The proposed project aims at drawing a conceptual model to estimate the environmental profile of H2 and CH4 production through dark fermentation. Specifically, the project will be focused on the accounting of CO2 emissions and savings for each unit operation of the combined process, with the purpose of estimating and quantifying the carbon footprint in different configurations. To this regard, a life cycle approach will be adopted to estimate and quantify the carbon footprint of the process, including namely the direct/indirect CO2 emissions and the CO2 savings from compost utilization in agricultural applications, reuse of other valuable products (if any) in industrial processes and biogas exploitation for energy production. Internationally recognized methodologies for the accounting of CO2 emissions and savings will be applied, which will provide the expected results a wide validity and replicability even in trans-national contexts.
As mentioned above, the main novelty of the proposed research relies on a holistic assessment of the contribution of biological H2 and CH4 production to the carbon footprint of biowaste management strategies. It has already been pointed out in the previous sections of this proposal how individual processing technologies for biowaste treatment have been widely investigated from the process engineering perspective, but mainly as stand-alone processes. Combinations of different treatment stages to maximize the rate of materials and energy recovery from the biowaste have also been intensively investigated, although a still open issue involves the correct and thorough definition of the mass and energy balances of the whole process, which are in turn closely related to the specific process layout concerned. Multi-stage or hybrid layouts which involve the combination of various processing phases/technologies may indeed display rather different yields of conversion into the desired products (biofuels, biomaterials, etc.) depending on which mainstream is followed. As a result, the definition of the materials and energy flows for the process layout of concern requires some significant knowledge and expertise stemming from the experimental results available in the literature, along with some additional effort to derive both theoretical relationships between the relevant parameters and a conceptual description of the process. To the proponent¿s knowledge this is at present scarcely available in the scientific literature and is on the other hand strongly required to perform any environmental analysis of the process. Therefore, one first novelty of the proposed project is a critical interpretation and conceptual description of the experimental results of previous studies on bio-H2 production using multi-stage/hybrid schemes, identifying the effect of the key process parameters on the conversion yields and describing these by means of theoretical modelling.
Such preliminary evaluations will then be used as input data to the conceptual model that will be built to estimate the environmental profile of bio-H2 production in different process configurations. A life cycle approach will be adopted to estimate and quantify the carbon footprint of the process, including namely the direct/indirect CO2 emissions and the CO2 savings from compost utilization in agricultural applications, reuse of other valuable products (if any) in industrial processes and biogas exploitation for energy production. This represents the second main innovation of the proposed project, and the completion of this task is believed to provide some significant advance in the status of the current knowledge of the topic. In particular, at the moment a systematic study concerning the environmental assessment of bio-H2 production in combination with other process stages is still missing, so that the proposed project is specifically meant to fill in this gap.
A further added value of the work will result from the fact that internationally recognized methodologies for the accounting of CO2 emissions and savings will be applied, which will provide the expected results a wide validity and replicability even in trans-national contexts.