewable heat and green hydrogen could be integrated in practice across the four value chains.

Each process step was grouped into one of three implementation levels:

• Low difficulty: renewable integration is relatively straightforward, for example in electrically driven compressors or cooling equipment.
• Medium difficulty: integration is feasible, but may require supporting measures such as storage, buffers or operational adjustments.
• High difficulty: integration is harder because the process depends on stable, uninterrupted operation, as is often the case in fermentation.

For each value chain, the deliverable estimates:

• potential savings in primary energy,
• changes in carbon intensity, and
• the achievable Renewable Energy Rate (RER).

Together, these results show where renewable inputs can make the biggest difference and where implementation is likely to be more demanding.

Main findings from the energy audit

Value Chain I - Protein hydrolysate and L-alanine (biological route)

Value Chain I showed clear potential for replacing conventional energy inputs with renewable alternatives. Updated process data reduced the estimated energy intensity compared with the first model, and the results indicate that medium-level RES integration can significantly lower both primary energy use and carbon intensity.

Value Chain II - Methanol platform to L-alanine, sorbitol and L-malic acid

These pathways remain energy intensive, mainly because of fermentation steps and methanol-based conversion processes. Renewable integration is more technically demanding here, but the analysis still shows meaningful energy savings at medium implementation level, particularly because electrolyser inputs have such a strong influence on the overall balance.

Value Chain III - PHA production (biological route)

In Value Chain III, a large share of demand comes from compression and cooling. Fermentation is again one of the more difficult areas for renewable integration because the process must run continuously. Even so, higher levels of renewable uptake reduce carbon intensity and create noticeable primary energy savings.

Value Chain IV - Ectoine from methane (biological route)

Value Chain IV has the lowest overall energy intensity of the four. It contains relatively few high-demand steps, which makes it especially suitable for early renewable energy uptake. The analysis shows that even low-difficulty RES measures can quickly improve the energy profile of this route.

Hydrogen matters - especially in two value chains

Two of CERNET's value chains, VC I and VC II, depend on green hydrogen produced via proton-exchange membrane (PEM) electrolysers. D2.2 is the first project deliverable to quantify the energy demand of that hydrogen production step and assess its impact on carbon performance.

The results show that the source of electricity used for electrolysis is critical. When electrolysers run on renewable power instead of conventional grid electricity, carbon intensity drops substantially and the upstream primary energy burden is reduced accordingly.

Why this matters for CERNET

The findings in D2.2 provide useful direction for the next phases of the project:

• They show where renewable integration can have the strongest effect, including electrolyser operation and major thermal loads.
• They point to the value chains that may offer earlier opportunities to reduce fossil-based energy demand.
• They provide input for technology optimisation in WP3, WP4 and WP5, and support the sustainability work in WP6 as well as upscaling activities in WP7.

Overall, the analysis underlines that renewable energy is not a side issue in CERNET. It is central to whether the project's conversion routes can deliver credible long-term sustainability benefits in both energy and climate terms.

A stronger basis for renewable-powered bio-based production

D2.2 is an important step for the CERNET project. By clarifying where energy is used, where the main pressure points are, and where renewable inputs are most realistic, the project now has a more solid basis for designing efficient and lower-carbon bio-based production routes.

As CERNET moves into its next stages, this knowledge will help shape demonstration activities and support the wider ambition of turning biogenic gaseous carbon into sustainable, high-value ingredients and materials for Europe.