The importance of nitrous oxide in compost and biomethane production: a general reflection arising from the life cycle approach of an AIMAG project.

The production of biomethane in biodigestors dedicated to the treatment of FORSU by anaerobic-aerobic means is a well-established reality in Italy, undergoing further expansion due to:
1) Need for energy (better if renewable);
2) Large quantity of FORSU to be treated but lacking implants.
Nevertheless, the sustainability of fuels must be respected (RED-2 Directive), which governs the granting of incentives also to biomethane. The government would be ready to review the draft decree on incentives to biomethane following appeals from industry operators. “There is a supplementary assessment concerning plant projects using the Organic Fraction of Urban Solid Waste (Forsu) .” However, the contribution of these types of plants should not only be assessed for the treatment of FORSU, the power generation and the sustainability of the biomethane line alone, but also for the impacts of compost production.
AIMAG has been involved in this field for a long time and with the plant of Finale Emilia (70,000 tons of FORSU treated/year and about 3,000,000 smc biomethane produced) is benefiting from the incentives of the GSE. AIMAG is therefore always looking for the best ways to make the management of anaerobic treatment sustainable, adopting an LCA approach to the treated FORSU and the biomethane produced. Indeed, the new regulations (EU and ITA) could also assess the sustainability of the related aerobic line, which leads from digestate to compost production.
In this respect, not only is very important the management of nitrous oxide (N2O), paying attention to all the process steps that can potentially affect this production, but it can be interesting to better evaluate the importance of the quality of the compost produced.
Firstly, by looking at the actual quality and fate of the compost produced, since non-specific compost often ends its life in landfill and this is not a correct way to implement the principles of the circular economy.
Secondly, by observing the percentage of humic acids and fulvic acids which by their nature, having a degradation time of more than 100 years, in a LCA logic may not be counted as C-biogenic and may be counted among the factors contributing to the “sink” effect, i.e. reservoirs of C.
Thirdly, by observing all the phases that, with greater or lesser emphasis, affect the carbon footprint of the compost produced and therefore of the whole activity.
It would therefore seem appropriate to consider how to promote this quality of compost.