A project developed by Ainia Centro Tecnológico leverages two of the by-products from the production of biogas (the digestate resulting from anaerobic digestion and the CO2 from combustion) to grow microalgae. In turn, the microalgae serve as a feedstock for the biogas plant. Researchers at this technology centre in Paterna (Valencia) highlight that this technique improves the efficiency, profitability and sustainability of such facilities.
Science has just presented a new argument justifying the appropriateness and feasibility of building agribusiness biogas plants: the possibility that some can serve to produce digestate and CO2 that can then be used to cultivate microalgae, the biomass of which can be used to produce certain biofuels. Ainia Centro Tecnológico aims to demonstrate this technique through the Algamet project, which aims to "develop techniques for growing microalgae from waste streams from the production of biogas, and then using the algal biomass as a substrate to increase the productivity of biogas plants".
Jorge Bauzá from Ainia's Environment and Quality Department explains that "the project aims to generate a co-substrate (microalgae) in low-cost systems to boost the efficiency and sustainability of biogas plants without competing with food crops". Ainia has found that both the digestates (which have a high nutrient content) and the CO2 (from biogas combustion) provide two of the four essential elements needed to grow photoautotrophic microalgae: nutrients, CO2, water and light. The centre adds that "it has been confirmed that certain species of microalgae achieve high growth rates using these waste streams, provided they have enough light".
No need to look far to find the ideal microalgae
"Microalgae have been selected and grown from various media naturally colonised by algae (standing water, sewage, etc.) to assess, among other things, their resistance to environmental factors, their ability to consume nutrients, their growth kinetics or their potential for producing biogas," explains Bauzá. For this researcher, "there is no single ideal type of microalga with high growth rates, high levels of resistance to environmental factors and which provides large amounts of biogas per unit of mass, but in general there are several, including autochthonous microalgae that are generally better suited than laboratory species".
This is not Ainia's first experience in this field. The centre is leading another project (Integral-b) focused on producing biodiesel from used vegetable oil in a pilot plant that receives its electricity and heat from a biogas process. In turn, the biogas process is fuelled using the by-products of the biodiesel plant, mainly glycerine, as well as other organic waste from the hotels, restaurant and catering industry. This is yet another example of how the circle of sustainability can be closed through bioenergy production. The Algamet project is funded by the Valencia regional government's Institute for Small and Medium Industry (Impiva) and the European Regional Development Fund under the programme of support for R&D aimed at technological institutes
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